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BULLOUGH, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: Macmillan.

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Konn, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee region of Ceylon.
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Koun, A. J. 19606. Spawning behaviour, egg masses and larval development in Conus from the Indian Ocean.
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THIELE, J. 1910. Mollusca: B. Polyplacophora, Gastropoda marina, Bivalvia. In: SCHULTZE, L. Zoologische
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(continued inside back cover)

ANNALS OF THE SOUTH AFRICAN MUSEUM
ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 72 Band
January 1977 Januarie
Barts) 7), Weel

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA
(PISCES : CLUPEIDAE)

By

ELIZABETH LOUW
&
Mo J. Or rOOLE

Cape Town Kaapstad

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LARVAL DEVELOPMENT OF SARDINOPS OCELLATA
(PISCES: CLUPEIDAE)

By
ELIZABETH LOUW
South African Museum, Cape Town

&

M. J. O'TOOLE

Sea Fisheries Branch, Walvis Bay*

(With 11 figures and 3 tables)

LMS. accepted 23 August 1976]

ABSTRACT

The development of yolk-sac, larval and metamorphic stages of Sardinops ocellata (Pappe)
are described, together with notes on the transition to juveniles. Emphasis is placed on changes
in body proportions, pigmentation, fin development and fin position relative to myotomes
during development.

CONTENTS

PAGE

Introduction : : : 3 ; bi A)
Material and methods 2 ; ; : 127
General description . 3 : 5 29
Yolk-sac stage larvae. : : el29
Manvaci 5 ; : : ; : 132
Metamorphic stage larvae. : a) 1ske)
Juveniles . : ; : : : : 143
Discussion . ; : ‘ ‘ : . 144
Acknowledgements . : ; : ; 144
References . 2 : : : ; ga) ale)

INTRODUCTION

The pilchard or sardine, Sardinops ocellata (Pappe), has for about 30 years
been of considerable importance to the commercial fisheries off the western
Cape and South West African coasts. Research on the biology of this species
has continued since its initiation by D. H. Davies in the 1950s. This research has
been intensified since September 1970 with the commencement of the Cape

*Present address: Sea Fisheries Branch, Cape Town.
125

Ann. S. Afr. Mus. 72 (7), 1976: 125-145, 11 figs, 3 tables.

126 ANNALS OF THE SOUTH AFRICAN MUSEUM

Cross Programme (Cram & Visser 1972) which was instigated by the decline
of the South West African pelagic fishing industry in 1968. The South West
African Pelagic Egg and Larval Survey (SWAPELS), forming part of the Cape
Cross Programme, was started in September 1972. The purpose of this
SWAPELS programme was that of stock assessment of the pilchard and anchovy
by means of an intensive quantitative egg and larva survey off the South West
African coast. A prerequisite of this type of work is accurate identification
of the larvae concerned, based on adequate descriptions of the larvae at all
stages of their development so that pilchard and anchovy larvae can be readily
distinguished from one another, and also from any other clupeid-type larvae
which may occur in the area. It has thus been decided to present detailed descrip-
tions of the development of the pilchard, Sardinops ocellata, and the anchovy,
Engraulis capensis, as and when sufficient larval material of the two species
becomes available. In addition, in western Cape waters, the larvae of the red-eye
sardine, Etrumeus teres, are found in considerable numbers, and their similarity
to the larvae of Sardinops ocellata and Engraulis capensis necessitates a detailed
description of the larvae of Etrumeus teres. At present, however, the available
material lacks certain stages of Engraulis capensis and Etrumeus teres. Conse-
quently the present paper deals only with the development of Sardinops
ocellata.

Some confusion exists in the taxonomy of Sardinops Hubbs, whichis generally
accepted as comprising five species, viz. S. caerulea (California), S. sagax (South
America), S. neopilchardus (New Zealand and Australia), S. melanosticta
(Japan) and S. ocellata (southern Africa). This distinction is followed for the
purposes of this paper, although the authors are aware of Svetovidov’s (1952:
193) classification which places all these as sub-species of Sardinops
sagax.

Because of their importance in the commercial fisheries of the world, con-
siderable interest has been shown in the biology of these species, including
studies of their egg and larval development. Scofield (1934), Ahlstrom (1943)
and Miller (1952) have considered the development of S. caerulea; Uchida (1958)
described the eggs, larvae and juvenile stages of S. melanosticta; Baker (1972)
included the eggs and larval stages in his study of the biology of S. neopilchardus ;
Hart & Marshall (1951) recorded larvae of S. ocellata off the South West
African coast and Davies (1954) described the eggs and larvae of this species
from Cape waters.

Davies (1954) obtained the early larval stages of S. ocellata by hatching
fertilized eggs collected in plankton nets, and later stages directly from plankton
samples. He pointed out that the most important diagnostic feature of the
larvae is the characteristic pigmentation and described briefly the yolk-sac,
larval and juvenile stages mainly in respect of their pigment pattern and the
development of the fins. As has already been pointed out, it was found necessary
to describe the development in greater detail to ensure reliable identification
and separation from the larvae of Engraulis capensis and Etrumeus teres.

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA 7,

MATERIAL AND METHODS

Figure | shows the area off the South West African coast where pilchard
larvae were collected between August and December 1972, at the start of the
SWAPELS programme. Material was obtained by the R.S. Sardinops of the
Sea Fisheries Branch, in monthly plankton samples at fixed stations between
Cape Frio and Hollam’s Bird Island. A detailed description of SWAPELS
methods is given by King & Robertson (1973). Bongo nets of 57 cm and 18 cm
diameters, with mesh sizes of 0,940 mm and 0,300 mm respectively, were fished
in oblique tows from the surface to a depth of 50 metres at each station. Pilchard
larvae sorted from the plankton were preserved in 5 per cent formalin. Yolk-sac
larvae were not obtained in the plankton hauls, but information regarding
these early stages was obtained by hatching, in the laboratory, fertilized pilchard
eggs taken at sea and identified from the descriptions of Sardinops eggs (Davies
1954; Baker 1972). The larvae reared in the laboratory did not survive beyond
the yolk-sac stage.

A total of 164 larval and juvenile specimens from the study area were
examined in detail for pigmentation, fin development, fin position relative to
myotomes (and relative to vertebrae in metamorphosing and early juvenile
specimens) and changes in body proportions during development. Juvenile
material was supplemented by specimens from Cape waters in order to document
the development of scale cover.

In each specimen fin rays were counted and, in addition, the total number
of myotomes, the number of myotomes from cleithrum to pelvic fin, cleithrum
to dorsal fin, cleithrum to anal fin and end of dorsal fin to the origin of the anal
fin were determined. Myotome counts were made from the first complete
myotome behind the cleithrum to the myotome immediately preceding the fin
concerned, this being taken at the extreme dorsal portion of the myotome in
the case of the dorsal fin and the extreme ventral portion in the case of the anal
and pelvic fins. However, since most earlier studies on clupeid larvae (e.g.
Ford 1930) cleared larval specimens and stained bones using alizarin in order
to relate fin position to vertebrae, 24 specimens between 18,8 mm s.l. and 38,58
mm s.l. were cleared and stained (Hollister 1934) so that fin movements at
metamorphosis in S. ocellata could be compared with the changes described for
other species during this stage of development.

Measurements of head length, eye diameter, snout length, body depth
(at the base of the pectoral fin) and lengths to dorsal, anal and pelvic fins were
related to standard length. In considering metamorphosis of the larvae it was
found that measurements from snout to dorsal and anal fins (as used by Lebour
1921 and Baker 1972) did not reflect clearly the changes in fin position
evident in myotome (and vertebral) counts. This was found to be attributable
to the increased rate of head growth and therefore measurements between the
cleithrum and dorsal fin and cleithrum and anal fin were used instead. The
measurements in the figures refer to standard length.

128 ANNALS OF THE SOUTH AFRICAN MUSEUM

. Cape Frio

Rocky Point

_ SOUTH WEST AFRICA

a Palgrave Point

\.Ca pe Cross

\, Hollams Bird Is

Fig. 1. Map of South West African coast, showing the grid (small dots) of the SWAPELS
programme. Large dots indicate stations at which Sardinops ocellata larvae were obtained.

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA 129

GENERAL DESCRIPTION

Sardinops ocellata larvae pass through three stages of development after
hatching and before attaining the juvenile stage. These stages are the yolk-sac
stage which may be regarded as a continuation of embryonic development
subsequent to hatching; the larval stage; and the metamorphic stage when the
larvae undergo changes and begin to acquire characteristics of the adult. The
juvenile stage is that in which the fish possess all the basic adult characteristics.

YOLK-SAC STAGE LARVAE (Figs 2-3)

The newly hatched larvae of S. ocellata are 2,75—2,95 mm in length. The
head, with unpigmented eyes and undeveloped mouth, is flexed downward
over the prominent yolk-sac. This yolk-sac is segmented and has a single
spherical oil globule which is posterior in position. Both yolk-sac and oil globule
are devoid of pigmentation. The yolk-sac measures 0,8 x 0,6 mm in the newly
hatched stages but diminishes in size with utilization of the yolk material.
The dorsal, caudal and anal fin folds are broad and continuous at this stage,
and the anus is situated closer to the posterior end of the body than to the head.
The distance from snout to anus is 82-87 per cent of notochordal length in
newly hatched larvae.

Even in newly hatched larvae most myotomes (44-47) are clearly defined
and only the most posterior ones are not very distinct. The end of the vertebral
column is straight. Pigmentation in newly hatched S. oce/lata 1s typical of
Sardinops, and indeed of most clupeid larvae (Lebour 1921; Miller 1952;
Orton 1953; Baker 1972) in that it consists of a few scattered melanophores on
the dorsal surface of the head and a row of expanded, finely branched melano-
phores on either side of the dorsal fin fold (Fig. 2A). During the period of
utilization of the yolk-sac this dorsal pigmentation migrates ventrally as illus-
trated in Figure 2B. The melanophores in the posterior part of the body are
the first to complete the ventral migration (Fig. 3A), and this trend continues
anteriorly until all the melanophores, except those on the head, have attained
the ventral position (Fig. 3B).

Soon after the end of pigment migration the arrangement of the melano-
phores is as follows:

(1) a few scattered melanophores on the dorsal surface of the head;

(11) a single large melanophore at the base of the pectoral fin;

(111) two (or occasionally three) elongated melanophores mid-ventrally,
anterior to the pectoral fin;

(iv) six to seven pairs of slightly elongated melanophores along the dorsal
edge of the anterior half of the gut, i.e. along the ventral edges of the
myotomes, on either side of the body;

(v) a double row of four to five alternating pairs of elongate melanophores
along the ventral surface of the gut, extending from the position of the
swim-bladder posteriorly, to the anus.

ANNALS OF THE SOUTH AFRICAN MUSEUM

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132 ANNALS OF THE SOUTH AFRICAN MUSEUM

(vi) a few (4-5) small melanophores along the ventral edge of the myotomes,
above the posterior part of the gut (these melanophores are not super-
ficial, but visible through the muscle tissue of the myotomes);

(vii) a single very prominent melanophore on the dorsal part of the gut, in
the position where the gut curves ventrally to the anus; and

(viii) two groups of melanophores situated mid-ventrally along the tail region
of the body, 4-5 lying just dorsal to the base of the anal fin (once this is
developed) and 5-7 close to the tip of the tail and associated with the
caudal lepidotrichia once these are formed.’

A small pectoral bud develops in larvae of about three days and length
4.0 mm and the first pigmentation of the eye commences a little later, at 5,0 mm
notochordal length (n.l.). By the time of completion of pigment migration
(6-day-old larvae, 5,1 mm nl.) the yolk-sac is almost entirely used up and the
head is no longer flexed. Up to this stage the gut is simple, comprising a long
narrow tube which, towards the end of the yolk-sac stage, becomes slightly
wider over its posterior half. Mid-way along the gut and in the position of the
17th-18th myotomes a small inconspicuous swim-bladder is formed.

The pectoral fins also show a slight further development by the end of the
yolk-sac stage in that they are no longer only minute buds but have well-formed
blades. The dorsal, caudal and ventral fin folds are still fairly broad and con-
tinuous at this stage, with a slight constriction just before the caudal region,
especially in the dorsal fin fold. The caudal fin fold is the only region to have
developed lepidotrichia at this stage. At the end of the yolk-sac stage all myo-
tomes are visible and number between 48 and 50, with 38 to 40 myotomes
preceding the anus.

LARVAE (Fig. 4)

The end of yolk-sac utilization marks the beginning of a period of larval
development (5,5 mm n.].-22 mm s.].) during which the major changes taking
place are in body shape and gradual fin formation. The body becomes elongated,
the larvae having a characteristic very slender appearance. The continuous fin
fold which was broad during the yolk-sac stage diminishes progressively and
has marked constrictions before the caudal region. The ventral fin fold, anterior
to the anus, becomes obliterated with the increased development of the gut,
presumably coincidental with the commencement of feeding in the larvae.

The gut is narrow and straight in the anterior region, curving slightly
ventrally for a short distance in the mid-body region, below the swim-bladder.
Posterior to the swim-bladder the gut is wider in diameter and the wall is thicker
than in the anterior part. Some authors (e.g. Baker 1972) have described this
posterior region of the gut as a convoluted tube. Examination and dissection
of the gut in this region have shown, however, that in S. ocellata the gut is in
fact a straight tube with the wall slightly constricted at close and regular inter-
vals. Corresponding to these constrictions are thickened areas of the wall which
protrude into the lumen of the gut. These projections presumably form what

138

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA

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134 ANNALS OF THE SOUTH AFRICAN MUSEUM

D’Ancona (1931) referred to as the spiral valve of the posterior intestine of
larval clupeids. These thickened areas give the gut a striated appearance which
we believe has led some authors to regard the gut as convoluted.

In larvae of S. ocellata the head is slightly elongated and the snout pointed.
This snout is 3,5—4,6 per cent standard length (s.].) and slightly longer than the
diameter of the eye. The post-orbital distance (posterior edge of the eye to the
cleithrum) is greater than the snout length. The bones of the head (not described
here in any detail) are thin and the lobes of the brain are clearly visible through
them. The jaws are well formed from an early stage (5-6 mm n.1.) and in larvae
from about 15 mm s.l. the maxilla reaches to the anterior third of the eye.
A pair of nostrils, with a complex internal structure, is clearly visible in larval
stages and becomes increasingly developed through to the juvenile stage.

Flexion of the notochord occurs between 7,4 mm n.l. and 11,3 mm s.l.
Fin development progresses fairly rapidly in the larvae from about 9,0 mm s.1.,
when the first rays appear in the dorsal fin fold followed by the first caudal rays
at 10,5 mm s.l. and the first anal rays at 11,5 mm s.I. Prior to this only lepido-
trichia were present in the unpaired fins and in the pectorals. The latter, however,
do not advance beyond this condition, apart from an increase in size, until late
in larval life. Subsequent development of the dorsal and anal fins proceeds
apace until 16-17 rays are present in each fin prior to the commencement of
metamorphosis of the larvae at 22 mm s.]. Additional rays ossify in the anterior
regions of these fins during metamorphosis so that the full complement of
dorsal rays (18-20) is reached by 26 mm s.]. and the anal is complete with
18-20 rays by 29 mm s.]. The last dorsal and anal rays are double from about
19 mm s.l., and, in addition, the second last anal ray is very deeply branched
(almost from its base). The last two anal rays are slightly elongated and form a
‘finlet’ which is characteristic of Sardinops (Svetovidov 1952: 189). Ossification
of the caudal rays which commenced at 10,5 mm s.l. progresses rapidly so
that by 13,0 mm s.l. 13-15 rays are visible, although not completely developed.
At this stage the ventral part of the caudal fin is more advanced than the dorsal
part. By 18,1 mm s.1. (Fig. 4B) all 19 primary caudal rays are formed, and some
of them are slightly branched. Some secondary rays are also present. By 20,0 mm
s.l. the branching of the 17 inner primary caudal rays is appreciable and from
23,0 mm s.]. the caudal fin rapidly assumes its deeply forked shape (Fig. 5A).
The pelvic fin appears as a small bud at 18,0 mm s.]. and its first rays start to
develop at 22-23 mm s.|. The pelvic fin with its full complement of 8 rays, of
which all except the anterior ones are branched, is fully formed by 26,0 mm s.1.
The pectoral fin, in which lepidotrichia formed at a very early stage, is the last
of the fins to complete development. The fin rays form only from 23,0 mm s.l.,
although these are then laid down rapidly so that 15-16 are present by 29 mm
s.l. and the full complement of 18 rays is reached by 33 mm s.1. Details of fin
ray development in the paired and unpaired fins are given in Table 1.

As is evident from Figure 4A—C little change occurs in the general appear-
ance of the larvae after the end of the yolk-sac stage until 20-22 mm s.l., apart

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA 135

TABLE |

Development of fin rays in S. ocellata larvae between 8 mm and 33 mm standard length

Size range Mean Dorsal Anal Pectoral Pelvic
(mm) (mm) No. rays rays Caudal rays rays rays
8,0— 8,9 8,90 1 5-6 t ii t ==
9,0— 9,9 YS) 2 9 t fi t =

10,0-10,9 10,40 4 9-12 0- 4 T i =
11,0-11,9 11,65 6 10-14 5- 8 5-9 ii =
12,0-12,9 12253 7 10-14 7-9 12-15 i =
13,0-13,9 13,45 22 11-16 8-10 13-15 t =
14,0-14,9 14,41 12 12-16 10-13 15-17 t =
15,0-15,9 15,61 9 13-16 13-15 16-18 ==
16,0-16,9 16,18 1 15 13 18 =
17,0-17,9 17,50 2 Eyer. 14-16 18-19 —
18,0-18,9 18,51 9 15-16 15-17 $#+ 19 +4 t bud
19,0-19,9 19,53 15 15-17 15-17 1+ 19 $ bud
20,0-20,9 20,27 8 16-17 15-17 Poe NEN el bud
21,0-21,9 21,60 3 16-17 15-17 2+ 19 +1 bud
22,0-22,9 ns 0 — ~- ao — —

23,0-23,9 23,41 3 17-18 17 ae Oy Bey 3-5 4-5

24,0-24,9 24,70 3 18 NY 5-+- 19. +4 6-8 6-7

25,0-25,9 25,06 1 18 17 Se Me Wee i 7

26,0-26,9 26,29 2 18-20 17-18 6S) 190-5 10-12 8

27,0-27,9 DOT 1 19 17 64-7 19° 525 11 8

28,0-28,9 28,58 1 20 17 7+ 19 +45 15 8

29,0-29,9 29,59 3} 19-20 18-20 Sep LOT 15-16 8

30,0-30,9 30,97 1 20 18 8+ 19 +7 17 8

31,0-31,9 31533 D} 19-20 19-20 8+ 19 47 iL 8

32,0-32,9 — 0 —- — -- = —

33,0-33,9 33,67 2 18-19 19-20 Jae WE Sea 18 8

+ indicates lepidotrichia present, but no rays.

Caudal fin counts, from 18 mm s.]. are preceded and followed by additional counts; these
indicate the number of secondary caudal rays on the dorsal and ventral parts of the caudal fin
respectively.

from the fin development described above. The dorsal and anal fins are situated
far posteriorly on the long slender larvae. The origin of the dorsal fin occurs
above the 29th myotome when thickening first appears in the dorsal fin fold,
but lies over myotomes 23-26 once the dorsal fin nears completion, since the
anterior rays are the last to develop. The anal fin origin lies below 39-41 in
very young larvae and below myotomes 36-38 in older larvae. The end of the
dorsal fin and origin of the anal fin are separated by 6-8 myotomes. At the time
when the pelvic fin first forms it occupies a position corresponding to the 15th,
16th or 17th myotome, and is situated well in front of the origin of the dorsal
fin. The pelvic fin and the origin of the dorsal fin are separated by 8-10 myo-
tomes prior to metamorphosis.

The pattern of pigmentation of the larvae shows little change during
larval development and remains basically that attained at the end of the yolk-
sac stage. However, there is an increase in the number of melanophores con-
tributing to this pattern. The 6-7 pairs of elongate melanophores along the
ventral edge of the myotomes, adjacent to the anterior half of the gut increase

136 ANNALS OF THE SOUTH AFRICAN MUSEUM

to 9-11 pairs at 11 mm s.]. and become even more numerous, but less elongate,
at the end of the larval stage (Fig. 4C). There is a similar increase in the number
of mid-ventral melanophores on the posterior half of the gut and the number
of embedded melanophores above the posterior half of the gut increases to
10 pairs at 11 mmss.]. and there are as many as 17 pairs of these melanophores
at 23 mm s.l. with additional smaller melanophores scattered in between them.
Moreover, at the end of the larval stage, there is some pigmentation of the
caudal fin. This comprises melanophores formed along the edges of the rays
and arranged to form transverse rows, parallel to the outline of the caudal
fin (Fig. 4C). A few melanophores also develop on the proximal radials of the
dorsal fin base. From 17-18 mm s.]. a few isolated melanophores appear mid-
laterally along the body and these gradually become more numerous. From the
time the pelvic rays commence development there is usually a single large
melanophore just anterior to the base of the pelvic fin.

METAMORPHIC STAGE LARVAE (Fig. 5A)

From 22 mm s.]. the larvae of S. ocellata undergo marked changes in body
proportions and pigmentation, which result in larvae of 22-32 mm s.l. being
termed metamorphic stage larvae. The various body proportions which were
studied for the complete developmental series are illustrated in Figures 6-10.
These graphs show that the body proportions all remain constant relative to
standard length until the larvae attain the size of 22 mm s.l., at which stage
changes in body depth, head length and in the position of the dorsal, anal and
pelvic fins commence. Some of these characters show further changes at 33-36
mm s.I., thus indicating the final transition to the juvenile condition.

The onset of metamorphosis is indicated by changes in head growth and
body depth and in the commencement of the ventral growth of the myotomes.
During the larval stage the head length increases constantly in relation to the
standard length. At the start of metamorphosis, however, the rate of increase
of the head length accelerates (Fig. 6). The increase in body depth (measured
as depth at the pectoral base) follows the pattern of change in head growth but
to a more marked degree (Fig. 7). In addition to this overall increase in body
depth in larvae of more than 22 mm s.l., it may be seen from Figure 4C that
the myotomes at this stage start to grow ventrally so that they begin to cover
the gut. At 23 mm s.l. the myotomes merely obscure the dorsal edge of the gut,
but their expansion becomes more marked, first over the anterior half of the
gut and later extending also over the posterior half of the gut, so that by 29,5 mm
s.l. the gut is almost entirely covered by myotome tissue, except for a small
area Close to the anus. At this stage, however, they have not yet fused ventrally.
In larvae of 30-31 mm s.]. most myotomes anterior to the pelvic fins are fused
mid-ventrally and the first two or three scutes have developed in the most
anterior mid-ventral region.

In common with the development of other clupeids, one of the most
marked features of metamorphosis in S. oce/lata is the alteration in the position

137

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA

‘uoleusWsId [esIop Jo JUNOWIL
9]qRAIPISUOD B puv dJo/CWOS UONRASIW UY YUM o8e}s ofluoAnf AjIeg “gq “suoIsod uy ul UOIeJOI]e SUIMOYS VAIL] O3v}S 1YdIOWRIZJ, “YW “¢ ‘SI

WwW 7'ZZ

Head Length (mm)

138 ANNALS OF THE SOUTH AFRICAN MUSEUM

of the dorsal and anal fins which occurs during this stage. Instead of the steady
rate of increase shown in the distances from cleithrum to dorsal fin and cleithrum
to anal fin (Figs 8-9) during the larval stage, metamorphic stage larvae show a
slight decrease in cleithrum to dorsal fin distance and only a very slight con-
tinued increase in cleithrum to anal fin distance. These changes in the pattern
of growth occur in larvae of 24-33 mm s.|. They can be attributed to the anterior
migration of the dorsal and anal fins, relative to myotomes and vertebrae. Most
authors (Lebour 1921; Ford 1930; Ahlstrom 1943, 1968) documented fin
migration relative to vertebrae, but others (Schnakenbeck 1929; Baker 1972)
used myotomes. Attempts to stain vertebrae in specimens 18-20 mm s.l. were
not satisfactory as the most anterior vertebrae did not take up the alizarin dye,
although older stages stained satisfactorily. This precluded the determination
of fin position relative to vertebrae in pre-metamorphic larvae. For this reason
fin position relative to myotomes was used as this could be determined through-

8 . @
6
.

%

AE
| Pe
24 at
i
it iii 2 i ioe i= 25>

Standard Length (mm)

Fig. 6. Graph of increase in head length with increase in standard length. Note acceleration
of head growth from 22 mm s.1.

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA 139

Depth at Pectoral Base (mm)

10 20 40 50 60

30
Standard Length (mm)

Fig. 7. Graph of body depth (as depth at pectoral base) versus standard length. Initial decrease
(2-5 mm s.l.) is due to yolk-sac utilization. Note increased rate of deepening of body from
23 mm s.1.

Cleithrum to Dorsal Fin

Standard Length (mm)

Fig. 8. Graph of distance from cleithrum to dorsal fin versus standard length, showing a
decrease during the phase of anterior migration of the dorsal fin.

140 ANNALS OF THE SOUTH AFRICAN MUSEUM

out development. However, to permit comparison of fin migration in S. ocellata
with that which occurs in other species of Sardinops, fin positions relative to
vertebrae in late larval and metamorphic stages are given in Table 2. Some
differences in counts (usually of 1-3) are evident between the two methods and
these differences can be attributed to two factors. Firstly, only complete myo-
tomes posterior to the cleithrum were counted and this omits 1-2 incomplete
myotomes at the anterior region of the body. Secondly, vertebral counts were
taken at positions vertically below or above the fins concerned, but myotome
counts at dorsal and ventral edges adjacent to the fin origins. The <-shape of
the myotomes makes a further difference of 1-2 in the counts as the anterior
region of the myotome corresponds to a vertebral centrum |-2 centra anterior
to the one below the posterior part of the myotome. (This difference is slightly
greater in older specimens, e.g. 38,58 mm juvenile.) However, as the two methods
reflect similar changes during metamorphosis, myotome counts can be accepted
as a reliable method of documenting fin migration.

TABLE 2

Fin position relative to myotome (M) and vertebral (V) counts
in late larval and metamorphic stages of S. ocellata.

Standard
Length Dorsal Fin Anal Fin Pelvic Fin
(mm) M V M V M V
18,80 25 — 38 — —_— —
19,00 24 — 37 — —_ —
19,22 25 — 38 17 —
19,63 24 26 37 39 16 18
19,71 24 — 37 — 15 —
19,87 25526 ay) 3S) Se
19,96 24 — 36 — 15 —
20,54 24 — 38 16 —
20,70 23 — 38 — 15 —
21,68 22. 24 36 «38 Seley
23,16 237 25 36 38 16 18
24,64 22, 24 36 638 NG 17
24,64 DD DA 36 638 1S ssaetl7
24,81 23 26 36 639 16 18
25,06 2 25 35) 38 NS l7/
26,29 2) 24 sy 3i1/ WG. 7
26,29 Die28 815) S30/ ey 9/
28,58 19 22 34 36 16 18
29,56 19 22 313} = 36 17 18
29,56 ls} 115) 33 36 16 18
29,64 Oe 22 335536 Lg alts}
30,97 ie 9, 313} - 36 IS) 7
31,20 14 17 31 34 Ne iS)
38,58 13 7 SileS6 16 20

(mm)

Fin

Cleithrum to Anal

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA 141

As is evident from Figure 11 the number of myotomes preceding the dorsal
fin (open triangles) is 22—25 in larvae of 20-23 mm s.1., but from 24 mm s.]. the
number decreases sharply due to the forward migration of the fin. This con-
tinues until the fin reaches the position of myotomes 10-13 at 33-35 mm s.].
Migration of the dorsal fin ceases at this size, having covered the extent of 10-12
myotomes. Migration of the anal fin (Fig. 11—closed triangles) is not as exten-
sive as that of the dorsal fin, but nevertheless is quite considerable. The origin
of the anal fin shifts from the position of myotomes 36-38 at 20-25 mm s.l.,
to reach myotome 31 at 31-33 mm s.1.—thus involving a shift over 5-7 myo-
tomes. At the end of migration the end of the dorsal fin and the origin of the
anal fin are separated by five myotomes. Once the larvae attain the size of
33-35 mm s.l. the increases in the distances from cleithrum to dorsal fin and
cleithrum to anal fin resume their pre-metamorphic rates (Figs 8-9). This can
be regarded as an indication of the end of the metamorphic stage and the attain-
ment of the juvenile stage.

During metamorphosis the rate of increase in distance from cleithrum to
pelvic fin diminishes for a short growth interval (23-26 mm s.I.) (Fig. 10). This
cannot be explained by any forward shift in pelvic fin position relative to myo-
tomes as the fin retains its position at myotomes 15-17 (or vertebrae 17-18)
as in the late larval stages when the pelvic bud first appeared. However, later
in development the pelvic fin shifts posteriorly relative to vertebrae (but not
relative to myotomes) and comes to lie vertically below vertebrae 19-20. With
the migrations of the dorsal and pelvic fins, their positions relative to one

cen!
aes
Pal 4
10 do : 30 / 40 u 50 z ab

Standard Length (mm)

Fig. 9. Graph of distance from cleithrum to anal fin versus standard length, showing reduction
in rate of increase whilst anal fin undergoes anterior migration between 23 mm and 33 mm s.1.

142 ANNALS OF THE SOUTH AFRICAN MUSEUM

=
=
=
Le
©
2
&
je)
2
£
=)
—_
ks
=
a)
S)
20 30 40 50 60
Standard Length (mm)
Fig. 10. Graph of distance from cleithrum to pelvic fin versus standard length.
-
aA
40-| Ah Ab AbA aA Bb ed
ms Pore swe we Sy a a
ba AA A mmAs dA
4 samme 4 a
a ae AA
4 aa fk Re .
aA
aa a a a a
304
Pe aay 444 a aa
a 44 44644
a ASS Ares A a
Ada sayy a
Pavars¥orswavan ay a
Faravavesvec ay
a4 44 a
4 44
A 4A
20
a
4
a
a A
A a
10 a a
a
T es a ied ee ee Sa
aa to 20. r 30 do 50 60

Standard Length (mm)

Fig. 11. Graph of the number of myotomes from cleithrum to anal fin (closed triangles) and

cleithrum to dorsal fin (open triangles) indicating the anterior migration of the fins from

23 mm s.]. The gradual decrease in number of myotomes to 23 mm s.1. is due to development
of additional fin rays.

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA 143

another alter and instead of the pelvic fin lying anterior to the dorsal origin,
it lies vertically below the dorsal origin at 27-29 mm s.l. and by 32-33 mm s.1.
the pelvic origin corresponds to a position below the middle of the base of the
dorsal fin as is the case in adults of the species.

Throughout the larval stage both pectoral and pelvic fins lack ossified
rays. Ossification of rays in the paired fins commences in larvae over 22 mm s.L.,
i.e. at the onset of the metamorphic stage. By the time the juvenile stage is
reached fin ray development is complete in paired and unpaired fins (Table 1).

Pigmentation also changes quite markedly during the metamorphic stage.
With the ventral growth of the myotomes, much of the larval pigment pattern
near the gut is obliterated or lost. It is replaced by pigment spots which form
beneath the myotomes, along the dorsal surface of the gut (? on the peritoneum)
and which are partially visible through the myotomes. The melanophores which
first appeared in larvae of 17-18 mm s.]. along the mid-lateral sides of the body,
become far more numerous, especially from 25-26 mm s.|., so that the larvae
develop a fairly dark mid-lateral band of pigment (Fig. 5A). Furthermore, a
large number of melanophores appears along the dorsal surface of the body.
These are stellate melanophores and are arranged in lines which follow closely
the edges of the myotomes, with a few melanophores scattered in between.
In spite of the appearance of this quite considerable amount of pigment on the
dorsal surface of the body, which might be considered an approach towards
the adult coloration, larvae of 30-32 mm s.l. are still predominantly pale, as
were the earlier larvae. Pigmentation on the head also increases, particularly
on the dorsal surface of the head, in the region of the parietals, and there are
scattered melanophores on the opercular and circumorbital bones.

Scale development commences towards the end of the metamorphic stage.
Since few specimens of 30-45 mm s.I. were available from the main study area,
the material was supplemented with specimens of that size range used in the
study by Davies (1954) and the 1950-67 egg and larval survey in Cape waters
(Haigh 1972: 49, 66, fig. 9). Scales are first formed at 30 mm s.]. These develop
on the caudal peduncle and are arranged in an anteriorly pointing ‘V’ pattern.
The scale-covered area enlarges rapidly so that it reaches the area above the
anal fin by 31,5 mm s.I. and by 33 mm s.l. all of the body posterior to the mid-
region of the dorsal fin base is covered. By 36 mm s.I. scale cover reaches
anteriorly to the cleithrum, but anterior to the dorsal fin the scales do not
overlap. Scale development is completed early in the juvenile stage.

JUVENILE STAGE (Fig. 5B)

The juvenile stage is that in which the metamorphic changes are complete
and the young fish resembles the adult. As can be seen from Figure 5B the
juvenile fish resembles the adult in shape; in addition to the pigment which
appeared during metamorphosis, the dorsal part of the body is covered with
small closely arranged melanophores, which give the fish the dark dorsal and
light ventral appearance of the adult; the head is extensively pigmented, and

144 ANNALS OF THE SOUTH AFRICAN MUSEUM

on the opercular bones the radial ridges are clearly visible; the entire body is
covered with scales and ventral scutes are present anterior to and behind the
pelvic fins; the last two anal rays are distinctly longer than the more anterior
rays, and the pelvic and pectoral fins are well developed.

As juvenile development proceeds pigmentation on the dorsal area of the
body increases further, and silvery pigment develops on the lateral and ventral
parts of the body from about 37 mm s.]. and the row of dark pigment spots
which is characteristic of adult pigmentation forms from 45 mm s.].

DISCUSSION

In yolk-sac and larval stages of development Sardinops ocellata follows
closely the pattern of development described for S. caerulea (Miller 1952),
S. neopilchardus (Baker 1972) and S. melanosticta (Uchida 1958). However,
it is evident that some differences do occur in the development of these species,
during the later phases of larval life. These differences are in the number of
myotomes or vertebrae over which the fins migrate and also the relative sizes
at which the changes occur. These differences are summarized in Table 3.

TABLE 3

Comparison of late stages of development in species of Sardinops

ocellata caerulea neopilchardus — melanosticta
(Ahlstrom (Baker (Uchida
1968) 1972) 1958*)
Posterior migrationof pelvicfins 2 vertebrae 3 vertebrae 5 myotomes ?
Final position of pelvic fins . 18—20th 22nd 22nd
vertebrae vertebra myotome u
Anterior migration of dorsal fin 10-12 10 10-12
myotomes vertebrae myotomes i
Final position of dorsal fin . 10-13th 18th 14-16th
myotomes vertebra myotomes ?
Metamorphic stage. : . 22-32 mm 25-40 mm 25-35 mm ? 30-40 mm
Sil: s.l. Salk sal
Juvenile : ; : : . 33 mms.l. 40 mm s.l. 35 mm s.]. ? 42 mm s.l.

* Text in Japanese, information from figures and legends only.

ACKNOWLEDGEMENTS

The authors would like to express their thanks to the Sea Fisheries Branch,
Walvis Bay (E.L.) and the South African Museum (M.J.O’T.) for the
co-operation of these institutions during visits in the course of this study.
Thanks also to Dr N. A. H. Millard and Miss M. A. Roeleveld for their helpful
criticisms of the manuscript.

LARVAL DEVELOPMENT OF SARDINOPS OCELLATA 145

REFERENCES

AHLSTROM, E. H. 1943. Studies on the Pacific sardine or pilchard (Sardinops caerulea). 4.
Influence of temperature on the rate of development of pilchard eggs in nature. — Fish.
Bull. U.S. Spec. Sci. Rep. 23: 1-26.

Autstrom, E. H. 1968. Review— Development of fishes of the Chesapeake Bay region, An
atlas of eggs, larval and juvenile stages, Part I.— Copeia 1968 (3): 648-651.

Baker, A. N. 1972. Reproduction, early life history and age-growth relationships of the
New Zealand pilchard, Sardinops neopilchardus (Steindachner).— Fish. Res. Bull. N.Z. 5:
1-64.

Cram, D. L. & VISsER, G. A. 1972. Cape Cross research programme— Phase Il —A summary
of results.—S. Afr. Shipp. News Fish. Ind. Rev. 27: 40-43.

D’Ancona, U. 1931. Uova, larve e stadi giovanili di Teleostei . . . Famiglia 1: Clupeidae.
—Fauna e Flora del Golfo di Napoli 38 (1): 1-16.

Davies, D. H. 1954. The South African pilchard (Sardinops ocellata). Development, occurrence
and distribution of eggs and larvae, 1950—-51.—Jnvestl. Rep. Div. Sea Fish. Un. S. Afr. 15:
1-28.

Forp, E. 1930. Herring investigations at Plymouth. VIII. The transition from larva to ado-
lescent.—J. mar. biol. Ass. U.K. 16: 723-752.

HaiGuH, E. H. 1972. Larval development of three species of economically important South
African fishes.—Ann. S. Afr. Mus. 59: 47-70.

Hart, T. J. & MARSHALL, N. B. 1951. Breeding ground of pilchards off the coast of South-
West Africa.— Nature, Lond. 168: 272-273.

HO .uisTer, G. 1934. Clearing and dyeing fish for bone study.— Zoologica, N.Y. 12: 89-101.

Kina, D. P. & Rosertson, A. A. 1973. Methods of pelagic fish egg and larval research in
South West Africa.—S. Afr. Shipp. News Fish. Ind. Rev. 28: 57-61.

Lepour, M. V. 1921. The larval and post-larval stages of pilchard, sprat and herring from
Plymouth district.—J. mar. biol. Ass. U.K. 12: 427-457.

Miter, D. J. 1952. Development through the prolarval stage of artificially fertilized eggs of
the Pacific sardine (Sardinops caerulea).— Calif. Fish Game 38: 587-595.

Orton, G. L. 1953. Development and migration of pigment cells in some teleost fishes.
—J. Morph. 93: 69-99.

SCHNAKENBECK, W. 1929. Entwicklungsgeschichtliche und morphologische Untersuchungen
am Hering.— Ber. dt. wiss. Kommn Meeresforsch. (N.F.) 5: 19-77.

SCOFIELD, E. C. 1934. Early life history of the California sardine (Sardina caerulea) with special
reference to the distribution of eggs and larvae.— Fish. Bull Calif. 41: 1-48.

Svetovipoy, A. N. 1952. Fauna of U.S.S.R. Fishes. Vol. Il No. 1: Clupeidae.— Opred. Faune
S.S.S.R. (n.s.) 48 (2, no. 1): 1-331. (Translated from Russian.)

Ucuipa, K. 1958. Eggs, larvae and juvenile of Sardinops melanosticta (Temminck & Schlegel)
(Clupeidae). In: Ucuipa, K. et al. Studies on the eggs, larvae and juvenile of Japanese
fishes. Series 1. Fukuoka: Second Laboratory of Fisheries Biology, Fisheries Department,
Kyushu University.

mn

ieee

6. SYSTEMATIC papers must conform with the International code of zoological nomenclature
(particularly Articles 22 and 51).

Names of new taxa, combinations, synonyms, etc., when used for the first time, must be
followed by the appropriate Latin (not English) abbreviation, e.g. gen. nov., sp. nov., comb.
nov., Syn. nov., etc.

An author’s name when cited must follow the name of the taxon without intervening
punctuation and not be abbreviated; if the year is added, a comma must separate author’s
name and year. The author’s name (and date, if cited) must be placed in parentheses if a
species or subspecies is transferred from its original genus. The name of a subsequent user of
a scientific name must be separated from the scientific name by a colon.

Synonymy arrangement should be according to chronology of names, i.e. all published
scientific names by which the species previously has been designated are listed in chronological
order, with all references to that name following in chronological order, e.g.:

Family Nuculanidae
Nuculana (Lembulus) bicuspidata (Gould, 1845)
Figs 14-15A
Nucula (Leda) bicuspidata Gould, 1845: 37.
Leda plicifera A. Adams, 1856: 50.
Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (figs 8a—b).
Nucula largillierti Philippi, 1861: 87.
Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8-9.

Note punctuation in the above example:
comma separates author’s name and year
semicolon separates more than one reference by the same author
full stop separates references by different authors
figures of plates are enclosed in parentheses to distinguish them from text-figures
dash, not comma, separates consecutive numbers

Synonymy arrangement according to chronology of bibliographic references, whereby
the year is placed in front of each entry, and the synonym repeated in full for each entry, is
not acceptable.

In describing new species, one specimen must be designated as the holotype; other speci-
mens mentioned in the original description are to be designated paratypes; additional material
not regarded as paratypes should be listed separately. The complete data (registration number,
depository, description of specimen, locality, collector, date) of the holotype and paratypes
must be recorded, e.g.:

Holotype
SAM-—A13535 in the South African Museum, Cape Town. Adult female from mid-tide region, King’s Beach,
Port Elizabeth (33°51’S 25°39’E), collected by A. Smith, 15 January 1973.

Note standard form of writing South African Museum registration numbers and date.

7. SPECIAL HOUSE RULES

Capital initial letters

(a) The Figures, Maps and Tables of the paper when referred to in the text
e.g. ‘... the Figure depicting C. namacolus ...’; ‘.. . in C. namacolus (Fig. 10)...’

(b) The prefixes of prefixed surnames in all languages, when used in the text, if not preceded
by initials or full names
e.g. DuToit but A.L.du Toit; Von Huene but F. von Huene

(c) Scientific names, but not their vernacular derivatives
e.g. Therocephalia, but therocephalian

Punctuation should be loose, omitting all not strictly necessary

Reference to the author should be expressed in the third person

Roman numerals should be converted to arabic, except when forming part of the title of a
book or article, such as
“Revision of the Crustacea. Part VII. The Amphipoda.’

Specific name must not stand alone, but be preceded by the generic name or its abbreviation
to initial capital letter, provided the same generic name is used consecutively.

Name of new genus or species is not to be included in the title: it should be included in the
abstract, counter to Recommendation 23 of the Code, to meet the requirements of
Biological Abstracts.

“WAND)LNNOONNINN
3 9088 01206 6502

ELIZABETH LOUW & M. J. OTOOLE
LARVAL DEVELOPMENT OF SARDINOPS OCELLATA
(PISCES : CLUPEIDAE)