GULF RESEARCH REPORTS Vol. 9 No. 1 January 1994 ISSN: 0072-9027 Published by the f GULF COAST RESEARCH LABORATORY I Ocean Sprinas, Mississippi Gulf Research Reports Volume 9 | Issue 1 January 1994 Historic Trends in the Secchi Disk Transparency of Lake Pontchartrain J.C. Francis University of New Orleans M.A. Poirrier University of New Orleans D.E. Barbe University of New Orleans VWijesundera University of New Orleans M.M. Mulino Steimle and Associates, Inc. DOI: 10.18785/grr.0901.01 Follow this and additional works at: http:/ / aquila.usm.edu/ gcr Part of the Marine Biology Commons Recommended Citation Francis,}.; M. Poirrier, D. Barbe, V. Wijesundera and M. Mulino. 1994. Historic Trends in the Secchi Disk Transparency of Lake Pontchartrain. GulfResearch Reports 9 (l): 1-16. Retrieved from http:// aquila.usm.edu/gcr/vol9/issl / 1 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean Research by an authorized editor ofThe Aquila Digital Community. For more information, please contact Joshua.Cromwell^usm.edu. Gnif Research Reports, Vol. 9, No. 1, 1-16, 1994 Manuscript received March 3, 1993; accepted September L3, 1993 HISTORIC TRENDS IN THE SECCHI DISK TRANSPARENCY OF LAKE PONTCHARTRAIN J.C. FRANCIS', M.A.P01RRIER‘,D.E.BARB^:^V.WUESUNDERA^ AND M.M. MULINO’ ^Department ofDiotogicat Sciences, University of New Orleans, New Orleans, Louisiana 70148 ^Department of Civil Engineering, University of New Orleans, New Orleans, Louisiana 70148 ^Ste 'unle and Associates, Inc., Metairie, Louisiana 70004 ABSDiACT A major cnvironmenlal concern nboul Lakc Ponlchartrain is an assumed iong-icrm increase rn turbidity based on Secchi disk transparency obscrvalions. Regression of the available data on Sccchi disk, transparency versus lime (1953 through 1990) reveals a slatislically significanldecreascin transparency of about -40%. However, the data set is biased In that it does not adequately represent the seasonal effects of salinity and wind speed. Two analytical procedures were undertaken to determine the extent to which the apparent long-term decrease in transparency was dependent on the seasonal bias. One procedure involved sca.SQnal adjustment of the data for the effects of salinity and wind speed. The otlier procedure was to remove the seasonal bias by consirucling unbiased data sets. Seasonal adjustment for the effects of salinity and wind speed reduced the level of significance for the relationship between Sccchi disk transparency and lime from about 1% to about 10%. This result indicates that some of the apparent decrease in transparency in the original data is the result of inadequate representation of seasonal effects in the biased data set. In most years data are not available for all months with the result that the seasonal effects of salinity and wind speed are not adequately represented. When the bias was removed by constructing unbiased data sets, the data no longer supported the conclusion of a statistically significant change in Sccchi disk transparency from 1953 to 1990; p>0.5. IlSTRODUCnON Lake Ponichartrain is an einbaymenl in a large estua- rine system in southeastern Louisiana. Il has a mean salinity of 4 ppL a mean depth of 3.7 m, and a surface area of 1630 Saline water enters from adjacent estuaries through tidal passes. Fresh water sources are streams. New Orleans area outfall canals, and the Mississippi River during open- ing and leakage of the Bonnet Carrd Spillway (Barb6 and Povrricr, 1991). Over one million people live on the southern sliore of Lake Pontchar train. With increasing urbanization of the New Orleans area over the last century, concerns have arisen as to possible declines in water quality, fisheries, recreational use and commercial valueof theesiuary (Houck et aL, 1987). Increased lurbidiiy, for example, is regarded as an environmental problem in Lake Ponichartrain. Sup- port for iJiai concern is provided by Stone ei al. ( 1 980) who plotted four sets of selected Secchi disc transparency data from Lake Pontchartrain and concluded that water clarity had decreased by almost 50% between 1953 and 1978, Although Stone's report (Stone ei al., 1980) is often cited as indicating a major environmental change in Lake Pontchartrain, il did not mclude all available data or address die seasonal effects of wind and salinity on transparency values. Thompson and Fitzhugh (1985) found a relation- sliip between sal inity and lake clari ly w iih Lake Pontchartrain being clearer during periods of higher salinity and more turbid during fresher periods. Swenson ( 1980), found that winds blowing over Lake Poniciiamain are sufficient lo stir and mix bottom sediments ihrou ghoul the water column about 15% of the time. Thompson and Verret (1980) reported that occasional high winds during frontal passages, and at other limes, are capable of resuspending bottom sediments, especially in the winter. Dow and Turner (1980) also slated that turbid conditions may be caused by weather fronts and their wind systems. Storm-water runoff from the New Orleans area is currently discharged into Lake Pontchartrain without any treatment. Although the potential contribution of urban runoff lo the pollution of estuaries has been recognized for some time, few studies have actually documented specific adverse effects (Odum and Hawley, 1987). On an annual basis, pollution from urban runoff can contribute more suspended solids and plant nuirienis than any other pollu- tion source (Scheaffer et al., 1982). Urban runoff could 1 2 Franqs ft al. affect the Secchi disc transparency of Lake Ponichartrain Uirough the introduction of plant nulrienis which increase phytoplankton growth and by the introduction of suspended solids (Mancini and Plummer. 1987; Odum and Hawley, 1987). It is cunentJy assumed that the turbidity of Lake Ponichartrain has increased by almost 50% between 1953 and 1978 (Slone et al., 1980) due to the activities of man. Our study includes recent data, investigates the effects of salinity, wind and seasonal differences on transparency and tests long-tenn trends for statistical significance. The study was designed to provide a better understanding of trends and how natural factors affect water clarity. ResulLs of this study will provide realistic goals for the treatment of urban runoff in plans to restore Lake Ponichartrain. Materials and Methods Description of the Database The Secchi disc is widely used to estimate the depth of light penetration in aquatic habitats (Tyler. 1968). All data used in this study were obtained with a 20 cm disc with black and white quadrants. The raw data used in this study consisted of observations of Secchi disk transparency and salinity recorded by several investigators during the periods shown in Table L This data set contains Secchi disk transparency and salinity data from July 1953 through December 1990. In some years, data are not available for several months. For most months, data were only collected once amonth. Data collected by the Louisiana Department of Environmental Quality from 1985 through 1990 were recorded from the Causeway Bridge, which is about 20 feel above the water surface. Therefore, their transparency values may be lower because of the greater distance be- tween the observer and the water surface. In summary, the data set is incomplete: • It does not contain data for all years. • It does not contain data for all months. • It may not be representative of particular months because data were collected only once or twice a month, • U is not consistent witli regard to station location. Wind data used in this study were taken at New Orleans Intemadonal Airport bom 1953 through 1990 and published in Local Climatic Data by the National Weather Service Meteoro- logical Observation Office. The elevations at which the wind data were measured were not the same in all years. The data from January, 1953 to July, 1969 were taken at an elevation of 3 feet abovelhe ground, and iheoihcrs at aneievalion of 4 feet. TABLE 1 Sources of Secchi disk transparency and saKnity data. Investigators Period N* Sullkus el al. (1954) 8/19/53 - 6/30/54 155 Stern and Stem (1969) 6/2/69 - 7/22/69 71 Dugas and Tarver (1973) 3/18/70 - 5/18/71 109 Tarver and Savoie (1976) 9/26/72 - 8/22/74 279 Poirrier et a/. (1975) 7/17/73 - 11/1/73 73 Stone et al. (1980) 1/78 - 12/78 219 0‘Hara and Capello (1988); Louisiana Department of Environmental Quality (LADEQ) (unpublished 3/31/82 - 1 1/29/82 456 1/4/83 - 12/7/84 816 daut) 7/8/85 - 8/14/90 311 Steiinle and Associates (1985) Western lake 1/12/84 - 10/25/84 168 Eastern lake 2/16/84 - 11/1/84 149 * Number of observations Secchi Disk Transparency 3 The salinity data sei, STORET, obtained from the U.S . Army Corps of Engineers contains data from 1953 through 1980, and from 1986 through 1989. These data were only used in analysis of variance to determine the statistical significance of armual seasonality in salinity. Statistical Methods All criteria were met for application of parametric staiis- Ucal methods. Simple and multiple regression analyses and the analyses of variance were performed according lo standard procedures as described in Sokal and R ohlf (1981). Results Annual means, standard deviations, standard errors, and coefficients of variation of Secchi disk transparency were calculated for each year in which Secchi disk transpar- ency data were available and are presented in Table 2. The highest valuesof Secchi disk transparency occurred in 1953 and 1954 (Table 2). The lowest Secchi disk transparencies occurredfrom 1973 through 1983. This period was affected by Bonnet Carrd spillway openings in 1973, 1 975, 1 979 and 1983. The greatest relative dispersion (coefficient of variation) was recorded in 1974 and 1978 during iheperiod TABLE 2 Statistics for annual Secchi disk transparency calculated from the original data set. Secchi disk transparency (cm) Year N* Mean High Low SD* SE* CV* 1953 62 131.69 431 30 76.36 9.70 59.4 1954 93 133,00 366 30 84.57 8.76 63.2 1969 71 89.31 183 15 39.51 4.69 44.2 1970 72 144.15 304.8 45.72 66.57 7.85 46.2 1971 37 140.87 182.9 91.44 23.88 3.93 17.0 1972 44 1 14.60 274 15.2 52.40 7.90 45.7 1973 208 79.29 274.3 9.1 41.59 2.88 52.4 1974 100 63.70 243.8 9.1 54.20 5.42 85.1 1978 219 60.60 165 1.5 37.42 2.53 61.7 1982 456 100.71 236.22 30.48 36.36 1.70 36.1 1983 685 55.79 182.88 2.54 30.54 1.17 54.7 1984 448 70.35 347.98 5.08 39.64 1.87 56.3 1985 35 106.80 213.4 14 47.70 8.06 44.7 1986 60 109.50 302.3 30.5 53.10 6.86 48.5 1987 59 68.00 142.24 25 26.00 3.38 38.2 1988 59 79.65 203.2 15.24 40.88 5.32 51.3 1989 59 102.00 182.88 30.48 34.00 4.43 33.3 1990 58 85.57 152.4 30.48 34.81 4.57 40.7 N = Number of Observations SD = Standard Deviation SE = Standard Error CV = Coefficient of Variation 4 Franqs et al. of spillway openings, allhough 1953 and 1954 also realized high relative dispersion. The lowest relative dispersion was recorded 1971. Average annual Secchi disk transparency is plotted as a function time m Figure 1 . The period of time represented in the graph is 38 years: 1953 through 1990. Specific years are indicated above each point in the graph. Linear regression analysis was performed on annual means. The slope of the regression line, -1.47 cm/year, is siaiislically significant; 0.01 < p < 0.02. The regression line indicates an apparent decrease in Secchi disk transparency from about 130 cm in 1953 and 1954 to about 80 cm in 1990 - an apparent decrease of about 40%. The data set is biased in that it docs not adequately represent the seasonal effects of salinity and wind speed, two variables dial have significant effects on Secchi disk transparency. Figure 2 shows the annual seasonality in salinity. It is a graph of average monthly salinity versus months of the year. The highest saliniiies occur in the fall (September, October and November) and the lowest salinities occur in the spring (April , May and June), Monthly means are based on 32 years of data from the STORET data base (U.S . Army Corps of Engineers). Thai data base was used to lest the validity of the apparent seasonality in salinity with analysis of variance. The ANOVA table for two-way analysis of variance without replication is pre.scnied in Table 3. The variance ratio, 21.18, exceeds the critical value for the test, 1.8, indicating that hi^y significant differences exist among monthly mean salinities, producing a highly signifi- cant annual seasonality in salinity. Figure 3 shows the annual seasonality in wind speed. It is a graph of average monthly wind speed versus months of the year. The highest wind .speeds occur in February and March and the lowest wind speeds occur in July and August. Monthly means are based on 38 years of data from the National Weather Service. That data base was used to test the validity of the apparent seasonality in wind speed with analysis of variance. The ANOVA table for two-way analysis of variance wiilioul replication is presented in Table 4. The variance ratio, 10X42, exceeds the critical value for the lest, 1.8, indicating that highly significant TIME (years) Figure 1. Annual mean Secchi disk transparency of Lake Ponlcharlrain from 1953 through 1990. SALINITY (ppL) Secchi Disk Transparency 5 TIME (months) Figure 2. Monthly mean salinity. TABLE 3 Analysis of variance of monthly mean salinity. Source SS df MS F* Month 333.77 11 30.34 21.28 Year 711.25 31 22.94 Error 484.79 340 1.43 Total 1529.81 38 F(0.95) = 1.8 WIND SPEED 6 Franqs et al. TIME (months) Figure 3. Moothly mean wind speed. TABLE 4 Analysis of variance of monthly mean wind speed. Source SS df MS F* Monih 825.50 11 75.05 103.42 Year 240.54 37 6.50 Error 295.34 407 0.73 Total 1361.38 455 F(0.95) = 1.8 Secchi Disk Transparency 7 SALINITY (ppt) Figure 4. Secchi disk transparency (individual points) versus salinity. differences exist among monthly mean wind speeds, pro- ducing ahighly significant annual seasonality in wind speed. Seasonal adjustment of the Secchi disk transparency data for salinity and wind speed was conducted in an effort to compensate for the seasonal bias in the data set. The adjustment for salinity is presented first. Secchi disk transparency is plotted as a function of salinity in Figure 4. siinity ilaare from the original data set. (Transparency values above 160 cm and salinity values above 10 ppt are not included in the graph.) Linear regression analysis was performed on individual points. The slope of the regression line, 8.13 cm/ppi salinity, is statistically significant; 0.01 < p < 0.02. Figure 5 is a graph of average annual Secchi disk transparency plotted as a function of salinity. Figure 6 is a graph of salinity versus lime the 38-year period 1953 through 1990. Salinity data are from the original data set. Although there is considerable year-to- year variation in salinity, there has been no long-term change in salinity. The slope of the linearregression line, -0.02 cm/year, is not statistically significant. The long- term average salinity, 3.9 ppt, was used as a base for seasonally adjusting the data for salinity. There are two equivalent ways to seasonally adjust the Secchi disk transparency data. One way is to adjust annual means where annual mean Secchi disk visibilities and amiual mean salinities are used in the calculation to provide adjusted annual mean Secchi disk visibilities. An equivalent procedure is to adjust individual points where individual Secchi disk transparency observations and associated salinities are used in (he calculation; adjusted annual mean Secchi disk visibilities arc then calculated from (he adjusted points. Indiv idual points are adjusted in the foUowmg example: The adjustment procedure employed the regression equation presented in Figure 5 of Secchi disk transpar- 8 Franqs et al. SALINITY (ppt) Figure 5. Annual mean Secchi disk transparency as a function of salinity. ency versus salinity: Y = 63.82 + 8.13X. Two values of Secchi transparency were calculated for each point: (1) Secchi disk transparency using the long-ienn average salin- ity, 3.9 ppl; (2) Secchi disk transparency using the salinity associated with the specific point. The difference between those two values was the adjustment factor for that point. The adjustment factor was subtracted from Secchi disk transparency for that point. This operation adjusts the data to the long-term average salinity. RguieT isa graph of annual mean Secchi disk transparency adjusted for salinity versus time. Comparison with Figure 1 reveals thal very little change in slope has occurred -- 1.47 cin/year to - 1 .34 cm/year. The relationship between Secchi disk transparency and time is still significant al the 5% level, indicating that on average the Secchi disk transpar- ency values in the original data set are not associated with unusually high or low salinities because of unequal rcpie- seniation of the seasonal effects of salinity in the data set. Figure 8 is a graph of Secchi disk transparency versus wind speed. The graph includes Secchi disk transparency points in the original data set. (Transparency values above 160 cm are not included in the graph.) Wind speed is the five-day average of mean wind speed. Data are from the National Weather Service data set. Linear regression was performed on individual points. The slope of the regres- sion line, -4,36 cm/mph, is siatisiicalJy significant; p < 0 . 01 . Figure 9 is a graph of average annual wind speed versus lime - the 38-year period from 1953 through 1990. Al- though there is considerable year-to-year variation in wind speed, there has not been a long-ienn ehange in wind speed. Regression analysis was performed on annual means. The slope of the linear regression line, -0.02 mph/year, is not statistically significant. The long-term average wind speed, 8.13 mph, was used as a base for seasonally adjusting the data for wind. Secchi Disk Transparency 9 Figure 6. Annual mean salinity of Lake Pontchartrain from 1953 through 1990. The adjustment procedure was the same as that de- scribed above for sahniiy. It employed the regression equation presented in Figure 7 of Secchi disk transparency versus wind speed: Y = 121.43 - 4.36X. Figure 10 is a graph of Secchi disk transparency adjusted for wind speed versus lime. Comparison with Figure 1 reveals that significant change in slope has oc- curred — L47 cm^ear to -1.06 cm/year. The relationship between Secchi disk transparency and time is no longer signiricaniaiihe5%levek0.05
0.5
Secchi Disk Transparency
11
selected because in 1953 Secchi disk transparency readings
were available only from August through December. It is
not surprising that Secchi disk transparency was high in
1953 whffli one considers that salinity is highest in October
and November (contributing lo high transparency values),
and that wind speed is lowest in August and September (also
contributing to high transparency values). Other years have
even higher average Secchi disk transparency values for the
August through December period. Annual means in Table
5 were calculated by taking the average of monthly means
ralher than an average of all data points. Regression of
annual Secchi disk transparency versus time produced the
following equation:
Y = 120.05 - 0.64X.
The slope, -0.64 cm/year, is not statistically significant,
p > 0 . 5 . On the basis of this analysis, it is concluded that
there has been no change in Secchi transparency over the
38-year period from 1953 through 1990,
Example 2. Table 6coniauis Secchi disk traasparency
values for those years in which conimuous data was avail-
able from January through June. This period was selected
because in 1954 Secchi disk transparency observations
were available only from January through June. The
seasonal bias in the original data set was removed by
constructing a data set consisting only of years in which
Secchi disk transparency observations were recorded from
January through June. Annual means in Table 6 were
calculated by taking the average of monthly means rather
than an average of all data points. Regression of annual
Secchi disk transparency versus time produced the follow-
ing linear regression equation:
Y = 75.13 -0.49X.
The slope, -0.49 cm/year, was not statistically significant,
p > 0,4. On the basis of this analysis, it is concluded that
there has been no change in Sccchi disk transparency over
the 37-year period from 1954 through 1990.
Example 3. The original Secchi disk transparency data
set, obtained by combining data from the soiirce.s indicated
in Table 1, is incomplete. Data arc missing for several
months in most years. Table 7 includes all years for which
there is at least some Secchi disk transparency data. Secchi
disk transparency was estimated for those months in which
data are noravailable - the so-callcd missing months in the
dataset.
Missing data points were estimated with the multiple
regression equation, Y = 97.83 + 8.03 X I - 5. 15 X2. and the
appropriate monthly average wind speed and monthly
average sahnlty. After estimating values for missing
months, annual inccUis for Secchi disk transparency were
calculated for 1953 through 1990. Regression of annual
TABLE 6
Secchi disk transparency for years in which data are
available - January through June,
Year
Time
(yr)
Transparency
(cm)
1954
2
97.46
1973
21
57.44
1974
22
4755
1978
26
38.04
1983
31
29.95
1984
32
47.97
1986
34
80.65
1987
35
57.49
1988
36
65.28
1989
37
87.27
1990
38
64.58
Regression transparency vs. lime; Y = 75.13 - 0.49X
P>0.4
TABLE 7
Secchi disk transparency with estimated values in
missing months.
Year
Time
(yr)
Transparency
(cm)
1953
1
94.89
1954
2
89.80
1969
17
87.13
1970
18
122.57
1971
19
101.54
1972
20
92.80
1973
21
75.37
1974
22
75.14
1978
26
59.12
1982
30
94.84
1983
31
43.86
1984
32
67.32
1985
33
91.71
1986
34
109.45
1987
35
67.48
1988
36
79.93
1989
37
102.23
1990
38
80.97
Regression transparency vs, lime:
Y = 95.52 - 0.42X
P>0.5
12
Francis et al.
WIND SPEED (mph)
Figure 8. Seech i disk transparencji (individual points) versus wind speed.
Secchi disk transparency versus time produced the follow-
LRg linear regression equation;
Y = 95.52 - 0.42X.
The slope, -0.42 ciWycar, is not statistically significant,
p > 0.5 . On the basis of this analysis, it is concluded that
there has been no change in Secchi transparency over the
38-year period from 1953 through 1990,
In summary, the historic data set on Secchi disk
transparency in Lake Pontchartnun is biased 'm that it does
not adequately represent the seasonal effects of salinity and
wind speed. When the seasonal bias is removed from the
data, it no longer supports the conclusion of a long-term
decrease in Secchi disk transparency.
Discussion
Regression of the origmal data on Secchi disk transpar-
ency versus lime (1953 through 1990) reveals a statistically
significant decrease in transparency with dme. The regres-
sion line suggests a decrease in transparency of about 40%.
However, the original data set is biased in that it does not
adequately represent the seasonal effects of salinity and
wind speed. Tlte data set was subjected to two analytical
procedures to determine the extern to which the apparent
long-tenn decrease in Secchi disk transparency was depen-
dent on the seasonal bias . One procedure involved seasonal
adjustment of the data for tlie effects of salinity and wind
sp^. Tlie olherprtKcdure was to remove the seasonal bias
by constructing unbiased data sets.
Secchi Disk Transparency
13
10.4
10.2
10.0
9.8
9.6
9.4
PL.
^ 9-2
9.0
P
W 8.8
H
a, 8.6
m
8.4
Q
^ 8.2
^ 8.0
7.8
7.6
7.4
7.2
7.0
TIME (years)
Figure 9. Annual mean wind speed for I.^ke Pontchartrain area from 1953 through 1990.
Regres.sion analysis revealed a statistically significant,
positive relationship between Secchi disk transparency and
salinity, and a siaiisiically sig nificani. negative relationship
between Secchi disk transparency and wind speed. Further
analysis indicated that neither average annual salinity nor
average annual wind speed had changed significanUy from
1953 through 1990.
Secchi disk transparency dam were seasonally adjusted
for the effects of salinity aiKl wind speed. The base for
adjustment in each case was the long-term average of the
variable for which adjustment was being made. Regression
of Secchi disk transparency (adjusted for salinity) versus
time revealed a statistically significant relationship, indi-
cating that the adjustment procedure had not influenced the
statistical significance of the long-term relationship be-
tween Secchi disk transparency and time. This result
indicates that on average the Secchi disk transparency
values in the original data set are not associated with
unusually high or low salinities because of unequal repre-
sentation of the seasonal effects of salinity in the biased data
set.
Regression of Sccchi disk transparency (adjusted for
w md speed) versus lime indicated that there was no longer
a statistically signincant relationship between Secchi disk
transparency and time; 0.05 < p < O.IO. Adjust'mg the data
for the effect of wind speed had reduced the level of
significance for the relationship from about 1% to about
10%. This result indicates that some Secchi disk transpar-
ency values in the original data set are associated with
unusually high or low wind speeds because of the unequal
representation of the seasonal effects of wind speed in the
biased data set.
Multiple regression of Secchi disk transparency (ad-
justed for both salinity and wind speed) versus time also
14
Francis et al.
Figure 10. Annual mean Secchidlsk transparency from 1953 through 1990 adjusted for wind speed.
indicated that there was no longer a siaiistically significant
relationship between Secchi disk transparency and time;
0.05 < p < 0. 10. Seasonal adjustment had reduced the level
of significance to about 10%. One can. therefore, con-
clude that some of the apparent decrease in Secchi disk
transparency in the original data is the result of unusually
high and low salinities and wind speeds realized because
of unequal representation of the seasonal effects of salinity
and wind speed in the biased data set.
Another analytical procedure undertaken with the
original data set was to remove the seasonal bias by
consuucting unbiased data sets. In most of the years
represented in the data set, data are not available for all 12
months of the year, especially before 1983. Only in the
late 1 980s arc daia consistently available for all 1 2 months
of the year.
Analysis of variance of monthly salinity data from
1953 through 1980, and 1986 through 1989 (32 years)
revealed a statistically significant annual seasonality,
with the highest values occurring in November and the
lowest values occurring in May. Similarly, analysis of
variance of monthly wind speed data from 1953 through
1990 (38 years) revealed a statistically significant annual
seasonality, with the highest values occurring in February
and the lowest values occurring in August. These seasonal
effects arc not adequately represented in the available data
on Secchi disk transparency in Lake Pontchartrain. The
seasonal bias was removed from the data by constructing
unbiased data sets in three ways: (1) The derived data set
contained Secchi disk transparency values for those years
in which continuous data were available from August
through December; (2) The derived data set contained
SEccm Disk Transparency
15
Figure 11. Anoual mean Secchi disk transparency from 1953 through 1990 adjusted for salinity and wind speed.
Secchi disk transparency values for those years in which
continuous data were available from January through
June; (3) The derived data set contained all of the original
data on Secchi disk transparency in addition to estimated
values for those months in which data was not available.
In each case, when the seasonal bias was removed from the
original data, it no longer supported the conclusion of a
statistically significant change in Secchi disk transpar-
ency from 1953 to 1990; p > 0.4.
Results of this study do not support the long-term
increase in turbidity of almost 50% reported by Stone
( 1 980). Although urban runoff is known to produce short-
term increases in water turbidity near outfall canals (Stem
and Stem, 1969), data examined in this study do not
indicate a long-ienn, lake-wide increase.
Acknowledgments
This project was funded by the University of New
Orleans Urban Waste Management and Research Center
under project number 92-B-003, Unpublished data used in
this study were provided by the Louisiana Department of
Environmcnial Quality and the U.S. Army Corps of Engineers.
16
Francis et al.
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Freeman, San Francisco. 859 pp.
Stcimlc and Associates, Inc. 1985. Shell Dredging Engineering
Report, Vol. 2, Exhibit 47, prepared for the Louisiana
Material Co., Inc.
Stern, D.H. and M.S. Stem. 1969. Physical, chemical, bacterial
and plankton dynamics of Lake Pontchartrain, Louisiana.
Technical Report No. 4, Louisiana Water Resources Re-
search Institute, pp. 3-4 and 12-18.
Stone, J.H. (ed.). 1980. Environmental Attalysis of Lake
Pontchartrain, Louisiana, Its Surrounding Wet-Lands,
and Selected Land Uses, Volumes 1 & 2. Louisiana State
University Center for Wetland Resources, Baton Rouge,
LA. Prepared for the U. S. Army Engineering District,
New Orleans. Contract No. DACW -29- 77-C-0253. 1219
pp.
Sutikus, R.D., R.M. Darnell and J.H. Darnell. 1954. Biological
study of Lake Pontchartrain. Annual report for the year, July
I, 1953 to June 30, 1954. Tulanc University, Zoology
Department, New Oilcans, Louisiana, pp. 36-44.
Swenson, E.M. 1980. General hydrography of the tidal passes of
Lake Pontchartrain. In: J. H. Stone (ed.), Environmental
Analysis of Lake Pontchartrain, Louisiana, It' sSurrounding
Wetlands and Selected Land U ses. Vol. 1 . Prepared for the
U. S. Army Engineering District, New Orleans, Contract
NO.DACW-29-77-C-0253. pp. 57-156,
Tarver, J.W. and J.B. Savoie. 1976. An inventory and study of
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Stale University, Baton Rouge, Louisiana.
Thompson, B.A. and J.S. Vcirct. 1980. Nekton of Lake
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Pontchartrain, Louisiana, Us Surrounding Wetlands and
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Gulf Research Reports
Volume 9 | Issue 1
January 1994
Namalycastis abiuma (Muller in Grube) 1 87 1, an Aberrant Nereidid Polychaete of a
Georgia Salt Marsh Area and its Faunal Associations
Erik Rasmussen
University of Copenhagen
DOI: 10.18785/grr.0901.02
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Recommended Citation
Rasmussen, E. 1994. Namalycastis ahiuma (Muller in Grube) 1871, an Aberrant Nereidid Polychaete of a Georgia Salt Marsh Area and
its Faunal Associations. Gulf Research Reports 9 (l): 17-28.
Retrieved from http:// aquila.usm.edu/gcr/vol9/iss 1/2
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Gulf Research Reports, Vol. 9. No. 1, 17-28, 1994
Manuscript leceived December 16, 1991; accepted October 18. 1993
NAMALYCASTIS ABIUMA (MULLER IN GRUBE) 1871,
AN ABERRANT NEREIDID POLYCHAETE OF A
GEORGIA SALT MARSH AREA AND ITS FAUNAL ASSOCIATIONS
ERIK RASMUSSEN
Zoological Museum, University of Copenhagen. UniversUetsparken 15.
DK-2100 Copenhagen, Denmark
ABSTRACT The moiphology of the aberrant ncreidid Namalycastis abiuma, Namanereidinae U described on the
basis of material collected 1 971-72 and 1976 in the brackish water drainage ditch system of Sapelo Island, Georgia,
USA, The syslcmatics of the species is briefly reviewed. The habitat and ecological conditions under which the
species lives in these brackish ditches are described.
At various times, M abiuma lives out of water under the bark of trunks and branches of fallen trees. Decaying
wood is ingested. It is suggested that future studies should concentrate on the reproductive biology of the widely-
spread, mainly tropical populations of what may prove to be not one, but several species of Namalycastis. A list
of the invertebrate fauna associated with N. abiuma is included with notes on these associates.
iNTRODUCnCW
Namalycastis abiuma (Namanereinae, Nereidae) was
described by Muller in Grube, 1 87 1 as Paranereis abiuma.
Eleven closcly-relaied species subsequently wcjnc described
under the generic name Lycasiis. These species occur in
ftesh water lo brackish or almost fully marine habitats
(Wesenberg-Lund, 1958). All species were referred to by
the new generic name Namalycastis by Hartman (1959),
with the comment that all “are believed to refer either to a
single species resembling the type, or to closely related, and
generically identical forms*' (p. 163). Hartman's diagnosis,
based on material from Florida, has been generally ac-
cepted (Foster, 1972; Gardiner, 1976; Gardiner and Wilson,
1977; Heard, 1975, 1982). Heard (1982) ^onymized
Lycastopsis Rioja, 1946,L.ponr/caJakubova,
1930, ami L. hummel incki Augener, 1933, all from North
Carolina, Georgia, Florida and Louisiana with N, abiuma,
N. abiuma was reported from Australia by Russell (1962)
and N. cf. abiuma by Hutchings and Glasby (1985), Al-
though it may seem difficult lo accept that Hartman rightly
synonymized 1 1 species of Abiuma^ considering the diver-
sity of their habitats, it must be noted that only a limited
number of systematic characteristics are available, e.g., a
pharynx without paragnaihs or papillae, reduced paiapodia,
elc. Therefore, until a more thorough revision of the many
forms is available, it seems reasonable to accept Hartman's
inclusion of them as members of Abiuma.
In this paper, the systematicsofN. ab/amn were briefly
reviewed and some morphological details were described
based on material from brackish water in Georgia. An
attempt has been made to characterize ecological condi-
tions under which the species occurred, its mode of life, and
its faunal associates.
Materials and Methods
Site Description
The study area encompassed shallow drainage ditches
on Sapelo Island connected to the sea only during periods
of extreme high water, A scries of ditches, dwindling into
pools at low water with different salinity conditions, were
chosen for sampling. Populations of M abiuma were found
at only two of 10 stations surveyed: Station 1, the main
station regularly examined during 1971-72, and Station 10,
a supplementary station visited only a few times in 1976
(Figure 1). Station I (Figure 2), situated one mile north of
the Settlement, was a roadside ditch about 4 m wide and
varying in depth from a few cm during dry periods to more
than 0.5 m at spring tides. The bottom layer was soft, fine,
blackish mud with some smell of hydrogen sulphide . Fallen
tree trunks and decaying branches from the siuiounding
pine forest were piled up in part of the ditch system.
Rickards (1968) gave a short description of this study area.
Except fora smallpatch ofRuppia maritima L., present
only in 1976, the ditches had no submerged vascular plants.
The surface of the mud was covered with adense brownish
layer of diatoms during periods with clear direct sunshine.
Tufts of perennial glasswon (Salicornia virginiana L.)
17
18
Rasmussen
Figure 1. Sapelo Island, Georgia, with tidal creeks, ditches and pools. Numbers indicate sampling stations.
were found on the bank of the ditch near the saltgrass cover {Spartina altern ijlora Lois.) occurred in some places along
{Disdchlis spicata (L.) Greene). Low bushes of marsh elder the bank edges and often extended across the ditch to form
(Iva frutescens L.) fonned a transitional border near the thresholds that often impeded the upstream flow of sea
forest in the Disdchlis marsh clearings. Saltmaish grass water.
Aberkant Nereidid Polychaete of Gh)rgia Salt Marsh
19
Figure 2. Pholograph showing part of Station 1, a roadside ditch with Spartina grass along the banks (to the right, opposite the
ro^). Behind the DistUhtis grass cover bushes of marsh elder {Iva frutescens) are bordering the pine tree forest in the
background (April 23, 1971).
Station 10 was a ditch located between steep bluffs
which ran parallel to (he road between the King Savannah
clearing and the Bell Maish near the High Point road. It was
surrounded by dense forest. The steep banks of the ditch
reached 2 m above the bottom. The bottom sediment was
virtually clean sand with plant remnants and scattered
Spartina. The banks were topped with a dense growth of
marsh elder. The ditch was nearly dry during sampling
periods. Direct access to sea water gave this di ich a regular
tidal cycle.
Salinity
Salinity was measured with a T/C re&actometer( Ameri-
can Optical Orp.). Salinity at Station 1 varied greatly
according to the irregular rainfall pattern. During most of
197 1 -72, the salinity varied from ca. lO%o to ca. 307(»» but
drought combined with high air temperature and intense
sunlight raised the salinity to 56 in June 1971. However,
heavy rains in June and July reduced that salinity to AVoo
within a few days.
In contrast. 1976 was an extraordinarily dry year. At
Station I from March 1 3 to April 1 6. total precipitation was
ca. 27 mm (seasonal noim 182 imn). The ditch became
almost dry in April, and the remaining stagnant pools
became hypersaline at ca. 807oo . But on April 12. a single
intrusion of sea water al a spring tide raised the water level
to 40 cm and lowered the salinity to thatof normal sea water.
It appears that fructuatioas in salinity over arange of ca. 2Ww
are a usual occurrence in spring and early summer. TheSfryoo
event rcpre.sents an extreme dial the fauna of the ditches
must endure occasionally, possibly by retreating to the
underbark refuge out of water. This may present other
stresses, such as high temperature and the risk of desicca-
tion.
Temperature
Temperatures were measured from April to August
1971 with a mercury thermometer. From late September
1971 to early February 1972, water temperature was mea-
sured each week with a permanently submersed maximum-
20
Rasmussen
minimum mercuiy thennomeier that showed the tempera-
ture rangeduringihcpastseveii days. From March 14-27»
the temperature range was measured continuously
with a Gram Miniature Temperature Recorder with
siK channels registering the air temperature, water
surface temperature in the middle of the ditch, water
surface temperature near the bank, temperature near
the bottom, temperature 1 cm in the mud bottom and
temperature 1 5 cm deep in the mud with a water level
ranging from 0.5 to about 40 cm (Figure 3). Rainfall
records for 1 97 1 -72 were ob lained from the meteoro-
logical station of the University of Georgia Marine
Institute. During the 1976 sampling, precipitation was
checked by a rain gauge placed on the ground close to
Station 1. Water level was measured daily against a
measuring rod placed in the ditch (Figure 2).
The temperaturerange at Station 1 was very large, both
seasonally and daily , influenced by changes in air lempera-
tuie and solar radiation. A fter a period of rhythmic fluctua-
tions in April and May 1971 varying between 22‘’C and
32'^C, the honest period in the 1971-72 study came in June
and lasted through September, with a peak of nearly 37'’C
in June. A more precise estimate of the temperauire range
was achieved with the introduction of regular maximum-
minimunv temperature recording of the ditch system water
from September 26 through the rest of the research period.
A minimum of O^C was recorded in January 1972,
From March 14-27, 1976, the water level of the pool
in Station 1 varied between 10 and 27 mm and the tempera-
ture ranged between 12®C and nearly 3 PC, never attain-
ing the low level of the air due to the strong solar radiation
(Figure 3). Whatmay be more important is the fact that the
narrower temperature range in the mud (15®C to 26.5° at
1 cmdeptli;20°to30°Cat 15 cm) might enable some mobile
animals to survive under extremeenvircHunenval conditions
by burrowing into the mud. However, such an escape may
subject themtoanoxicconditions.andM was never
actually found in the mud in this study.
Namalycastis abwma
Descriptive Notes
Mature specimens measure about 50 to 100 mm in
length, with up to 170 setigers. Body with two, not
distinctly separable sections. Anterior third to half rather
slender and cylindrical with relatively few segments, rest of
body becoming flattened posteriorly, with segments in-
creasingly shorter. Livingammalstranslucenkunpigmented.
Color determined by contents of red blood, increasing in
intensity posteriorly. Dorsal surface somewhat glossy in
reflected light. Epidennis of each segment witli fine
transverse wrinkles (Figure 4). Prostomium trapezoidal,
anteriorly incised, with short median groove. Two small
conical antennae and two conspicuous, broad palps with
distinct palposiylcs; the palps arc rhythmically extended
when the worm crawls. Posterior part of prostomium
broader with two pairs of eyes, black in reflected light, the
outer eye on each side larger (Figure 4). Four pairs of
tentacular cirri, the hindmost pair longest. First segment
achaetous. Pharynx strongly built, without paragnaihsorpf^-
SAPELO ISLAND DITCH SYSTEM NO. 1 TEMP RANGE MARCH 14.-27.1976
^C 5 10 15 20 25 30 35
I I I I •
AIR
SURFACE "j
NEAR BANK I WATER
NEAR BOTTOM J
1 CM IN ^
^ 15 CM IN J
I
BOTTOM
Figure 3. Temperature range in air and ditch at Station 1, Sapelo Island, Georgia, March 14-27, 1976. Measured continuously
during this period with a six-channel temperature recorder. All measurements, except "near bank", made over and In the
central and deepest part of the diteb. The “bank" channel was at the surface near the water edge. Depth during recording from
10 to 27 cm, falling to 9 cm.
Aberrant Nereidid Polychaeie of Georgia Salt Marsh
21
Figure 4. A^orfui/))<;as/uofriomu(MuUermGrube, 1871). Adult specimen from Station l,Sapelolsland, Georgia, November 1971,
showing anterior and posterior ends of Ibe body. Drawn IVom life with Ibe aid of a camera lucida.
lafi. with two dark biowiL Strong chidnous jaws (Figures). Jaws
ooncave,almosispoon-shaped, in living animals visible through
the first2-3setigers;median edge of eachjaw with arowof teeth.
The lenninal tooth, somewhat separated from the row of teeth,
slightly larger than the rest Each jaw with Fine growth rings.
Parapodia sub>biramoiis with noto* and neuiopodial aciculae.
dark brown or almost black, Notopodia normally reduced,
without setae except for an occasional, slender heterogomph
spiniger. Dorsal cirri anteriorly slender and small, conically
sh 2 y)ed; postcriody long, flattened leaflike in structure with
constricted terminal tips and a very' rich supply of fine c^illary
vessels. Ventral cirri small throughout.
Aberrant Nereidid Polychaete of Georgia Salt Marsh
23
Mature individuals wilh 11 to 21 neuroselae in each
fascicle; neurosctae of two types: hctciogomph falcigers,
numbering maximally 9 per fascicle, and heterogomph
spinigers with up to 12 per fascicle (Figure 5). Highest
number of each sctal type per fascicle found in the firs t third
of the body, declining in number posteriorly. Any bundle
of setae wiihdominanccof spinigers. Heterogomph falcigers
with blades finely denticulated, sometimes at base onJ y and
of varying lengths (Figure 5B-C). Heterogomph spinigers
with long, finel y den ticulate blade tapering into hair like tip.
Both falcigers and spinigers wilh dense structure of trans-
verse lamellae in cote of shafi, most distinct in falcigers.
The dorsal, longitudinal vessel has a slightly meandcr-
ing course in the first few segments, with meanders increas-
ing in amplitude considerably toward the posterior end
(Figure 4) (normally straight in ncieidids (Lindroth, 1938;
Nicoll, 1954). Ihecapillarysupplyisextracmhiiaiilyiichinche
dorsal part of theposterior segments and iniheleaflike, flattoied
dorsal cirri. Fresh dissection and sectioning of adult worms
from Sapelo Island has shown that each segment in the
worm body has pulsating “gill hearts” composed of two
contractile chambers (Figure Fcuertxrm (1931) has de-
scribed such hearts in Namalycastis ranaaensisi otherwise,
they arc rarely reported in nereidid wonns (Nicoll, 1954).
Biological Observations
N, abiuma was recorded from early November 1971 to
January 1972 and February-March 1976, with greatest
abundance in fall and winter. It was found under the bark
of rotten pine trunks and branches in or above the ditch
water. Heard (1982) also noted the presence of N. abiuma
in Mississippi living under nearly semi-terrestrial condi-
tions.
Except during the period from November 1971 to
March 1972. N. abiuma was not observed anywhere in the
ditches, not even the mud bottom. AH specimens recorded
had guts filled with wood pieces (Figures7-8) and the inside
of the surrounding bark had distinct marks made by the jaws
of the worms. N. abiuma lives freely under thebaik and has
no permanent tubes; the worms crawled away quickly when
bark was removed from the branches. In some cases, they
could live semi-terrestrially in the wood pieces since parts
of the branches protruded freely in the atmosphere. The
worm proved to be a very fast swimmer when released from
the wood. It seems likely that the wonns under the bark
were foraging, perhaps prior to reproduction. AH worms
taken in November were large, mature individuals with
smaU eggs in their segments. The spring specimens were
smaller and without sexual products.
Earlier accounts (Heard, 1982) have established that
N. abiuma is able to survive under very extreme environ-
mental conditions. At very low oxygen tensions, the
posterior end of the worm, wilh its foliaceous cirri rich in
capillary vessels, is seen extended from holes in the bark
and waving freely in the surrounding water (aquarium
observations. Sapelo Island). This was also observed by
Feuerbom (1931, p. 650) for Lycastis (Namalycastis)
ranauensis and personally lotbJereissuccinea from Sapelo
Island (see below).
Figure6. (Muller In Grube, 1971). Schematic diagram of the vascular system showing the main segmental
vessels. CIV, drcum-intesllnal vessel; DC, dorsal cirrus; DLV, dorsal longitudinal vessel; G, gut; GH, gill heart; VLV* ventral
longitudinal vessel; VNC, ventral nerve cord.
24
Rasmussen
Figure?. Namalycastisabiiuna, Sapelo Island, Georgia, November 1971, Station 1. Middle section ofadult, preserved specimen
with wood and bark pieces in the gut
Little is known about the reproduction and develop-
ment of N. abiuma. Only small egg cells were observed in
the coelom in the material froin Sapelo Island (November
197 1 ), and developmental details were not obtained. The
only more extensive breeding information for a member of
the Namalycastis group is given by Feuerbom (193 1 , Figure
10) ioxLycastis {Namalycasns) ranauensis from Java. He
found the species to be hermaphroditic with relatively small
eggs» 125-135 p in diameter and laid in a common jelly
mass. After about four days the larvae, about 300 p long,
hatched into what Feuerborn described and figured as a
ciliated neciochaete stage with three setigers and clearly
biramous parapodia. The subsequent fate of the larvae was
not described. Because of its freshwater habitat, it seems
Aberrant Nereidid Polychaete of Georgia Salt Marsh
25
I I—. i I
3mm
Figures, Namalycastis abiuma, Sapelo Island, Georgia, November 1971. Fecal pellets from adult specimen with remnants of
bark and wood particles.
very unlikely that N. abiuwa has a rrcc-swimmingpelagic stage.
Only Heard (1982), who kept individuals of N. abiurm in
aquaria, mentioned large eggs with direct devclopmeni as the
most likely form of propagation of the species, but gave no
further mformaiioa Otherwise, there are virtually no details of
file propagation of other Namafyatstis species.
Faunal Assodations
The survey below comprises benfliic species living associ-
ated with Namalycastis abiuma on or under the bark of dead and
windfallcn branches mostly of pine trees, predominantly the
loblolly pine, Pimis laeda L„ lying in the brackish waiter of
S^qielo Island ditches.
A indicates presence under bark and in wood
A indicates presence on surface of branches
POLYCHAETA
A Nereis (Neanthes) succinea (Frey and Leuckari, 1847).
Very common at all examined places, both in 1 971-72
and 1 976, Often large specimens; maximum length of
living animal 170 mm. It burrows under baik and
seems to feed on decaying wood. The animals were
surrounded by brownish excrement masses, undoubt-
edly originating from devoured wood remnants. Indi-
viduals from March 24, 1976 werealmost sexually ripe
and in the heteronereid stage. Under low oxygen
tensions combined with high water temperatures, the
posieriorend of the worm , with its many ligules rich in
capillary vessels, was seen e^ttended aiRl waving freely
in the water (laboratory observations). In case of
extreme low oxygen conditions, the species may leave
the water aiMi live partly amphibious under the bark of
branches exposed to the air.
26
Rasmussen
A Stettoninereis martini Wescnbcrg-Lund, 1958
This tiny aberrant nereid species is another remark-
able member of the decaying wood biotope of the tidal
ditches of Sapelo IslandL It was found both during
1971-72 and in March- April 1976, frequently in
groups of up to six individuaLs at a time and always in
grooves under the bark. AU specimens were taken
only in the spring in different parts of the ditches.
Living individuals measured 7- 12 mm. One ripe male
specimen was collected on April 16, 1976. The
morphology and systematic characters of the exam-
ined specimens agree with the description given by
Petdbone, 1971.
TTic species occurs mainly in tropical-subtropical
America. Since first described in 1958 by Wesenberg-
Lund from St. Martin in the West Indies, it has been
recorded from the eastern and northwestern parts of
the Gulf of Mexico and from North Carolina. It is
known from open water and tidal ponds with great
fluctuations in salinity (St. Marlin) and penetrates
into environments characterized by widely fluctuat-
ing conditions: warm mineral springs (Florida), salt
marshes (Texas and Mississippi)^ Spariina marsh
(North Carolina), and on silt and muddy substrate
with litUe or no oxygen (Hartman, 1958; Petlibone,
1971; Williams et al., 1976; Gardiner and Wilson,
1977; Heard, 1982).
^Poiydora fign/ Webster, 1879
Unee smaller specimens inmud tubesunderpine tiecbaik.
A Hobsonia florida (Hartman, 1951)
A single, ca. 12 mm long specimen in mud tube under
bark, BeU Marsh ditch system (Station 10), March 28,
1976, salinity 8. The systematic characters agree with
the description by Banse, 1979.
CRUSTACEA
A Balanus eburneus Gould, 1841
Fairly common, especially on the undersides of the
branches; maximum basic diameter 25 mm. Newly
settled individuals present on March 28, 1976 in the
Bell Marsh ditch system.
A Balanus improvisus Darwin, 1854
Common, predominantly on the sheltered sides of the
branches. On November 11, 1979, numerous small,
newly-seiilcd specimens present, less than 1 mm across.
On April 23, 1976, pelagic larvae in abundance at
Station 1.
A Hargeria rapax (Harger, 1879) = Leptochelia rapax
Harger, 1879
1 female with eggs, 3.5 mm long, under bark, Bell
Marsh diich system, March 28, 1976.
A Cyaihura polita Stimpson, 1855
Single specimen under bark. Bell Marsh ditch system,
March 28, 1976.
^A Cassidinidea ovalts (Say, 1818) = C. lunifrons
(Richardson, 1900)
In quantity under bark. From both Station 1 and the
Bell Marsh ditch system, where a few individuals were
observed crawling cm branches. Females with eggs,
March 28, 1976.
A Sphaeroma terebrans Bate, 1866 = S, destructor
Richardson, 1897
In quantity under bark and inship worm-bored branches
in all ditches examined.
^A Gammerus daiberi Bousfleld, 1969
Adult specimens numerous on and under the park of
pine branches, al.so in wood bored by shipworms,
salinity 87oq. Females with eggs, March 28, 1976.
This American endemic species is rather newly de-
scribed by Bousfleld (1969). IthasarestricteddLstribution
in estuarine systems from the Delaware and Chesapeake
Bay rcgKXis south to SouihCarolina AocordingtoBousfield,
the most dense populations arcatsalinitiesofl-57i» andin
mid-water to near bottom depths. It may be found at
15®Aw salinity, then largely pelagic: and devek^ent
within one year. Ovigenous females occur from March to
October. Its occmience on Sapelo Island seems to be the
most southern on recoid.
AA Melita nitida Smith, 1873
Adult specimens (both sexes) common under pine tree
bark at Station 1 , November 1971 and January 1972. In
March 1976 on and in rotten ranches.
A Uhlorchestia uhleri (Shoemaker, 1936)
Often in numbers, crawling on submerged parts of
branches close to the water surface.
A Panopeus herbsii H. Milne-Edwards, 1834
Two young females, carapace width 12 and 13 mm, in
empty shipwomi tubes.
A Euryiium limosum (Say, 1818)
Two males, carapace width 5.5 mm, under bark, Sta-
tion 1, January 20, 1972.
A Sesartna reticulatum (Say, 1817)
One female, carapace width 7 mm, under bark, Station
1, January 20, 1^2.
A Sesarma cinereum (Bose, 1801 or 1802)
Common under bark, carapace width 2.5 to 16nim,
Station 1, 1971-72 and 1976,
INSECTA
A Chironomkl larvae, blood-red species, a few *m mud tubes
under bark.
A Odonata, unidentified species, a single larva under bark;
November 11, 1971 at 20“/® salinity.
MOLLUSCA
A A Melampus bidenlam Say, 1822
A few small specimens under bark in water; also
observed crawling on submerged parts of the branches.
Aberrant Nereidid Polychaete of Georgia Salt Marsh
27
A Geukensia demissa (DiUwyn, 1817) = Modiolus
demissus (JDillyfyn, 1817)
A few byssally^attached specimens under bark, length
about 1 5 nun,
A Crassoslrea virginica (Gmelin, 1791)
Common on branch surfaces, maximum size 80 mm,
many dead sheUs.
A Bankia gouldi Bartsch, 1908
Fairly common, often in small and thin branch pieces.
A Teredo bartschi Clapp, 1923
Fairly common, often in small and thin branch pieces.
ENTOPROCTA
^ Barentsia sp.
Not very common, on surface of bark in various ditch
systems.
ECTOPROCTA
Living colonies of the following species were found in
abundance on the surfaces of branches, attached barnacles
and oysters,
A Membranipora tenuis Desor, 1848
A Electro monostachys (Busk, 1854)
A Conopeutn temissimum (Canu, 1928)
A Bowerbankia gracilis O’Donoghue, 1926
A Alcyonidium polyoum (Hassall, 1841)
A Victorella sp.
ASCIDIACEA
A Molgula manhattensis (De Kay, 1843)
Present, but uncommon, as large specimens on the
outer surface of branch pieces.
ACTINURIA
A Even one tiny unidendfied flesh-colored sea anemone
was taken under loose pine bark below sea water.
Discussion
In considering the taxonomic status of Abimm, even
generally established systematic characters must be used with
care. For example, the position of theeyes of /V. abiuma may be
differeiUaccx)ixlingtothecofidiUonoft]iejHeservcdiTiaisrial. In
the Sapelo Island material, living woims had the eyes in a
transverse row (Hgure4), while they were behind each other in
preserved and somewhat shrunken ^)ecimcns.
An aid in species scpaiaiion within the genus Atortfl/ycas/«
may be offered by possible differences in i nodes of propagation
and developinenL Hartman (1959, p. 163) mendmis one form
of the type species (Paranereis (Namalycastis) abiuma Muller
in Giube, 1871) from Brazil, which was described as having
small eggs and separated sexes, with no mention of fimher
development. Another form {N. ranauensis) widi small eggs.
hennaphioditism,andafux:tochaetestago(pcihapspelagic)was
described by Feueiboni( 1931). Both forms wereftom freshwa-
ter. The results of Heard (1982) indicaie large eggs and diiea
developmcnl for what he consideis to be the type species N.
abiuma from brackish water. Still rather incomplete, these
descriptions, apparently with the same external characters, may
suggest llueediffereruspedesatany rate. Furihersludiesonthe
bteedingbiology of this aberrant group may providcaclue to the
^xsciaiion problems within the genus Namalycastis.
The ingestion of decaying and rotten wood seems to be
unknown for nereidids and pediaps for polychaete worms as a
whole (Fauchald and Jumars, 1979). Not only Namalycastis
has this peculiar feeding patterns, hulNereislNeanihes)
suednea also consumes decaying wood, as shown in this study.
It seems reasonable to assumeihat the fractionof importance for
the two species is the microargarusnis of the wood.
Off ttre German coast, N. succinea is a deposil-feeder and
detritus-feeder(Goerke, 1971). N.ab/u/Twinayalsobeadeposil-
feederinotherparisofiisrangeofdistnbution. Thus their diets
may vary greatly and both may be characterized as omnivoies.
However, aspobiled ouvby Fauchaldand Jumars ( 1979, p. 255),
widely dLspersed species feeds on a limited range of
inatcrials, indicting that, while the species as a whole may be
omnivoroiis, eachpopulation may be functionally specialized.”
The ifouna associated with N. abiuma in or on fallen
branches in the ditch watercompriscs 34 benthic species. Apart
from the two freshwater insects, the remaining arc brackish-
waier.estuarineoreuryhaline marine species. There is a clear
dominance of crustaceans with 13 species, followed by five
polychaetes, five molluscs, and six ectoprocts (bryozoans).
Acknowledgments
Special thanks arc expressed to Professor V.J. Henry,
former director of the University of Georgia Marine
Institute, for arranging my visit in 1971-72 as a staff
member at the station. Thanks are also extended to all
personnel for their kind help and assistance during my
visits. I am indebted to Professor W.D. Burbanck and the
late Professor Ralph 1. Smith for helpful comments in
reviewing the manuscript, and to Professor C. Overgaard
Nielsen for correcting and revLsmg the manuscript. I am
indebted to the following experts for their aid in the
identification work: Dr. J. Just, Zoological Museum,
Copenhagen; Dr. R. Turner, Museum of Comparative
Zoology, Harvard University; Dr. K.B. Hansen, Zoologi-
cal Museum. Copenhagen: and Dr. Pairicia Kotl,
Queensland Museum, Australia. Lastly, I would like to
acknowledge financial support provided by the Danish
Natural Science Research Council and the Carlsberg
Foundation.
The material collected is deposited in the Zoological
Museum, Copenhagen.
28
Rasmussen
Lf 1' 1 ilRA'ITJRE OrTED
Bous field, E.L. 1969. New records of Gammarus
(CrustaccaiAmphipoda) from ihc Middle Atlantic Region.
ChesQpeak£ Sci. 10.1-17.
Fauchald,K.andP,A. Jumars. 1979. Thcdietofwoims: a study
of polychaete feeding guilds, Oceanogr, Mar. Biol. Ann.
Rev. 17:193-254.
Feuerbom, HJ. 1931. Ein Rhizocephale und zwei Polychacten
aus dem SUsswaascr von Java und Sumatra. Verh. Jm.
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DC. pp. 1-15.
Gardiner, S.L. 1976(1975). Errant polychactc annelids
from North Carolina. J. Elisha Mitchell Sci. Soc.
91(3);77-220.
Gardiner. S.L. and W.H. Wilson. 1979(1977). New records of
polychactc annelids from North Carolina with the descrip-
tion of a new species of Sphaerosyll'is (Syllidac). J. Elisha
Mitchell Sci. Soc. 93(4): 159-172.
Goerkc, H. 1971. Die &nJilirungsweisc dcr Nereis-AiiXsn.
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Meeresforsch. Bremerh. 13:1-50.
Grube, E. 1871. tJber die Gattung Lycaslis und cin Paar ncuc
Arten derselbcn. Jahresber. Schles.Gesetls. Vaterl.Kultur,
Breslau 49:47-48.
Hartman, O. 1958. A new ncreid worm from warm mineral
springs, Ra., with a review of the genus Nicon Kinberg, J,
Wash, Acad. Sci. 48:263-266.
, 1959, Capitellidac and Ncrcidae (marine annelids)
from the Gulf side of Horida, with a review of freshwater
Neieidac. Bull. Mar. Sci. GuJfCaribb. 9(2): 153-168.
Heard, R.W. 1975. Feeding habits of white catfish from a
Georgia estuary, Biol. Sci. 38(l):20-28.
. 1982. Guide to Common Tidal Marsh Invertebrates of
l he Northeastern Gulf of Mexico. Missi ssippi- Alabam a Sea
Grant Consortium, pp. 1-82.
Hutchings, P.A. and C.J. Glasby. 1985. Additional mcreidids
(Polychacla) from eastern Australia, together with a rede-
scription of Namanereis quadraticeps (Gay) and the
synonymising of Ceratonereis pseudoerythraeensis
Hutchings and Turvey with C. aequiset 'ts (Augener). Rec.
Austr. Miir.37(2):101-110.
Lindroth, A. 1938. Studien liber die rcspiratorischenMechanismcn
von Nereis virens Sars. loot. Bidr. Upps. 17:367-497.
NicoU.P.A. 1954, Theanalomyandbehaviourofdievascularsystenis
in Nereis virens and Nereis limbaia. Biol. Bull. 106:69-82.
Pettibone, M.H. 1971. Revision of some spuncs referred to
Leptonereis,Nicon^m(iLaeonereis(Po[ych^la:Nerci6id3£).
Smithson. Contr.Zool. 104:1-53.
Rickards, W.L. 1968. Ecology and growth of juvenile tarpon
Megalops atlaruicus in a Georgia saltmarsh. Bull, Mar. Sci.
18(l);220-239.
Russell, B. 1962. Some nereid polychaetes from Queensland.
Papers Department of Zoology, University of Queensland
2(1):M2.
Wesenberg-Lund.E. 1958. Lesser Antillean polychaetes, chiefly
from hrackish-watcr, with a survey and a bibliography of
fresh and brackish- water polychaetes. St ltd, Famaof Curasao
and Other Caribbean Islands 8:1-41.
Williams, G.E. in e/ o/. 1976. WeatemGulf of Mexico records
of 5renoni/terefr/nar/ini Wesenberg-Lund 1958 (Polychaeta,
Ncrcidae) with contributions to its habitat ecology. Contr.
Mar. Sci, 20:83-85.
Gulf Research Reports
Volume 9 | Issue 1
January 1994
A New Species and Two Known Species of Free-Living Marine Nematodes (Nematoda:
Monoposthiidae) from Northwest Florida^ U.S.A.
Edwin J. Keppner
DOI: 10.18785/grr.0901.03
Follow this and additional works at: http:/ / aquila.usm.edu/ gcr
Part of the Marine Biology Commons
Recommended Citation
Keppner, E. J. 1994. A New Species and Two Known Species of Free-Living Marine Nematodes (Nematoda: Monoposthiidae) from
Northwest Florida, U.S.A.. Gulf Research Reports 9 (l): 29-38.
Retrieved from http://aquila.usm.edu/gcr /vol9/issl/3
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Guif Research Reports,\ol 9, No. 1, 29^38, 1994
Manuscript received March 19, 1993; accepted June 1, 1993
A NEW SPECIES AND TWO KNOWN SPECIES OF FREE-LIVING
MARINE NEMATODES (NEMATODA; MONOPOSTHIIDAE)
FROM NORTHWEST FLORIDA, U.S.A.
EDWIN J.KEPPNER
4406 Garrison Hoad, Panama City, Florida 32404
ABSTRACr Two known free-living marine nematodes, Monopost hioides mayri Wicser and Hopper, 1967 and
Monoposlhia hexalata Chitwood, 1936 arc redescribed from sediments in St. Andrew Bay and Lake Powell, Bay
County, Florida, U.S. A, One new species of free-living marine nematode, Monoposthia baxterin. sp., is described
from nonvegetated sediments in St Andrew Bay, Bay County, Florida. Af. baxteri n. sp. differs from the other
members of the genus in the shape of the gubemaculum which is more similar to that of the species of
Monopost hioides than that of Monoposthia.
Introduction
According lo Lorenzen (1981), the family
Monoposthiidae Filipjev, 1934 contains the genera
Monoposthia de Man, 1889; Monoposthioides Hopper,
xmiNudora Cobh, 1920, m6Rhinema Cobb, 1920. Tlie
Monoposthiidae are characterized by the presence of a
cuticle w ith strong transverse striations forming annuli, and
a number of longitudinal cuticular ridges that appear as
V-shaped markings. Vanreusel and Vincx (1989) referred
to these structures as costae. The amphids are circular and
are situated on the second annulus. The buccal cavity has
a well-developed dorsal tooth and may have one or more
ventral teeth or denticles.
Specimens of two of the four genera of the
Monoposthiidae were collected from estuarine waters in
northwest Florida. The two known and one new species of
frec-h ving marine nematodes in the gGnemMonoposthioides
Hopper, 1963 and Monoposthia de Man, 1889 redescribed
and described, respectively, herein were collected from
subtidal sediments in St. Andrew Bay and Lake PowcD, Bay
County, Florida. The sediments from the collection sites in
St. Andrew Bay and Lake Powell were nonvegetated fine
sand and silt.
Materials and Methods
Sediment samples were obtained with a cylindrical
core sampler lo a depth of 4- 10 cm, depending on the site.
Nematodes were extracted from the sediment by repeated
decantation. The suspended material from four washings
was allowed to settle forl5-20minutes,and the supernatant
water was decanted. Nematodes were removed alive from
the settled material and fixed in hot alcohol-formalin-acetic
acid or hot 4% formalin in seawater for 24 hours. Speci-
mens were dehydrated 'm glycerine by gradually bringing
them 10 70% ethyl alcohol and glycerine (9: 1) and allowing
the alcohol to evaporate. Specimens were mounted in
anhydrous glycerine on Cobb slides. Specimens were
deposited in the Florida Nematode Collection, University
of Florida, Gainesville, Florida (UFNC).
All measurements are given in pm unless otherwise
staled , and the mean is followed by the range in parentheses.
Abbreviations; 1 = length of body in nun. w = width at
midbody, hd = head diameter at level of first annulus, cs
= length of cephalic sensilla. ad = width of amphid. aa=
anterior end to anterior margin of amphid. be = length of
buccal cavity, nr = anterior end lo nerve ring, es = length
of esophagus. i = length of tail, cw = width at cloaca, aw
s: width at anus. av=: anterior lo vulva. a,b,c,V=demanian
ratios.
Taxonomic Account
(After Lorenzen, 1981)
Chromadorida FUipjev, 1929
Monoposthiidae Filipjev, 1934
Monoposthioides Hopper, 1963
Monoposthioides $nayri Wieser and Hopper, 1967
Figures 1-12
Description: Body relatively short, broad. Cuticle
coarsely aimulated; annuli originate immediately posterior
to cephalic sensilla; first and second annuli larger than
succeeding annuli. Annuli are complete lateral to cloaca.
29
30
KHTNOt
Costae in 12 longitudinal rows; fully developed V-shaped
costae originate between annuls 10and20frDfn anterioroid
[(38.5(30-56) in males; 60(50-77) in females). Apex of
costae directed posleriorly then reverse to anterior duection
234.7(218-256) from antedor end in males, 3 19.7(301-346)
in females. In males, lateral, subvential, and ventral rows
of costae termifiate at level of clocal opening; remaining
rows terminate immediately posterior to cloacal opening.
In females, suhventral and ventral tows of costae tenninate
at level of vulva; remaining rows terminate posterior to anal
opening. Head withcircleof six, $mall,iimerlabialsensiUa
immediately adjacent to oral opening. Circle of six
papilliform outer labial sensill and four long, setiform
ce{Mic sensilla present. Long cervical, somatic, and
caudal scnsilla present as subdorsal andsubvcncral rows on
each lateral suri^ace. Amphid circular, situated on second
annulus. Buccal cavity with cyathifoim anterior chamber
with circle of 12 small, flap-like structures. Anterior
cliainber of buccal cavity elongate with culicularized,
parallel walls. Esophagus with asymmetrical peribuccal
expansion; dorsal side larger. Large, muscular, bipartite,
posterior, esophageal bulb present with moderately
cuticuiarized lumen. Excretory pore not observed. Tail
conical, terminal one third without annuli; spinneret and
caudal glands present.
Males (a = 6); 1 = 1.15(1.01-1,28). w =40.1(38-43).
hd= 16(14-17). cs = 22(21-24). ad = 2.8(2.5-3.n). aa =
13.8(13-16). be = 23.7(19-27). nr=68(61-75). es= 144.2
(125-155), 1 = 99.8(93406). cw = 31<29-34>. a = 28.6
(26.6-31.6). b = 7.98(7.23-8.53). c = 12,1(10.6-15.3).
Male reproductive system diorehic. Large, non-striated,
precloat^piocesspresenL SpiculesabsenL Single, heavily
cuticuiarized gubemaculum present. 46.6(45-48)arc.51(48-
56) chord long, arcuate with proximal flange, dorsally
directed process of flange longer than ventmlly directed
process.
Females (n =3): 1=1,15(1.11-1.20). w = 50(48-51).
hd= 16.7(16-18). cs= 19.7(19-21). ad = 4.0(3.0-5.0). aa
= 13.3(1344), be = 25.3(22-27). nr = 78(72-82). e5 =
157(144-173). t = 94(90-101). aw = 25.7(24-27). av =
979(949-1020). a =22.9(2 1.8-23.5). b= 7.33(6.94-7.85).
c= 12,2(11.9-12,6). V=85.3%(85-86). Female reproduc-
tive system monodelphic, prodelphic, ovary reflexed. Vulva
with cuticular flap.
Specimens: Males. UFNC A157. A158, A159; fe-
males, TJFNC A160.
Locality: St. Andrew Bay, Bay County, Rorida
(SODS’SS^N, 85'*42M3''W). Nonvegetated fine sand and
sill.
Remarks; The specimens described above arc consid-
ered to be Monopoithioides mayri based on the shape and
size of the gubernaculum of the male, Ihe enlarged second
annulus, and the shape and size of the amphid. In the
original description of M. mayri, the buccal cavity was
described as having a single, large, dorsal tooth and small
subventrsl projections. These projections are part of three
circles of small denticles that are not easily observed. The
presence of inner labial sensilla was not mentioned in the
original description or figured on the drawings. The male
specimens described above differ from the original descrip-
tiem of the male in that the costae reverse at a greater
distance from the anteriorend [234.7(218-256) vs. 140] and
the cephalic sensilla are longer [22(21-24) vs. 17]. The
female specimens described above differ from the original
description of the females of M. mayri in that the “V” value
is less than that of M mayri (85-86% vs. 9ft;92%) and the
costaereverse somewhat mote posteriorly than inM. mayri
(301-346 vs. 240-250 from the anterior end).
Monopostkia de Man, 1889
Monopostbia baxteri n. sp.
Figures 13-21
Description; Body relatively short, broad, (^ticlc
coarsely annulated; second annulus with anterior bulge at
location of amphid. Annuli incomplete subventrally and
ventrally in cloacal region of male. Costae in eight longi-
tudinal rows; dorsal, subdorsal, suhventral, and ventral
rows originate on tliird annulus, lateral rows originate on
annulus 13-15. Apex ofoostne directed postcrioily. reverse
direction on annulus 83-88 from amerior end (posterior to
esophageal bulb) in males; costae did not reverse in single
female examined. In males, laterals, subvenirals, and
ventral rows of costae tenninate at about level of cloacal
opening; subdorsals and dorsal rows of costae terminate
posterior tocloacal opening, frifemale.laterals, subvemrals.
and ventral rows of costae tenninate at vulva; subdorsals
and dorsal rows terminate immediately posterior to anal
opening. Head with circle of six. setifoim. inner labial
sensillaimmediately adjacent to oral opening. Circleof six,
setiform, outer labial sensilla and circle of four, long,
sedfonn cephalic sensilla present Amphid circular; situ-
atedon second annulus. Long cervical, somatic, and caudal
setifoim sensilla present as suhventral and subdorsal rows
on each lateral surface. Buccal cavity with anterior
cyatfiifonn chamber with 12 Qap-like structures. Large,
heavily cuticuiarized, dorsal tooth and three circles of
denticles present. Circles of denticles broken subdorsally
and dorsally. Posterior chamber of buccal cavity elongate
with cuticuiarized, parallel walls. Peribuccal region of
esophagus expanded, asymmetrical; dorsal side larger.
Large, muscular, bipartite, esophageal bulb with we^y
cuiicularizcdlumenprescntposieriorly. Excretory pore not
observed. Tail conical, terminal one third without annuli;
Spinneret and caudal glands present.
Males (n =2); 1=1.05(1.04-1.06). w=56(54-58). hd
= 22(22-22). cs = 26.5(26-27). ad = 3.0(3.0-3.0}. aa =
New and Known Species of Marine Nematodes
31
10(10-10). be = 30.5(29-32). nr = 81(80-82). es =
157.5(155-160). cw = 36(35-37). l = 55(54-56), a =
18.8(18.3-19.3). b= 6.67(6.50-6.84). c = 11.6(11.4-11.8).
Reproductive system diorchic. Non-slriated. precloacal
process present. Spicules absent GubemacuJum large,
55(54-56) arc, 60(59-6 1) chord Iong,arcuaie, thorn-shaped
with inner cuticularization. Distal end expanded with
ventral process longer than dorsal process. Small teeth
present on ventral surface of proximal tip of gubemaculnm
in paratype male, not observed in holoiype male. Cuticle
inflated in one place on midventral surface anterior to
cloaca.
Female (n = 1): 1= 1.02. w = 51. hd= 18. cs = 21.
ad = 4. aa=ll. be = 29. nr =77. es=144. aw = 27. t =
83. av = 914. a = 20.0. b = 7.08. c = 12.3. V == 90%.
Reproductive system monodelphic, prodelphic, ovary re-
flexed. Vulva with cuticular flap.
Specimens: Male, holotype, UFNC A166; male,
paratype, UFNC A168; female, allotype, UFNC A167.
Locality: St. Andrew Bay, Bay County, Florida
(3(>f)833"N, 85'^42’43"W). Nonvegeiatcd fine sand and
silt.
Remarks: Hopper (1963) erected the genus
Monoposthioides to accommodate the species
Monoposthioides anonoposthia Hopper, 1963 that was
collected from the northern coast of the Gulf of Mexico.
The genus Monoposthioides can be differentiated from the
genera Nudora, Rhinema and Monoposthia in that the
costae originate about midlevel of esophagus in
Monoposhtioides rather than on the second or third annulus
as in the other Uiree genera. In addition, Monoposthioides
differs from Nudora and Rhinema hi in the absence of
spicules.
Monoposthioides is most similar to the genus
Monoposthia in that the spicules are absent and a single
well-developed gubemaculum is present. Hopper (1963)
differenliaied Monoposthioides from Monoposthia on the
basis that the costae originate much more posteriorly in
Monoposthioides^ the gubemaculum of the male in
Monoposthioides is relatively larger and more arcuate with
a large, ventrally directed process proximally and long
spine distally, and the reproductive system of the male in
Monoposthioides is diorchic. Wieser and Hopper (1967)
emended the diagnosis of Monoposthioides to include the
species Monoposthioides mayri Wie-ser and Hopper, 1967.
In M. mayri, the long, distal spine of the gubemaculum is
absent and the dorsal process of the proximal end of the
gubemaculum is longer than the vcnual process.
The diorchic male reproductive system cannot be used
as a differentiating character of Monoposthiodes, because
diorchic males of known species of Monoposthia have been
described by Kilo (1981 ) and Vanreusel and Vincx ( 1 989).
Plait and Warwick (1988) use the diorchic condition of the
male reproductive system as a character of the family
Monoposthikiae. Therefore, the genus Monoposthioides
currently differs from Monoposthia in that the costae
originate more posteriorly, and the gubemaculum is rela-
tively larger and more arcuate in Monoposthioides.
Monoposthia haxteri n. sp. has characters of both
Monoposthia and Monoposthioides. It is similar to
Monoposthia in that (he costae begin on the third annulus
and to Monoposthioides in that the gubemaculum is rela-
tively large, arcuate, and the proximal end has a large
ventral process. Monoposthia baxteri n.sp. is placed in the
gtnus Monoposthia based on the origin of the costae on the
third annulus.
Monoposthia baxteri n. sp. is differentiated from all
other members of the genus Monoposthia on the basis of the
shape of the gubemaculum. It is the only species with a
large, arcuate gubemaculum with an expanded proximal
end with the ventral proce.s.s longer than the dorsal proces.s.
Etymology: Monoposthia baxteri n. sp. is named for
Dr. George Baxter, Professor Emeritus, University of
Wyoming, in recognition of his work and teaching in
aquatic biology.
Monoposthia hexataia ChitwoodT 1936
Figures 22-29
Descriprion; Body relatively short, broad. Cuticle
coarsely annululated. Second annulus not significantly
larger than succeeding annuli but with an anterior bulge
where the amphid i.s located. Annuli complete laterally and
ventrally in cloacal region of male, but these annuli are not
as distinct as the surrounding annuli. Costae in six longitu-
dinal rows; originate on third amiulus. Apex of costae
directed posteriorly, reverse direction immediately poste-
rior to esophageal bulb in males, immediately anterior to
vulva in females. In males, subventral and ventral rows of
costae terminate immediately anterior to cloaca; remaining
rows terminate posterior to cloaca. In females, subventral
and ventral rows of costae lertninatc immediately anterior
to vulva; remaining rows terminate at or near last annulus
on tail. Head with circle of six seiifonn inner labial sensilla
immediately adjacent to oral opening . Circle of six setiform
outer labial sensilla and four long, setiform, cephalic sen-
silla present. Amphid circular, situated on second annulus.
Cervical, somatic, and caudal setiform sensilla present as
subdorsal and subventral rows on each lateral surface.
Buccal cavity with anterior cyathiform chamber with 12
flap-like structures. Anterior chamberof buccal cavity with
single, large, heavily cuticularized dorsal tooth and pair of
small, subventral, denticles; circles of denticles not ob-
served. Posterior chamber of buccal cavity elongate with
cuticularized. parallel walls. Peribuccal region of esopha-
gus expanded, asymmetrical; dorsal side larger. Large,
muscular, bipartite, esophageal bulb with weakly
32
Keppner
cuticulaiized lumen present posteriorly. Excretory pore not
observed. Tail conical; leiminal one third without annuli;
spinneret and caudal glands present,
Malea(n=5); 1=0.963(0.831-1,06), w= 48.4(43-53).
hd= 18.6(17-19). cs = 24,8(22-26). ad = 3. 1(3 .0-3.2). aa
= 7.4(7-10). be = 25.6(22-29). nr = 77,6(67-86). cs =
148,8(133-165). cw = 36.6(2443). 1 = 92.2(80-99). a =
20.0(15.7-22.1). b = 6.47(6.1 1-6.82). c= 10.6(8.4-13.0).
Reproductive system diorchic. Spicules absent.
Gubemaculum claw-shaped 392(34-43) arc, 42.4(36-47)
chord long, with proximal expansion with dorsally directed
process, internal cuticularizalion, and arcuate distal part.
Single large, subvcntral, papillifoim, precloacal sensiilum
presenton each lateral surface. Cuticle inflated midventially
in two places anterior to cloaca, particularly evident when
tail is bent ventrally.
Female (n = 1): 1 = 0.945. w = 67. hd = 22. cs=19.
ad = 5. aa = 1 1. be = 29. nr = 80. es = 174. aw = 26. t =
82. av = 788. a =14.1, b = 5.43. c=ll.5. V = 83%.
Reproductive system monodelphic, prodelphic, ovary re-
flexed. Vulva with cuticulariz^ flap.
Specimens: Males, UFNC A 16 1 , A162, A 163, A 164;
one female, UFNC A 165,
Locality: St. Andrew Bay, Bay County, Florida
(3(K)8’3 3‘'N, 8542*43 "W) and Lake PoweU, Bay County,
Florida (30^16*45"N* 85^* 58’50"W). Nonvegetated fine
sand and silt.
Remarks: The specimens described above agree closely
with the descriptiem and drawings of M. hexalata provided
in the original description given by Chitwood (1936). They
differ from the original description in that there is a pair of
precloacal papillae in the males that were not mentione.
Vanreusel,A.andM. Vincx. 1989. Free-living marine nematodes
from the Southern Bight ofthe North Sea. IQ. Species of the
Monoposthiidae Filipjev, 1934. Cah.Biol. Mar. 30:69-83.
Wieser, W. and B.E, Hoiq)er. 1967. Marine nematodes of the
East Coast of North America. I. Florida, Bull. Mas. Comp.
Zool. Harv. 135:239-344.
Gulf Research Reports
Volume 9 | Issue 1
January 1994
Behavioral Ecology of Two Teal Species (Blue-Winged Tesl^Anas discors, and Green-
Winged Teal; Anas crecca) Overwintering in Marshes of Coastal Louisiana; USA
Gary R. Gaston
University of Mississippi
Jeanne G. Nasci
DOI: 10.18785/grr.0901.04
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Part of the Marine Biology Commons
Recommended Citation
Gaston, G. R. and J. C. Nasci. 1994. Behavioral Ecology of Two Teal Species (Blue Winged Teal, Anas discors, and Green Winged Teal,
Anas crecca) Overwintering in Marshes of Coastal Louisiana, USA. Gulf Research Reports 9 (l): 39-48.
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Gulf Research Reports, Vol. 9, No. 1, 39-48, 1994
Manuscript received July 21, 1993; accq>ied October 20, 1993
BEHAVIORAL ECOLOGY OF TWO TEAL SPECIES (BLUE- WINGED
TEAL, ANAS DISCORS, AND GREEN-WINGED TEAL, ANAS CRECCA)
OVERWINTERING IN MARSHES OF COASTAL LOUISIANA, USA
GARY R. GASTON' AND JEANNE C. NASCP
‘Department of Biology, University of Mississippi, University, Mississippi 38677
^3186 Worthington Avenue. Fort Collins, Colorado 80526
ABSTRACT Feeding and other dominant activities of Blue- winged Teal (BWT; Anas discors) and Green-winged
Teal (GWT; Anas crecca) were compared from October 1987 to March 1988 in southwestern Louisiana, USA.
Three observation towers were constructed near similar inlermediale marsh habitats in areas where BWT and GWT
concentrated for feeding. These observation towers allowed activities of the two species to be compared throughout
the nonbreeding season. Although BWT and GWT often fed together, time spent in various activities differed.
Feeding was the most frequent activity of both BWT (64.5%) and GWT (55.3%), but BWT spent more time feeding
(P < 0.01) and alert (P < 0.05), but spent less (P < 0.01) time resting than GWT. Within each species there were
differences in activity budgets among daily time blocks and among months, but few differences among the three
habitats studied. Temperature and light intensity were correlated with resting (+), feeding (-), locomotion (-), and
preening (+). Daily and monthly activity budgets of BWT and GWT were similar, as were ingested foods,
suggesting that these two species used the study areas primarily for foraging, and left the areas for other activities.
Predation and diminished resources during late winter may have affected activities of BWT and GWT as well.
Introduction
Blue-winged Teal (BWT; Anas discors) and Green-
winged Teal (GWT; Anas crecca) arc two of the most
common waterfowl species in North America. Most BWT
migrate to Central and South America during thenonbreeding
season, but some remain along the U.S. Gulf Coast and
overwinter with GWT and other waterfowl. This is the first
comparative study of the two species.
Most previous studies of BWT concerned breeding or
poslbreeding feeding ecology (reviewed by EhiBowy, 1985);
however, several studies were conducted recently on activi-
ties of nonbreeding GWT (Tamisier, 1976; Bakjassane and
Bolen, 1984;QuinlanandBaldassarre, 1 984; Euliss and Harris,
1987; Rave, 1987; Rave and Baldassane, 1989; Gaston, 1992).
The purpose of this study was to compare activities of BWT
and GWT concurrently, 'niisallowedustocomparcthe two
species under identical conditions, which is not possible
unless the birds are observed simultaneously. Specifically,
our goals were to (1) determine whether BWT and GWT
required similar foraging times in habitats used primarily
for feeding (inlermediale marshes), since previous studies
indicated that BWT and GWT food preferences differed
during winter (Bellrose, 1980); (2) determine whether
predators affected BWT and GWT foraging and habitat
selection, as suggested in studies of other waterfowl species
in these coastal Louisiana marshes (Gaston and Nasci,
1989); and (3) determine whether the role of their habitat
changed as food resources diminished during winter.
Materials and Methods
Blue-winged Teal were observed at the 30,756 ha
Rockefeller State Wildlife Refuge (S WR) in southwestern
Louisiana (sec Paulus, 1982). The area is closed to hunting,
public access is limited, and much of it is impounded to
control water levels.
Birds were observed from blinds (4 m high) located on
leveesadjaccnt to three intermediatemarsh impoundments.
Intermediate marshes are generally lower salinity (annual
salinity range: 0-5 ppL) than brackish marshes, and are
transition zones between salt marshes and fresh marshes.
The dominant vegetation of intermediate marshes in the
study area was wiregrass (Spartina patens), cattail (Typha
spp.), bulrush (Scirpus californicus), common reed
(Phragmites australis), andbearded sprangletop (Leptochloa
fascicularis). Levees surrounding the study areas sup-
ported d^ise stands of common reed, which allowed access
to the towers with minimal disturbance to waterfowl. The
three areas were described by Gaston and Nasci ( 1989). The
areas were generally similar, but varied in water level
ranges and pond sizes. Observadon was planned in these
similaraieasin order tocompareeCfectsof water depdi, weather,
andtonporalfdctors. Previous investigaiorscompared vastly
different habitats (e.g., Quinlan and Baldassane, 1984; Rave,
1987; Rave and Baldassane, 1989), where extreme variance
in teal bdiavior would be most likely, but effects of specific
habitat factors could not be assessed adequately.
39
40
Gaston and Nasci
Weekly observations of BWT and GWT were made
concunenily at three stations from October 1987 to March
1988. Observations were made from 15 minutes before
sunrise to 15 minutes after sunset Days were divided into
three equal time blocks (morning, midday, and afternoon),
and each time block was divided into equal numbers of 15-
minute time periods. Random numbers tables were used to
select 30 to 36 observation periods per tower each day.
Asinglescan was made during selected 15-minute time
periods with a 60x spotting scope using scan sampling
techniques (sensu Baldassarre et ai, 1988), and all BWT
and GWT within 200 m were included in the observations.
The activities {sensu Paulus, 1988) were recorded on tally
meters as resting (sleeping and loafing), feeding (ingestion
of surface or subsurface food), locomotion (swimming,
walking, or flying), courting (pair formation and social
displays), preening (body maintenance or bathing), alert
(attentive to disturbance), and agonistic activities (threat
displays). The sex of each individual was recorded. Ail teal
within view were counted during every 15-minute period to
estimate number of leal using the study areas.
During each 15-minute observation period, ambient
temperature, cloud cover, wind velocity, rainfall inteiLsity,
and light intensity were recorded. Light was measured with
an Environmental Concepts LIM 2300 light-intensity meter
mounted on a ring stand to measure reflected light from a
photographic gray card. Percent cloud cover was estimated
by the observer at Station 2, and wind velocity was mea-
sured by an anemometer at the Rockefeller SWR weather
station.
Analysis of variance ( ANO VA) and Duncan’s multiple
range test were used to test for significant differences
among activities, time blocks, andmonths. Activities were
compared among stations using ANOVA and Duncan’s lest
(BWT: Stations 1 to 3, a = 297, 254, 196; GWT: Stations
1 to3,a=264,368, 135). Specific activities and differences
between sexes (paired sets) of the two species were tested
withi-tests. Percent-time data were arcsine transformed for
these analyses. Numbers of individuals were totaled for
each time block, then percent time spent in each activity
was calculated by dividing the number of observations of an
activity by the total number of observations, times one
hundred, Pearson’s correlation analyses were used to
determine relationships between activities and physical
variables. Progressive values were used for correlations
involving factors of time: 1 to 6 for months, and 1 to 3 for
daily time periods (morning, midday, altemoon). To
compare the variables of habitat and how they affected each
species, principal components analyses were conducted on
untransformed data to determine which physical factors
varied most with activities.
Results
Activities
Observations of BWT and GWT totaled 424 hours (no
occurrence was not recorded as time). Throughout most of
the study , there were more males than females of BWT (9:1)
and GWT (10: 1) observed; however, there were no signifi-
cant differences (P > 0.05) between sexes in time spent in
any activity. Sex of BWT could not be confidently deter-
mined during October and early November, because most
BWT individuals were in eclipse plumage. Male and
female BWT observed after November were not signifi-
cantly different in their activities. Thus, sexes were not
distinguished in the analyses below.
Generally BWT spent more time (P < 0.01) feeding
(65.4%), more time (P < 0.05) alert (3.1 %), and less time
(P<0.01)resting(15.8%)thanGWT (Table 1). Therewere
nodifferences (P>0.05) between the species in locomoting,
courting, or preening activities. Feeding (BWT: 18.4 to
75.8%; GWT: 10.5 to 77.7%) was the most frequentactivity
of these species (P < 0.05) during most months, followed by
resting (8.2 to 50.9%; 5.0 to 64.1%) and locomotion (8.2 to
40.7%; 5.5 to 25.5%). Neither species spent much time
courting (until March) or alert. Agonistic behavior never
represented over 0. 12% of activities per month, and there-
fore was excluded from further analyses.
Habitat Comparisons
Stations 1 and 2 were generally similar habitats, but
Station 3 had deeper water and some different vegetation.
However, the only significant differences (£= 6.47, 2 d.f. .
P < 0.05) in activities among the three stations occurred in
BWT during December and January, when BWT at Station
2 fed less than those elsewhere (Table 2). Numbers of BWT
at Station 2 (15,533 observed) greatly exceeded those at
Stations 1 (5919) and 3 (5922). GWT were also more
numerous at Station 2 (36,782) than at either Stations 1
(7825) or 3 (3356). Relatively few BWT or GWT were
observed at Station 3 after December, probably due to high
water (greater than 1 m depth).
Temporal EfTects
During October, most BWT and GWT had a regular
pattern of morning feeding, resting during midday, and
preening for up to an hour thereafter. Few BWT or GWT
were seen using the study areas when the observers arrived
before dawn, but teal began arriving soon thereafter. Dur-
ing October and November, many BWT and GWT were
observed leaving the observation areas at Stations 1 and 3
TABLE 1
Activity budgets by month for Blue-ivinged Teal and Green-Winged Teal wintering at Rockefeller SWR, (Cameron Parish, Louisiana).
Ecology of Two Waterfowl Species
41
Calculated from total numbers of individuals observed.
42
Gaston and Nasq
TABLE 2
Activi^ budgets by month and station for Bine-winged Teal (BWT) and Green-winged Teal (GWT) wintering
at Rockefeller SWR, Louisiana.
Activity
Station
October
November
December
January
February
March
Resting
1 (BWT)
18.2
8.5
2.5
7.3
17.1
50.1
1 (GWT)
43.6
10.7
-
9.4
15.0
34.9
2 (BWT)
15.7
8.2
17.9
28.3
7.2
—
2 (GWT)
14.6
2.9
64.2
33.0
5.1
-
3 (BWT)
13.9
19.5
0
0
-
—
3 (GWT)
15.8
10.2
0
82.4
-
-
Feeding
1 (BWT)
46.0
70.9
70.0*
76.9*
63.7
18.4
1 (GWT)
31.0
71.0
-
71.6
70.7
29.3
2 (BWT)
69.2
67.4
11.9^
41.7"
673
-
2 (GWT)
75.4
78.1
10.5
51.1
79.6
-
3 (BWT)
68.6
68.3
50.0*
963*
-
~
3 (GWT)
66.3
77.3
0
11.8
-
-
Locomotion
l(BWT)
12.5
15.0
18.8
9.9
9.6
10.9
1 (GWT)
8.2
12.2
-
15.7
63
253
2 (BWT)
9.1
14.5
68.7
26.7
17.0
—
2 (GWT)
4.5
12.1
19.8
10.9
9.8
-
3 (BWT)
2.9
2.7
25.0
0
-
-
3 (GWT)
3.0
9.4
0
0
-
-
Courting
1 (BWT)
2.6
0
0
0.1
1.9
6.0
1 (GWT)
0
0
-
0
1.2
2.8
2 (BWT)
0
0
0
0
0
-
2 (GWT)
0
0
03
2.1
1.2
-
3 (BWT)
0.7
0
0
3.9
-
-
3 (GWT)
0.1
0
0
0
-
—
Preening
1 (BWT)
13.5
3.2
0
4.9
7.4
12.2
1 (GWT)
10.7
4.0
-
2.0
6.3
0.9
2 (BWT)
2.9
9.7
13
33
6.0
-
2 (GWT)
4.9
5.8
53
2.9
33
—
3 (BWT)
10.0
9.6
25.0
0
-
-
3 (GWT)
9.1
3.2
99.0
5.9
-
-
Alert
1 (BWT)
7.2
2.4
8.8
0.9
0.4
1.7
1 (GWT)
6.6
2.1
~
1.3
0.3
6.6
2 (BWT)
3.0
0.2
0
0
2.4
-
2 (GWT)
0.6
1.0
0
0.1
1.2
-
3 (BWT)
3.9
0
0
0
-
-
3 (GWT)
5.8
0
1.0
0
--
--
a,b,c Percentages for each station denoted by different letters are significantly different (P < 0.05).
EC0LCM3Y OF Two Waterfowl Species
43
after morning feeding, presumably to rest elsewhere. Hun-
dreds of BWT and GWT were observed resting in densely
vegetated salt marsh areas (outside the study area) near
Station 3 during midday . Similarly, most resting within the
observation areas occurred during midday (Table 3).
The greatest differences in activities between the two
speciesoccurred during December, whcnGWT spent 64. 1 %
of the time resting and BWT spent only 9% of the time
resting (Table 1). After December, BWT and GWT loco-
motion was most frequent during morning (Table 3). Time
spent courting and alert did not differ (P > 0.05) among time
blocks in either species.
Physical and Biological Factors
(jenerally BWT and GWT responded to physical con-
ditions in similar manners. In both species, resting and
feeding were highly correlated (BWT: a = 747; GWT: jq =
767; P < 0.01) with temperature (+) and light intensity (-).
Locomotion was highly correlated with light intensity (-),
and preening was highly correlated with temperature (+;
Table 4). However, the responses of the two species to
physical conditions were not identical. Locomotion was
highly correlated with rainfall intensity (+) only in BWT.
Preening was most closely correlated with lime of day in
BWT, but not so in GWT. Courting by GWT was related
(P < 0.0 1) to both temperature (-) and liglii intensity (-), but
the factors were not related (P > 0.05) in BWT. The
significant relationships among feeding, resting, preening,
temperature, and light support the observations of teal
resting and preening after morning feeding. The consistent
pattern of afternoon preening during early months of the
study accounted for the inverse relationship (P < 0.01)
between preening and date. Not unexpectedly, courting
increased (P < 0.01) during the study period (Table 4) and
was most frequent in March (Table 1).
Principal components analysis was conducted on a
matrix of percent time spent per activity and physical
variables including data from all stations and time blocks.
The BWT first principal component (PC I) showed load-
ings with five variables: water depth, month, temperature,
light intensity, and cloud cover (Table 5). In GWT, the first
principal component (PC-I) showed high correlation with
four variables: month, temperature, light intensity, and
cloud cover (Table 5). The correlation with so many
variables indicates that the aciiviiies of both species gener-
ally varied as a group. PC-II was not highly correlated witli
any variables. Thus, mosiseparationof the BWT and GWT
activities occurred along a single axis (vertical) when the
first two principal component scores were plotted in two
dimensions (Figure I). In both species, feeding and resting
were separated from other activities, indicating that physi-
cal data (especially temperdlure and light iniensiiy, Table
4) were very useful in mterpreting teal feeding and resting
behavior. Several factors (cloud cover, time, temperature,
and light intensity) also distinguished the activities (hori-
zontally), but to a lesser degree. Together PC-I and PC-II
accounted for 36.7% of the variance in BWT and 35.4% in
GWT.
Discussion
Feeding values of BWT (65.4%) were similar to those
reported during poslbreeding (68.6%, DuBowy, 1985) and
incubating (60%, Miller, 1976), and GWT values (55.3%)
were similar to those for GWT feeding in natural marshes
of Soulh Carolina (56%, Hepp, 1982). However, GWT
feeding values were well above averages reported else-
where along the Gulf Coast (Texas, < 23%, Quinlan and
Baldassarre, 1984; Louisiana, 33.3%, Rave and Baldassarre,
1989). Some of the discrepancy among studies likely
resulted from variation in the habitats studied. For example,
studies in Texas were conducted in agricultural areas where
less foraging may be necessary to meet metabolic needs
( < 23%, (Juinlan and Baldassarre, 1984). Also, inclusion
of several habitats in a study may lower the overall values
for time spent feeding, assuming the activities vary with
habitat. We used only intermediate marshes for our study.
Rave and Baldassarre (1989), who also studied GWT on
Rockefeller SWR, observed at several habitats, including
intermediate marshes where GWT fed 41,3% of the time.
Overall, BWT spent more lime feeding (65.4%) than
GWT (55.3%). Bcllrose (1980) reported that these two teal
species often feed together, although GWT have a greater
preference for seeds, and species that feed on seeds may
allocate less time to feeding (Paulus, 1984). Gut contents
of BWT and GWT collected during the study period
indicated they fed on similar diets, primarily of wild seeds
and chironomids, and seldom ingested agricultural seeds.
Therefore, though the differences between the two species
in time spent feeding could have resulted solely from
greater preference for seeds by GWT, we suggest that the
differences resulted from di.screpancies in selections of
habitats as well.
The frequency of feeding and locomotion of both
species increased with decreasing temperatures (Table 4),
probably aresponsetogreaiermetabolic needs (Jorde etal,^
1983), but perhaps also because food availability decreased
from fall to winter. At Rockefeller SWR, chironomid and
.seed denaties diminished from fall to winter in ihe three
study areas (Gaston and Nasci, 1989). Mean number of
chironomids during fall (October to December) was 912
m'^ (range 20 to 2422 m*^), while winter (January and
February) means were 365 chironomids m (range, 60 to
760 m*’). Total number of seeds averaged 8917 m-^ during
the fall (range, 1240 to 23,660 m'^) and 4075 m*^ (range,
2400 to 6650 m*^) during the winter.
44
Gaston and Nasq
TABLE 3
Activity budgets by month and time of day for Blue-wii^ed Teal (BWT) and Green-winged Teal (GWT)
wintering at Rockefeller SWR, Louisiana.
Activity
Time
October
November
December
January
February
March
Resting (BWT)
Morning
6.2
12.7
0
10.8
15,4
23.9
Midday
26.2
14.7
30.0
6.9
7.9
70,0
Afternoon
15.9
26.6
6.9
17.7
29.7
42.1
Resting (GW’O
Morning
11 . 9 ^
9.0*
15.1*
13.4*
16.7*
-
Midday
63.3*^
IS - tf *
48.8'*
37. r *
5.6**
-
Afternoon
15.5*
12.2'*
52.21*
18.8*
21.5*
29.8
Feeding (BWT)
MonnDg
76.8*
70.8*
72.0*
71.0*
45.4*
30.8*
Midday
54.8*^
72.1*
30.0^
66.^*
77.1'*
00
Afternoon
60.9^
55.3'>
29.^
62.7“
53.9*
23.6^*
Feeding (GWT)
Morning
76.1*
68.6*
50.0*
59.5*
53.4*
~
Midday
25.3*'
48.5^
24.4'*
43.6 f *
84.2'*
-
Afternoon
63.6*
67.8*
25.1“
64.8*
63.3*
26.7
Locomotion (BWT)
Morning
8.8
13.1*
14.6*
17.9*
25.9*
23.2*
Midday
10.1
2.6'*
40.0^*
16.3*
8.1'*
6.3'*
Afterooon
8.7
ll.T'*
515“
7.9“
7.6**
12.^
Locomotion (GWT)
Morning
4.8
17.6*
21.1
21.0
22.8*
-
Midday
0.9
25.7'*
21.4
155
5.0^
-
Afternoon
7.1
14.3*
19.4
10.0
6.6'*
33.2
Conning (BWT)
Morning
0.3
0
0
0
2.6
12.6
Midday
0.8
0
0
4.2
0.6
3.0
Afternoon
0.3
0
0
0.2
0.6
5.4
Courting (GWT)
Morning
0
0
0.1
4.0
1.3
-
Midday
0.1
0
0.8
0.9
1.3
-
Afternoon
0.1
0
0
0.8
0.8
2.7
Preening (BWT)
Morning
3.4
2.5
0
0.2
7.9
95
Midday
6.8
10.6
0
1.4
35
11.4
Afternoon
9.3
6.3
6.3
112
7.4
12.9
Preening (GWT)
Morning
4.5*
4.7
13.7*
1.8
3.2
-
Midday
9.3'*
6.1
4.6“
1.2
3.8
-
Afternoon
8.7*’
4.5
3.4“
4.0
7.4
0.9
Alert (BWT)
Morning
4.5
0.9
13.4
0.1
2.8
0
Midday
1.2
0
0
4.6
2.9
0.4
Afternoon
4.8
0
5.6
0.3
0.9
3.3
Alert (GWT)
Morning
2.6
0
0
0.3
2.6
-
Midday
1.1
1.1
0
1.1
0.1
-
Afternoon
5.1
1.2
0
15
0.4
6.7
a,b Percentages for each time of day denoted by different letters are significantly different (P < 0.05).
Ecology of Two Waterfowl Species
45
TABLE 4
Correlation coefficients of selected physical variables and activities of Blue-winged Teal and Green-winged
Teal wintering at Rockefeller SWR, Louisiana.
Variable
Resting
Feeding
Blue-winged Teal
Locomotion
Courting
Preening
Alert
Date
0.073
-0.087*
0.106*
0.139**
-0.001
-0.028
Time
0.102*
-0.142*
-0.047
-0.026
0.172**
0.034
Rainfall
-0.045
-0.022
0.238**
-0.026
-0.086*
0.053
Wind
-0.005
0.007
-0.107*
-0.060
0.081*
-0.021
Temperature
0.186**
-0.193**
-0.121**
0.011
0.139**
0.028
Light intensity
0.138**
-0.118**
-0.141**
-0.005
0.085*
-0.015
Cloud Cover
-0.144**
0.076
0.141**
-0.056
-0.047
0.050
Green-winged Teal
Variable
Resting
Feeding
Locomotion
Courting
Preening
Alert
Date
-0.062
-0.055
0.156**
0.241**
-0.125**
-0.065
Time
0.047
-0.032
-0.097*
-0.105*
0.036
0.091*
Rainfall
0.004
-0.073
0.059
0.077
0.027
-0.003
Wind
-0.059
0.063
-0.085*
-0.062
0.005
0.009
Temperature
0.213**
-0.127**
-0.063
-0.159**
0.155**
0.030
Light intensity
0.393**
-0.210**
-0.158**
-0.136**
0.151**
-0.027
Cloud Cover
-0.112*
0.002
0.010
0.057
-0.018
0.053
P < 0.05
P < 0.01
Activity budgets of BWT and GWT were similar
among the three areas we studied, even though the habitats
varied somewhat in water depth and related variables. We
had much less habitat diversity for comparisons than in
previous studies in Texas (White and James, 1978), Ala-
bama (Turnbull and Baldassanre, 1987), or Louisiana (Rave
and Baldassarre, 1989) where investigators demonstrated
significant differences in activity budgets of waterfowl
using widely different habitats.
The inverse relationship between feeding and tempera-
ture (Table 4) stresses the impact of cold fronts, morning
low temperatures, and decreasing temperatures on teal
activities. Highest numbers of BWT were observed during
October and November, indicating that most of them were
on migration flights and later left the area. Thus, since many
of the BWT probably arrived in the smdy areas in associa-
tion with weather fronts (as suggested by Bellrose, 1980),
the relationship between feeding and tcmperauiie was not
unexpected. The lack of close correlations between time of
day and feeding or resting of the leal (Table 4) emphasizes
the loss of pattern in activities after fall. Wc suggest this
occurred because metabolic demands increased after De-
cember, and because seeds and chironomids, which had
been abundant in the study areas during the fall, were more
46
Gaston and Nasq
TABLE S
Correlations with first and second principal components based on physical variables and activities of
Blue-winged Teal and Green-winged Teal wintering in southwestern Louisiana.
! Blue-winged Teal
1
1
1
, Green-winged Teal
Physical Variables
! PC-I
1
pc-n
1
1
PC-I
PC-fl
Water Depth
1
1
j -0.51
-0.33
1
1
1
1
1
-0.27
-0.11
Date
j 0.73
0.33
1
1
0.78
0.22
Time
j -0.31
0.30
1
1
-0.24
-0.23
Rainfall Intensity
j 0.50
0.11
1
1
0.40
0.34
Wind Velocity
! -0.03
0.08
1
1
0.01
-0,31
Temperature
j -0.84
0,16
1
1
-0.84
-0.02
Light Intensity
j -0.79
0.03
1
1
-0.84
0.08
Cloud Cover
1 0.69
t
1
0.02
1
1
1
0.62
0.04
scarce after December. This scarcity in food probably
accounted for the increased time spent in locomotion during
late winter and early spring mornings (Table 3). Appar-
ently, since food was scarce, the B WT and GWT spent more
time in search of feeding areas or spent more time feeding
elsewhere.
Both teal species fed more during the mornings than
during (he afternoons. This pattern was especially evident
during the fall (Table 3) when thousands of migrating BWT
actively fed in the area. Several hypotheses could be
propos^ to explain the pattern of morning feeding. Per-
haps some teal were arriving during morning (migrants) or
were fasting ovemight.asproposedbyRaveand Baldassarre
(1989). Perhaps most of the teal left the study area after
morning feeding, and those that remained fed little because
they had met their metabolic requirements. Perhaps morn-
ing feeding was more efficacious than midday or afternoon
feeding because of less predation pressure during morning.
Eulissand Harris (1987) hypothesized that disturbance
by Northern Harriers (Circus cyaneus) played a major role
in diumal activities of GWT. However, Gadwalls (Anas
strepera) feeding in the same study area were not disturbed
by the presence of Northern Harriers (Gaston and Nasci,
1989). We ob.served that Northern Harriers caused both
BWT and GWT in our study areas to take flight regularly,
and Northern Harriers were especially active during mid-
day and afternoon. Significantly greater morning feeding
by these teal is consistent with the hypothesis that predation
pressure influenced the time of day that teal fed, and may
account for the use of refuge vegetation during resting
periods.
There were differences in overall time spent feeding,
resting, and alert bet ween BWT and GWT, but the daily and
monthly patterns inactivities were generally similar and the
role of habitat remained unchanged during the study. The
study area provided resources for both species, and both
apparently used the area for most of their feeding. How-
ever, BWT and GWT responded differently to certain
environmental and habitat conditions. As food was de-
pleted during middle and late winter, many GWT left the
shallow intermediate marsh ponds and fed in salt marsh
mudflats (see Gaston, 1992). Those BWT and GWT that
remained in the study area spent more time foraging for
diminishing resources. During our study, many GWT used
salt marshes for midday resting and preening. BWT did not
use mudflats or salt marsh areas as often, and either u sed the
intermediate marshes for all of their activities or emigrated
from the study area (i.e., across the Gulf of Mexico).
Acknowledgments
We are grateful to the personnel at Rockefeller S WR
for their support and interest throughout the study, espe-
cially T. Joanen, D. Richard, T. Hess, and L. McNease.
Rockefeller SWR provided boats, fuel, field supplies,
meals, and lodging forthe project We also thank McNeese
students J. Pitre, K. Savoie, and L. Vandemiolen for their
assistance in field observations, and J. DeRouen, J. Carter,
J. Wing, L. Vandermolen, and J. Pitre for their help in the
laboratory. This project was funded by the Louisiana Board
of Regents* Research and Development Program.
Ecology of Two Waterfowl Species
47
BLUE-WINGED TEAL
GREEN- WINGED TEAL
Figure 1. First (abscissa) and second (ordinate) unrotated e^envectors of a principal components analysis of Blue-winged Teal
and Green-winged Teal activities and associated physical variables in southwestern Louisiana.
48
Gaston and Nasq
LrreRATURE CriED
Baldassaire.G.A. and E.G. Bolen. 1984. Field feeding ecology
of waterfowl wintering on the Southern High Plains of
Texas. J. WildL Mgmi, 48:63-71.
Baldassarre, G.A., S.L. Paulus, A. Tamaisier and R.D. Titman.
1988. Workshop summary: techniques fortiming activity of
wintering waterfowl, pp. 181-188. In-. Waterfowl in winter
(M.W. Weller, ed,). University of Minnesota Press, Minne-
apolis.
Bellrose,F.C, 1980. Ducks, Geese, and Swans ofNoith America.
Third ed. Staclqx>le Books, Harrisburg, Pennsylvania. 543 pp.
DuBowy,PJ. 1985. Feedingecologyandbehaviorof postbreeding
Blue-winged Teal and Northern Shovelers. Canadian J.
Zoai. 63:1292-1297.
Euliss.N.H.andS.W. Harris. 1987. Feeding ecology of Northern
Pintails and Gieen-winged Teal wintering in California. J.
Wildl.Mgmt, 51:124-732.
Gaston, G.R. 1992. Green-winged teal ingest epibenthic
meiofauna. Estuaries 15:227-229.
Gaston, G.R. and J.C.Nasci. 1989- Diurnal time-activity budgets
of nonbreeding Gadwalls {Anas streperd) in Louisiana.
Proc. Louisiana Acad. Sci. 52:43-54.
Hepp, G.R. 1982. Effects of environmental parameters on the
foraging behavior of three species of wintering dabbling
ducks (Anatini). Canadians, Zool. 63:289-294.
Jorde, D.G,, G.L, Krapu and R.D. Crawford, 1983. Feeding
ecology of Mallards wintering in Nebraska. J. WildL Mgmt.
47:1044-1053.
Miller, K.J. 1976. Activity patterns, vocalizations, and site
selection in nesting Blue-winged Teal. Wilc^owl 27:33-
43.
Paulus, S.L. 1982. Feeding ecology ofGadwalls in Louisiana in
winter. J. WildL Mgmt. 4611-79.
. 1984. Activity budgets of nonbreeding Gadwalls in
Louisiana. /. WildL AfgmT. 48:371-380.
. 1988. Time-activity budgets of nonbreeding Anatidae: a
review, pp. 135-152. In: Waterfowl in winter (M.W.
Weller, ed.). University of Minnesota Press, Minneapolis.
Quinlan, E.E. and G. A. Baldassarre. 1984. Activity budgets of
nonbreeding Green-winged Teal on playa lakes in Texas. J.
WildL Mgmt. 48:838-845.
Rave, D.P. 1987. Activity budgets of Green-winged Teal
wintering in coastal wetlands of Louisiana. Unpub. M.S.
Thesis, Auburn University, Auburn, Alabama. 28 pp.
Rave, D.P.andG.A. Baldassarre. 1989. Activity budget of green-
winged teal wintering in coastal wetlands of Louisiana. J.
WiUL Mgmt. 53:753-759.
Tamisicr, A. 1976. Diurnal activitie.s of green-winged teal and
pintail wintering in Louisiana. Wildfowl 27:19-32,
Turnbull, R.E. and G.A. Baldassane. 1987. Activity budgets of
Mallaids and American Wigeon wintering in east-central
Alabama. Wilson Bull, 99:457-464.
White, D.H. and D. James. 1978. Differential use of fresh water
environments by wintering waterfowl of coastal Texas.
Wilson BulL 90:99-111.
Gulf Research Reports
Volume 9 | Issue 1
January 1994
Fatty Acid Pattern Differences Among Individuals of Two Estuarine Fishes (Leiostomus
xanthurus Sind Mugil cephalus)
Julia S. Lytle
Gulf Coast Research Laboratory
Thomas F. Lytle
Gulf Coast Research Laboratory
DOI: 10.18785/grr.0901.05
Follow this and additional works at: http:/ / aquila.usm.edu/ gcr
Part of the Marine Biology Commons
Recommended Citation
Lytle; J. S. and T. R Lytle. 1994. Fatty Acid Pattern Differences Among Individuals of Two Estuarine Fishes (Leiostomus xanthurus and
Mugil cephalus). Gulf Research Reports 9 (l): 49-56.
Retrieved from http://aquila.usm.edu/gcr /vol9/issl/5
This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf and Caribbean
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Gtdf Research Reports, Vol. 9. No. 1. 49-56, 1994
Manuscript received January 26, 1993; accepted April 29, 1993
FATTY ACID PATTERN DIFFERENCES AMONG INDIVIDUALS OF TWO
ESTUARINE FISHES (LEIOSTOMUS XANTHURUS AND MUGIL CEPHALUS)
JULIA S. LYTLE AND THOMAS V. LYTLE
Gulf Coast Research Laboratory, P.O. Box 7000, Ocean Springs, Mississippi
39566-7000
ABSTRACT Ten individual fish of two estuarine species, spot {Leiostomm xanthurus) and striped mullet (Mugil
cephalus), were analyzed for fatty acids. Fish of similar size were obtained from a single collection to minimize
variability due to age, size, location and season. Analysis of variance (ANOVA) of each fatty acid provided
statistically similar groups for each acid that existed among individual fish. Fatty acids in the striped mullet
provided a greater numb^ of statistically similar groups than those in spot, 'mdicating greater variability among
individual striped mullet, which probably reflected a greater diversity in the feeding regime for this species,
ANOVA results within classes of fatty acids of both species indicated greater diversity in monounsaturated and
polyunsaturated than saturated fatty acids. Eicosapentaenoic acid (EPA) showed more mdividual variability in both
species than did docosahexaenoic acid (DHA). Dietary lipids and metabolic needs of the two species are distinct
and may be the key factors in explaining individual differences observed in these two fish species.
Introduction
Natural populations of fishes contain fatty acids and
other nutritional components that are highly variable.
Stansby (1981) has addressed some sources of variability in
fatty acid composition of fish oils within a given species.
Other studies have focused on individual species and
variations with respect to age (Hayashi and Tal^gi, 1978),
season (Ueda, 1976; Hayashi and Takagi, 1977. 1978;
Gallagher et ah, 1989), size (Gallagher et al., 1984) and
geographical location (Addison et «/., 1973; Whyte and
BoutiUier. 1991), but have not addressed variations among
individuals of these species. Assessing importance of these
variables is dependent upon appraisal of individual vari-
ability, since inherent biochemical differences exist from
fish to fish even when al! other variables are minimized. It
was essential that specimens be carefully selected of two
species of coastal Gulf finfishes which differed little in size,
development stage, weight or location of catch. This
selection permitted specific examination of those fluctua-
tions in individual fatty acids that may occur due only to
individual differences. By using a non-random selection
process for samples, results could not be used to character-
ize overall trends in the two species. However, it was felt
that results would define some mdividual variations that are
uniquely characteristic for these two fishes that would
permit informative and useful comparisons to be made and
that suggestions for these variability differences would be
suitable.
Two species of coastal Gulf finfishes, spot and striped
mullet, were chosen for assessing mdividual variability
because they met several criteria. They represented fishes
with differcni feeding regimes, they were collected easily
in large numbers from a given area in one catch, and they
were numerous enough to permit selection of fish having
little variation in size. Additionally, the biology of spot
(Gunter, 1945; Dawson, 1958; Hodson etal., 1981; Chest-
nut, 1983; Sheridan et al.y 1984) and striped mullet (Odom,
1966; Thompson, 1966) is well established, and both
species are found abundantly in local coastal estuaries.
Spot is a dominant bottom fish and is considered to feed
in schools over sand-mud bottoms on polychaeies,
harpacticoid copepods, bivalves and possibly some detritus
(Hildebrand and Schroeder, 1928; Darnell, 1958; Hodson
et al., 1981). Spot has a fairly small mouth and possesses
gill rakers that permit retention of small food particles and
prevent ingestion of relatively large food items such as fish,
shrimp and crabs (Darnell, 1958; Hodson et al., 1981;
Chesmut, 1983; Sheridan et al., 1984).
On the other hand, the striped mullet begins its life by
eating planktonic plants and animals, but it changes its diet
to include a broad range of detritus and plant material as it
develops (Moore, 1974). It filler-feeds above organic muds
containing microplant material and macroplant detritus
(Odum, 1966, 1970), and it is generally considered to be a
broad spectrum herbivore. Occasionally, however, car-
nivorous feeding has been observed in striped mullet (Bishop
and Miglarese, 1978),
Fatty acids in marine dietary lipids, whether plant or
animal, serve as an energy source for metabolism and
provide polyunsaturated fatty acids (PUFA) essential for
membrane structure and function. Lipids in muscle tissue
of fish generally reflect those fatty acids obtained from the
diet. Since these two species have a widely different natural
diet, they provide an opportunity to examine mdividual
variability within and between species.
49
50
Lytle and Lytle
Materials and Methods
Collection
Striped mullet were collected on January 21, 1988 in
the shallow estuary of Biloxi Bay, Mississippi. Spot were
collected on April 13, 1988 at Ship Island, a barrier island
15 miles south of Gultjport, Mississippi, in the northeastern
Gulf of Mexico. All fish were collected by gill net and
maintained on ice until examined. Standard lengths were
measured and weights recorded. Fish of approximately the
same size were filleted and individual Unplaced separately
in polyethylene bags, flushed with Nj, rapidly frozen and
stored at *20°C. Average body weight of striped mullet was
230 g (± 12% relative standard deviation: RSD) and average
standard length was 22 1 mm (±4.5%RSD). Average body
weight of spot was 147 g (±5.2%RSD), and average stan-
dard length was 174 mm (±3.5%RSD).
Analytical Procedure
All solvents used in analysis were HPLC grade or
analytical reagent grade. Standards were purchased from
NuCheck Prep, Inc. (Elysian, MN). Fillets were
homogenized using a Waring blender and 0.5 g aliquots
weighed into screw-capped (Teflon-lined) centrifuge tubes
(30 ml) and saponified at ambienttemperature withethanolic
KOH under Nj using a magnetic stirrer for one hour. Care
was exercised in the volumes of saponifying mixtures used
to keep the water level, derived from tissue, sufficiently
high to prevent trans-esterification. Solvent ratios were
those suggested by Nelson (1966). After dilution with
distilled water, the neutral fraction was extracted with
hexane. The remaining alkaline solution was acidified with
6N HCI. and free fatty acids were extracted with benzene.
Benzene aliquots were combined and concentrated using a
rotary evaporator. All evaporations were closely monitored
to ensure that distillation temperatures did not exceed 25®C.
Fatty acids were converted to methyl esters using 7% BF^-
MeOH by the method of Metcalfe et al (1966) modified to
use ambient temperatures and a one-hour reaction period.
Identification of fatty acid methyl esters (FANE) was
obtained by capillary gas chromatography (GC) using a
Perkin-Elmer model Sigma 2000 gas chromatograph
equipped with flame ionization detector and fined with a
30 m X 0.25 mm i.d. fused silica capillary column coated
with a 0.25 m film thickness of Dura Bond WAX (J & W
Scientific) and operated with a split ratio of 100:1. The
carricrgas.He.wasmaintainedatiopsi, Oven temperature
was programmed at 90-250‘^C at a linear rate of 4°Aninute.
Data was processed using a Perkin-Ehner Sigma 10 data
system with quantification of ah compounds based on
individual peak area response by GC compared to the
internal standard methyl tricosanoate. Quantitative data
were corrected for differences in detector responses that
were determined through analysis of authentic standards of
each reported fatty acid. FAME were tentatively identified
by comparison with retention times with those of authentic
standards. Verification of identification on select samples
was accomplished through gas chromatography mass spec-
trometry analysis conducted by National Marine Fisheries
Service, Charleston Laboratory. Concentrations of indi-
vidual isomers of PUFA were separately tabulated; separate
isomers of monounsaturates (e.g. 18:1) were not reported.
Sample Protection
Several precautions were taken to ensure that no
degradation or other alteration of lipids occurred during
extraction and saponification. All analytical steps were
conducted at ambient temperatures, and samples were
constantly flushed with N^ to prevent oxidation. Further, as
many steps as possible were conducted in a single extraction
mbe to reduce loss and degradation that occurs with sample
transfer. All solvents were flushed with N^ immediately
before use to remove dissolved and to prevent oxidative
degradation. Likewise, samples requiring storage were
placed in sample bags which were flushed with N^ before
being frozen (-20®C). In addition, the antioxidant butylated
hydroxytoluene (BHT) was added in a concentration of
0.005% (w/v) to extraction solvents to prevent oxidative
degradation of unsaturaied lipids.
Data Analysis
One way analysis of variance (ANOVA) with post
facto 95% confidence level range test (Statistical Graphics
Corporation, 1988) was used to compare individual fatty
acids as well as certain parameters d^ved from fatty acid
data of individual fish. Similarity groups were established
of individuals for each variable which were statistically
indistinguishable (p<0.05). In addition, the number of
groups was tallied as a further measure of individual
variability.
Results
Figures 1 and 2 depict mean concentration of fatty
acids in the samples of individual spot and striped mullet as
well as mean % composition of total saturated,
monounsaturaied and PUPA. Figures 1 and 2 also include
the standard deviations of the means of the ten individual
fish and are shown by the dark bars in the graphs. Concen-
trations are shown in both wt% of the total fatty acids and
Fatty Acid Variations in Two Estuarine Fishes
51
Wt% /jg/g(1000)
■ Meal y SD
Figure 1. Leiostomus xanthurus. Distribution of fatty acids in spot. Empty bars to the left represent mean concentrations in
wt% of total reported fatty acids of 10 individual fish. Bars to the right depict mean concentrations in pg/g (wet tissue). Gray
bars are standard deviations computed on the mean of the 10 mean values for individual fish.
t
H Mean ^ SD
Figure 2. Mugil cephalm. Distribution of fotty acids in striped mullet See caption for Figure 1.
52
Lytle and Lytle
in absolute concentrations of pg/g of wet tissue. Absolute
concentrations are useful when assessing muscle tissue for
nutritive value, particularly for omega-3 (n-3) content,
since there is an increased interest in possible health
benefits (Lands, 1986), while weight percent concentra-
tions are useful in assessing biochemical significance of
fatty acid distributions.
Tables 1 and 2 contain fatty acid data computed on a
wt % basis for fatty acids in muscle tissue from spot and
striped mullet, respectively . Also included are sununations
and ratios that are helpful in characteriz'mg fatty acid
profiles in finfish. Superscripts signify the statistically
similar group(s) that each individual fish falls within for
ANOVA treatment of each fatty acid or fatty acid param-
eter. At the end of each row is the number of groups
produced by ANOVA examination of that fatly acid.
Individuals of both species varied in fat content. Striped
mullet ranged from 1.82-6.38%, while spot ranged from
4.75-8.10%.
Fatty Acid Distribution in Spot and Striped Mullet
Fatty acid profiles (Figures 1 and 2) were similar from
bodi species, particularly in content of saturated fatty
acids. Hexadecanoic acid (16:0) was dominant, followed
in decreasing order by octadccanoic acid (18:0) and
tetradecanoic acid (14:0). The remaining saturated acids
constimted less than one percent of the total fatty acids.
The predominant monounsaiuraied acid in both fish was
16: 1 . Relative to 16: 1, the contents of 18; 1 and 20: 1 acids
were higher in spot than in striped mullet, whether ex-
pressed in wt% or pg/g. The two principal PUFA in both
fishes were eicosapentaenoic acid (EPA, 20:5n-3) and
docosahexaenoic acid (DHA, 22:6n-3). These n-3 PUFA
constitute a higher percentage of the total fatty acids of
striped mullet (23 J%) than the spot (13.5%), although in
absolute concentration, these PUFA are enriched in spot
(4,530 pg/g) relative to striped mullet (3,120 pg/g). A
narrow range (2.25 to 2.86%) as well as low concentration
of arachidonic acid (AA, 20;4n-6) was found in spot,
whereas a wider range and higher concentrations (1.70-
7.00%) were found in striped mullet.
Statistical Comparisons of Component Fatty Acids
Octadccanoic acid, 18:0, was the second most domi-
nant saturated fatty acid in both spot and striped mullet. In
spot, no significant difference in values was found among
any of the individual fish (i.e. only one similarity group
shown in Table 1). On the other hand, there were seven
statistically similar groups for 18:0 in striped mullet
(Table 2). Minor saturated components, 20:0 and 22:0 in
striped mullet (22:0 in spot), showed no significant differ-
ences among any of the ten individual fish. Except for 22: 1
in spot, each monounsanirate in both spot and striped
mullet showed high diversity among individual fish (four
to six similarity groups). Among the PUFA, there were
more ANOVA similarity groups for EPA in both spot and
striped mullet than for DHA, indicating a greater diversity
of EPA than DHA in muscle tissue. In striped mullet,
ANOVA treatment of arachidonic (20:4n'6), iinolenic
(18:3n-3) and octadecanoic acid (18:0) each produced
seven similarity groups, the most diverse fatly acids in
either fish.
Fatty Acid Classes
Figures 1 and 2 indicate that both fishes showed a
prevalence of monounsaturates, with spot having 46%
monoonsaturated, 23% PUFA and 31% saturated, as com-
pared to 40%, 31%, and 29%, respectively, for these fatty
acid classes in striped mullet. The saturates for both fishes
were less diverse than for either the monounsaturates or
PUFA, Likewise, the average value of ANOVA similarity
groups for individual saturated fatty acids was less than that
found for either of the other fatty acid classes in both spot
and striped mullet.
Fatty acids occurring in concentrations above 1% of
total fatty acids showed a higher degree of individual
variability than fatty acids occurring in less than 1% for both
spot and striped mullet. The average number of similarity
groups for all fatty acids whose concentrations are above
1 % was 3.8 for spot and 5.0 for striped mullet, with 2.5 and
4.3 groups for fatty acids comprising less than 1%.
Fatty Acid Parameters
Total n-3/n-6 ratio showed little variation among
individual spot with ANOVA, separating into only two
statistically similar groups. Excluding individual spot No.
1, no di-stinclion occurred among individuals (Table 1).
Conversely, the separate sums of n-3 and n-6 fatty acids in
spot were separated into five and three similarity groups,
respectively. The n-3/n-6 ratio also varied less among
individual striped mullet (four groups) than the separate
total n-3 and total n-6 fatly acid parameters (five and seven
groups, respectively). ANOVA treatment applied to total
PUFA in both spot and striped mullet produced five
similarity groups. In spot, the unsaturated/saturated and
(EPA+DHA)/n-3 parameters produced two and four
ANOVA groups, but in striped mullet, it was four and six
groups. ANOVA treatment separated the calculated
parameters of striped mullet into a largernumberof groups
than those of spot, demonstrating the higher degree of
individual diversity for component fatty acids in the
striped mullet.
TABLE 1
Leiostomus xanthurus. Fatty acids in spot Entries are means for three replicate analyses of homogenized muscle tissue from each of 10 individual fish.
Values in parentheses are % relative standard deviations. Entries In rows sharing the same supercript letter are not statistically different (p<0.05) and are
referred to as similarity groups; group numbers refer to numbers of similarity groups computed for each fatty add.
Fatty Aod Variations in Two Estuarine Fishes
53
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