U5ZX nH Number 486 26 June 2001 Contributions in Science A New Brooding Brittle Star from California (Echinodermata: Ophiuroidea: Amphiurdea) Gordon Hendler and Carla J. Bundrick rM. 0 3 2001 ^ 4^fiARlES Serial Publications ol THE Natural History Museum ol Los Angeles County Scientific Publications Committee John Heyning, Deputy Director for Research and Collections John M. Harris, Committee Chairman Brian V. Brown Kenneth E. Campbell Kirk Fitzhugh Karen Wise K. Victoria Brown, Managing Editor The scientific publications of the Natural History Museum of Los Angeles County have been issued at irregular in- tervals in three major series; the issues in each series are numbered individually, and numbers run consecutively, re- gardless of the subject matter. # Contributions in Science, a miscellaneous series of tech- nical papers describing original research in the life and earth sciences. # Science Bulletin, a miscellaneous series of monographs describing original research in the life and earth sci- ences. This series was discontinued in 1978 with the issue of Numbers 29 and 30; monographs are now published by the Museum in Contributions in Science. # Science Series, long articles and collections of papers on natural history topics. Copies of the publications in these series are sold through the Museum Book Shop. A catalog is available on request. The Museum also publishes Technical Reports, a miscel- laneous series containing information relative to scholarly inquiry and collections but not reporting the results of original research. Issue is authorized by the Museum’s Sci- entific Publications Committee; however, manuscripts do not receive anonymous peer review. Individual Technical Reports may be obtained from the relevant Section of the Museum. Printed at Allen Press, Inc., Lawrence, Kansas ISSN 0459-8113 Natural History Museum of Los Angeles County 900 Exposition Boulevard Los Angeles, California 90007 A New Brooding Brittle Star from California (Echinodermata: Ophiuroidea: Amphiuridae) Gordon Hendler1 and Carla J. Bundrick2 ABSTRACT. Amphiodia akosmos n. sp. is the only Amphiodia species known to bear live young, and like many brooding brittle stars, it is of diminutive size. It is characterized by irregularly arranged opaque disk scales, primary disk plates that are inconspicuous or lacking, wing-shaped middle arm spines, and a single elongate tentacle scale. There is an allometric relationship between arm length and disk diameter. Specimens of different sizes cannot be characterized by a unique ratio of arm length to disk diameter, a complication generally ignored in previous descriptions of ophiuroids. Adult individuals attain approximately 4 mm disk diameter and closely resemble the young of a larger, sympatric species, Amphiodia occidentalis. This sug- gests that A. akosmos is progenetic. However, various of its characteristics may be paedomorphic, pera- morphic, and nonheterochronic in origin. In contrast to female A. occidentalis, which broadcast-spawn thousands of small eggs, A. akosmos individuals hold fewer than 30 yolky eggs, which can reach 430 |xm in diameter. All dissected specimens (N = 8) were female, an indication that the species could be gono- choric, but also that it might be protandric or parthenogenetic. Thus far, the species is known only from the intertidal zone within 200 km of the Monterey Peninsula, California. INTRODUCTION “It is a fabulous place: when the tide is in, a wave- churned basin, creamy with foam, whipped by the combers that roll in from the whistling buoy on the reef. But when the tide goes out the little water world becomes quiet and lovely. The sea is very clear and the bottom becomes fantastic with hur- rying, fighting, feeding, breeding animals. . .” (Steinbeck, 1945) From time to time, an unnamed species of Am- phiodia has been recognized as inhabiting the cen- tral California coast. It is named and described herein, based primarily on specimens collected from the Great Tide Pool, at Point Pinos, on the tip of the Monterey Peninsula, the locality vividly depict- ed in the epigraph. That naming this species has been so long de- layed, despite its having been noted in two editions of Light’s Manual (Weesner, 1954; Sutton, 1975), is indicative of the scant attention that has been directed toward Eastern Pacific ophiuroids. Al- though the first account of the fauna was published over 150 years ago (Muller and Troschel, 1843), Eastern Pacific ophiuroids have never been exten- sively collected, their representation in museums is limited, and the group has not been monographed. The present study is a small step toward correcting that situation. Friedman (1948) may have been the first to no- 1. Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007. Email: hendler@nhm.org 2. 24 Talbot Street, Salinas, California 93901. Contributions in Science, Number 486, pp. 1-11 Natural History Museum of Los Angeles County, 2001 tice the new species. He reported two specimens, which were from Monterey Bay, of Amphiodia with “one broad tentacle scale” and a disk diameter of about 2 mm. Although he mistakenly identified them as a tropical species, his description of the animals suggests that he had found either the new species reported herein, or juvenile individuals of Amphiodia occidentalis (Lyman, 1860). Although some of Friedman’s ophiuroids are deposited at the California Academy of Sciences, these specimens of “ Amphiodia tabogae” are believed lost. The new species was certainly known to Weesner (1954), who differentiated “ Amphiodia sp.” from A. occidentalis in the second edition of Light’s Manual. She distinguished the new species based on its arm/disk ratio and single tentacle scales, and more definitively by its “ovoviviparous” reproduc- tion. Unfortunately, no record exists of where along the central California coast her specimens were col- lected (F. Lechleitner, nee Weesner, personal com- munication). The second author of the present report (under the name Cunningham, 1977) rediscovered the small, brooding Amphiodia species in the course of research on A. occidentalis. She noted additional features distinguishing the two Amphiodia species, in addition to those taxonomic characters cited by Weesner (1954). Specimens that she collected were examined by Sutton (1975) and treated as “Am- phiodia sp.” in the third edition of Light’s Manual. However, as noted below, Sutton evidently con- fused juvenile A. occidentalis and adults of the new species and incorrectly concluded that the new spe- cies “May be a variety of A. occidentalis ” (Sutton, Figure 1 Ampbiodia occidentals , 8.1 mm dd, LACM 1998-089.010 (top), an adult individual of moderate size; Am- phiodia akosmos, 3.5 mm dd, holotype, LACM 1993-035.004 (bottom), a full-grown adult 1975:633). Until this report, nothing further was published on the species, save for references to Cunningham’s observations (Austin and Hadfield, 1980; Rumrill and Pearse, 1985; Hendler, 1991). MATERIALS AND METHODS Standard methodology and terminology were used for the taxonomic analysis. The diameter of the disk (dd) was measured from the outer edge of the radial shields to the opposite edge of the disk. The length of the arm (AL) was measured for the longest arm of an individual, from the edge of the disk to the arm tip. Data were not recorded for specimens with broken or regenerated arms. The AL and dd of a range of sizes of A. occidentals from several localities were measured for comparison with individuals of the new species. The allometric equation, Y = aXb (where Y = AL, X = dd), was used to describe the relationship between arm and disk dimensions. Statistical analysis of the data was based on a Model I regression of the linearized expression, In Y = In a + b in X. Two- tailed Student’s t tests were used to determine the signifi- cance of the regression based on deviation of the corre- lation coefficient from zero, and departure from isometry based on deviation of the regression coefficient (= con- stant of allometry) from unity (Sokal and Rohlf, 1995). The following abbreviations are used in this paper. CASIZ, California Academy of Sciences; LACM, Natural History Museum of Los Angeles County; USNM, Nation- al Museum of Natural History. 2 ■ Contributions in Science, Number 486 SYSTEMATIC ACCOUNT Family Amphiuridae Genus Ampbiodia Merrill, 1899 Ampbiodia ( Ampbiodia ) akosmos new species Figures 1-4 Ampbiodia sp. Weesner, 1954:291; Sutton, 1975: 631, in part; Cunningham, 1977:41. ETYMOLOGY. The specific name, transliterated from the Greek term Lor “unorganized,” refers to the irregular distribution of dorsal disk scales and to the apparent absence of the rosette of primary disk plates that comprise an orderly system (“kos- mos”) in other species of Ampbiodia. MATERIAL EXAMINED. Except as noted, all specimens in the type series are preserved in ethanol and were collected from the intertidal zone in the Great Tide Pool at Point Pinos, Pacific Grove, Mon- terey County, California, located approximately 36° 37.7'N, 121° 56.20'W. Holotype. (LACM 1993-35.4), 24 Jul. 1993, coll. Hendler. Paratypes. (LACM 1976-659.1), 1 spec., brood- ing, 16 Feb. 1976, coll. Bundrick; (LACM 1975- 674.1), 1 spec., 7 Oct. 1975, coll. Bundrick; (LACM 1975-674.2), 1 spec., 7 Oct. 1975, coll. Hendler and Bundrick: New Brooding Brittle Star Figure 2 Dorsal view of the disk and the middle spine on the 10th arm joint from the disk edge of: A, adult Amphiodia akosmos, holotype, LACM 1993-035.004, 3.5 mm dd, spine length 0.28 mm; B, juvenile Amphiodia occidentalis, LACM, 1993-036.007, 3.4 mm dd, spine length 0.32 mm Bundrick; (LACM 1975-675.1), 2 spec., 3 Nov. 1975, coll. Bundrick; (LACM 1993-36.2), 3 spec., 23 July 1993, coll. Hendler and Bundrick; (LACM 1993-036.6), 1 spec., 23 July 1993, coll. Hendler and Bundrick; (LACM 1993-35.1), 2 spec., 24 July 1993, coll. Hendler; (LACM 1999-48.1), 1 spec., 27 Mar. 1999, coll. Bundrick; (USNM E51873), 1 spec., brooding female, 24 Oct. 1999, coll. Bun- drick; (LACM 1999-49.2), 1 spec., female, 24 Oct. 1999, coll. Bundrick; (LACM 1999-49.3), 1 spec., female, 24 Oct. 1999, coll. Bundrick; (LACM 1999- 50.1), 1 spec., female, 21 Nov. 1999, coll. Bundrick; (LACM 1999-50.2), 1 spec., female, 21 Nov. 1999, coll. Bundrick; (LACM 1999-051.1), 1 spec., female, 7 Dec. 1999, coll. Bundrick; (LACM 2000- 1.1), 1 spec., brooding female, 19 Feb. 2000, coll. Bundrick; (LACM 2000-1.2), 1 spec., brood- ing female, 19 Feb. 2000, coll. Bundrick; (CASIZ 1238), 1 spec., 3 Jun. 1973, coll. Nakashima; (CASIZ 9550), 1 spec., Jewell Cave, Southeast Far- allon Island, intertidal, 30 Aug.-2 Sep. 1975, coll. Chaffee, Lindberg; (CASIZ 15733), 2 spec., Hop- kins Marine Station, 1921, coll. Wallace. DIAGNOSIS. Adult body size small; dd 2. 0-4. 2 mm; AL 9.6-23.8 mm (Fig. 1). Dorsal disk scales irregularly arranged, primary plates inconspicuous or lacking, boundary between dorsal and ventral disk scales not sharply demarcated (Figs. 2, 3). Ra- dial shields nearly semicircular, width of peripheral Contributions in Science, Number 486 scale capping its distal edge equals or exceeds one- half width of the shield. Ventral arm plate subpen- tagonal; distal edge longest, with medial indenta- tion forming two distolateral lobes. Three erect arm spines; dorsal and ventral spines proximodistally compressed, with bluntly rounded or flared tip; middle spine wing-shaped in dorsal view, base tri- angular in cross section with dorsoventrally com- pressed distal edge forming keel, outer portion of spine proximodistally compressed, ovoid to round- ed in cross section, with tapering to bluntly round- ed tip. Tentacle scale single, elongate, ovoid to bi- lobate; scale length on arm joints beneath disk ap- proximately one-half that of associated ventral arm plate. DESCRIPTION OF HOLOTYPE. Disk diameter 3.3 mm; AL 16.8 mm. Disk. Rounded pentagonal, lacking mid-interra- dial notches, covered by irregularly arranged, im- bricating scales; boundary between dorsal and ven- tral disk scales not sharply demarcated by closely aligned marginal scales. Primary plates inconspic- uous or lacking. Scales opaque, somewhat irregu- larly shaped, with rounded edges; largest in dorsal interradial region, smallest in ventral interradii. Genital scales inconspicuous, tilting into bursal slit, appearing similar in size to ventral interradial scales. Bursal slit extending from near posterior margin of oral shield almost to edge of disk. Hendler and Bundrick: New Brooding Brittle Star ■ 3 4 ■ Contributions in Science, Number 486 Hendler and Bundrick: New Brooding Brittle Star Radial Shield. Nearly semicircular, narrowing proximally, with broad, straight distal end; length equaling approximately one third of disk radius. Peripheral scale capping distal end of radial shield, subquadrate, thick, width equaling or exceeding one-half width of radial shield. Paired radial shields in contact distally; proximal ends separated by broad wedge-shaped scale, and frequently by nar- row wedge-shaped scale distad. Jaw. Narrow, with three, bluntly rounded oral papillae. Oral slits wide. Paired infradental papillae largest, blocklike, not markedly inflated, tapering distally, tilting upward toward teeth. Distal papillae erect, tabulate. Middle papilla smallest, elongate, with distal edge truncate, broader than base. Outer papilla elongate, with tapered, bluntly rounded dis- tal edge. Oral Shield. Rhombic, with bluntly rounded cor- ners, width equaling or exceeding length. Proximal edges somewhat convex, longer than distal edges. Madreporite larger, rounder than oral shield; distal side expanded, convex, with single pore. Adoral Shield. Long, narrow proximal lobe aligned with oral shield; short, distal lobe abutting first ventral arm plate. Paired shields touching with- in, or nearly so. Arm. Constricted basally, gradually widening over approximately one-quarter total length, taper- ing to slender distal tip; broader than high in cross section; convex dorsally, flat ventrally. Dorsal Arm Plate. Subhexagonal, twice as wide as long. Proximal edge convex; proximolateral edge meeting somewhat shorter posterolateral edge forming rounded projection; distal edge indented medially. Proximal plates slightly overlapping. Dis- tal plates three-sided, separated by lateral arm plates, with straight obtusely angled proximal edg- es meeting at sharp apex, convex distal edge. Lateral Arm Plate. Slender, with protruding ar- ticulation ridge. Dorsal side forming small, trian- gular wedge between dorsal arm plates, ventral side forming larger narrow wedge separating ventral arm plates. Successive plates joined by sheath of integument. Ventral Arm Plate. Subpentagonal, width equal- ing or exceeding length. Proximal portion relatively thickened. Proximal edges somewhat concave, meeting at sharp obtusely angled apex; lateral edges convex, excavated to accommodate tentacle scale; distal edge longest, with medial indentation demar- cating two distolateral lobes. Distal plates pentag- onal, straight sided. First ventral arm plate inclining into oral slit, nearly perpendicular to ventral sur- face of disk; portion within oral slit, thin, narrow; outer portion C-shaped, thickened, forming flat shelf between adoral shields. Arm Spines. Erect, three in number (except two on first joint beneath disk); length of spines ap- proximately equal, slightly less than width of ven- tral arm plate. At base of arm: dorsal spine proxi- modistally compressed, broader than thick, with somewhat concave distal side, outer tip bluntly rounded to flared; middle spine wing-shaped in dorsal view, base triangular in cross section, with distal edge dorsoventrally compressed, keel-shaped; outer portion of spine proximodistally compressed, ovoid to rounded in cross section, tapering to bluntly rounded tip; ventral spine resembling dorsal spine though less broad, narrower at outer tip, not distally concave. Spines increasing slightly in length from dorsal to ventral. Tentacle Scale. Single, elongate, ovoid to some- what bilobate; proximal end frequently slightly widened, inserted into angle between lateral and ventral arm plates; adradial edge aligned with ex- cavated shelf on lateral edge of ventral arm plate; distal tip bluntly rounded. Length on arm joints be- neath disk approximately one-half that of associ- ated ventral arm plate. Terminal Arm Plate. Strawberry shaped, with 0- 2 sharp, minute protrusions at terminal pore. Tube Foot. Shaft tapering, translucent; tip sphe- roidal, with two to four pairs of subterminal, ven- trolateral, glandular bumps. Whitish in alcohol. Color. Dorsally mostly whitish to pale beige; disk scales opaque, concealing dark brown stomach; some disk scales gray or brown, radial shields dark gray proximally, whitish distally; portions of some dorsal and lateral arm plates dark gray or black. Ventrally, some ossicles of oral frame pale gray, arm plates with whitish edges and traces of pale gray. Some proximal tube feet with pale yellowish pig- mentation. All but gray and black coloration quick- ly lost in ethanol, most specimens fading to white. Variation. The dd of available specimens, except embryos, ranges from 2. 0-4.2 mm, AL from 13.3— 23.8 mm and the AL/dd ratio from 5. 0-6. 9. Devi- ations from the holotype are manifested in the number of pores in the madreporite, which may be zero or one, the shape of the dorsal arm plates, which have a medial indentation in the holotype but lack a conspicuous notch in most other speci- mens, and the number of wedge-shaped scales sep- arating the radial shields. Rarely, tips of ventral arm spines are flared, and basal ventral arm plates are separated by lateral arm plates. In the smaller specimens, length and width of second ventral arm plate are equal, buccal scales ( sensu Hendler, 1978) Figure 3 Ampbiodia akosmos and Amphiodia occidentalis. A-C, adult Ampbiodia akosmos, 3.5 mm dd, holotype, LACM 1993-035.004; D-F, juvenile Ampbiodia occidentalis, 3.4 mm dd, LACM 1993-036.007; G-I, adult A. occidentalis, 8.1 mm dd, LACM 1998-089.010. For each specimen, shown from left to right are: the arm base and adjoining portion of the disk in dorsal view, the arm base and adjoining portion of the disk in ventral view, the oral frame and adjoining portions of disk and arm. Scale a = 0.5 mm (A-F); scale b = 1.0 mm (G-I) Contributions in Science, Number 486 Hendler and Bundrick: New Brooding Brittle Star ■ 5 Table 1. Features distinguishing adult Amphiodia akosmos from juvenile Amphiodia occidentals of similar size (2.5- 3.6 mm dd). Species Amphiodia akosmos A. occidentals Disk scalation Peripheral scale capping distal edge of radial shield Wedge-shaped scales between radial shields Arm spines Middle arm spine Second ventral arm plate Infradental papilla Oral shield Middle oral papilla Ventral arm plate Number of tentacle scales Tentacle scale Genital scale Primary plates inconspicuous or lack- ing, scales irregularly arranged, opaque, relatively large; scales on dorsal and ventral sides not sharply demarcated at edge of disk Width >Vi width of radial shield 1-2 conspicuous scales; inner scale broad, outer scale slender Robust Wing-shaped in dorsal view, with basal portion dorsoventrally com- pressed, forming a distal keel Width > length Inclined toward teeth Width > length Truncate, broadest at distal tip Distal edge bilobate, with medial in- dentation 1 Length >Vi length of ventral arm plate Inconspicuous Primary plates conspicuous, scales symmetrically arranged, thin, rela- tively small; scales on dorsal and ventral sides sharply demarcated at edge of disk Width l9.°o ■V* © © „ Q ©s Q o . 8 S ol _Q 00 ©0© O® I® ® ! ® %; !> 0 .5 1 1.6 2 2.5 3 3.5 4 4.5 Disk diameter (mm) Figure 4 Ampbiodia akosmos and Amphiodia occidentalis. Allometric relationships between the dd and AL (top left) and the AL/dd ratio (top right) for the full size range of the specimens examined. Scatter plots of the relationship between AL and dd (bottom left) and the AL/dd ratio (bottom right) for the specimens in the size range of A. akosmos (0.5-4. 5 mm dd) (Fig. 2). Nielsen’s (1932) statement that A. occiden- talis characteristically lacks primary plates is incor- rect. Although individuals of A. occidentalis with re- generating disks do not have primary plates, they would not be confused with A. akosmos since, as noted during this study, it was only large adult in- dividuals of A. occidentalis that had regenerating disks. Amphiodia akosmos has considerably more robust arm spines than juveniles of A. occidentalis, and its middle spine is noticeably wing-shaped (Fig. 2). In addition, juvenile A. occidentalis has zero to two tentacle scales, but A. akosmos has a single, markedly elongated tentacle scale and relatively more prominent wedge-shaped scales separating the radial shields. The possession of a single tentacle scale was pre- viously suggested to distinguish the two species (Weesner, 1954; Sutton, 1975). However, we found that the number of tentacle scales of A. occidentalis shifted from zero to one to two in individuals of increasing body size. Those with no tentacle scales Contributions in Science, Number 486 were 0.54 to 3.72 mm dd (1.75 ± 0.73 [x ± SD], N = 71), those with one tentacle scale were 2.01 to 3.72 mm dd (2.90 ± 0.41, N = 31), and those with two tentacle scales were 2. 93 to 11.97 mm dd (5.51 ± 1.73, N = 162). Thus, individuals of A. akosmos with one tentacle scale spanned the size range of A. occidentalis with zero to two tentacle scales. Amphiodia akosmos lacked tentacle scales early in development, as noted for a 0.67-mm dd juvenile, but it appears that Sutton (1975) was mis- taken in stating that it can have two tentacle scales. He likely confused A. akosmos with juvenile A. oc- cidentalis. Allometric Relationship Between Arm Length and Disk Diameter. The sizes of A. akosmos and A. occidentalis overlap (Figs. 1, 4), although indi- viduals of A. occidentalis can attain a much greater size than A. akosmos, up to 12 mm dd and 164 mm AL. Although it had been suggested that the two species are distinguishable on the basis of their size and AL/dd ratio (Weesner, 1954; Sutton, 1975), that is not invariably the case. The AL/dd Hendler and Bundrick: New Brooding Brittle Star ■ 7 Table 2. Relationship between the AL and the AL/dd ratio and dd (body size) of Amphiodia akosmos and Amphiodia occidentalis. The allometric equation is shown as a power function and in a linearized form. Species Y = aXh In Y = In a + b In X N r2 fir = 0) a cr II A. occidentalis A. occidentalis A. akosmos A. akosmos AL - 2.909(dd)1756 AL/dd = 2.909(dd)0-756 AL = 1.607(dd)2177 AL/dd = 1.607(dd)1177 In AL = In AL/dd = In AL = In AL/dd = : 1.068 + 1.756(ln dd) = 1.068 + 0.756(ln dd) = 0.475 + 2.177(ln dd) : 0.475 + 1.177(ln dd) 264 0.953 264 0.789 21 0.917 21 0.764 72.879* 31.292* 14.495* 7.842* 31.500* -10.160* 7.846* 1.180 ns Abbreviations: b, the constant of allometry; fir = 0), the calculated value of t in the test for significance of the regression, where H0: correlation coefficient = 0 vs. HA: correlation coefficient 0; fib =1), the calculated value of t in the test for significant deviations from isometry, where H0: constant of allometry = 1 (i.e. isometry) vs. HA: constant of allometry 1 (i.e., allometry); * P < 0.05; ns, not significant. ratio of A. akosmos examined ranged from 0.69 to 6.89, and the ratio for A. occidentalis ranged from 0.74 to 15.79. For A. occidentalis and A. akosmos, there was a statistically significant correlation between both AL and AL/dd ratio and body size (dd) (Table 2; Fig. 4). For both species, the coefficient of determina- tion (r2) for the nonlinear allometric regressions (Y = aXb) exceeded that for linear regressions of the data (Y = a + bX). The relationships (except AL/ dd vs. dd for A. akosmos) were allometric since the hypothesis that b = 1 (b = the allometric constant) was rejected (Table 2). For both species, a single ratio of AL/dd is insufficient to characterize either species. There has been only one comparable examina- tion of the ophiuroid arm allometry, and the results also indicated a positive allometric relationship (Lopez Velez, 1956). However, the same situation likely prevails in other long-armed ophiuroid spe- cies, casting doubt on assumptions in the literature that the ratio between AL and dd is linear and in- dependent of body size. The AL and AL/dd values for many A. occiden- talis exceeded those for A. akosmos of equivalent disk size (Fig. 4). However, the difference in the values could not be reliably used to distinguish the species because the arm lengths, and AL/dd ratios, of A. akosmos and A. occidentalis of comparable body size (dd) were overlapping. Analysis of co- variance tests of the significance of differences be- tween the regression coefficients of the two species were not warranted, because of departures from normality and heteroscedasticity, even of log-trans- formed data. In small individuals, values for AL and AL/dd were depressed compared to those for adults, be- cause the production of arm joints was not initiated until after the disk formed. The smallest A. akos- mos examined was 0.67 mm dd with AL 0.42 mm. The smallest A. occidentalis was 0.54 mm dd with AL 0.4 mm, but another that was 0.67 mm dd al- ready had 1.6-mm arms. BIOLOGY. Distribution, Habitat, and Associa- tions. Amphiodia akosmos has been found at the Great Tide Pool, at Pt. Pinos, for the past 25 years 8 ■ Contributions in Science, Number 486 and possibly longer. The population at that locality is protected by an offshore reef at low tides, but subject to considerable wave surge at high tides. The species also has been found nearby at Hopkins Marine Station, where specimens were last collect- ed in 1921; more recently at Waddell Creek, Santa Cruz County, a more southerly site; and offshore in an intertidal cove at Southeastern Farallon Island. It would not be surprising to find A. akosmos at other intertidal localities in and beyond the Mon- terey region if the California and Oregon coastlines were carefully surveyed. At Pt. Pinos, the type locality, A. akosmos oc- curred in low intertidal pools that were exposed at -0.4 ft. ( — 0.1 m) mean lower low water, and sur- rounded and protected by algae-draped, granitic boulders. Individuals were found in the shallow layer of sandy sediment beneath and around cob- bles and often occurred under the same rocks as A. occidentalis and Amphipholis squamata (Delle Chiaje, 1828). As an indication of their relative numbers, more than 135 A. occidentalis were col- lected on 23-24 July 1993 in contrast to only seven A. akosmos. Occasionally, individuals of Ophio- plocus esmarki Lyman, 1874, were also found be- neath the cobbles, and Ophiothrix spiculata Le Conte, 1851, was associated with algae at the type locality. In 1993, unidentified stalked protozoans were found on A. occidentalis in the Great Tide Pool. Some of the preserved specimens of A. akosmos collected there at the same time had similar organ- isms attached to the oral frame and the basal arm spines and tube feet. Reproduction. Amphiodia akosmos broods and may be reproductive for much of the year. Brooding individuals were collected from the Great Tide Pool in May 1975 and February 1976 (Cunningham, 1977). Additional brooding individuals were found in October 1999 and February 2000 (this report). Records of the occurrence and developmental stage of the brooded embryos reinforce the notion that individuals in the Great Tide Pool population do not spawn in synchrony. They also indicate that spawning individuals shed their ripe oocytes at one Hendler and Bundrick: New Brooding Brittle Star Figure 5 Ampbiodia akosmos, 4.2 mm dd, LACM 2000-001.002. A brooding individual with interradial sections of the disk wall dissected to reveal embryos with dorsally directed arms (arrows) and pairs of ovaries (arrowheads) within the disk. Scale = 0.5 mm time, since the embryos in all bursae of brooding females are at the same stage of development. One specimen of 3.5 mm dd collected in May 1975 was brooding nine embryos, and another specimen collected in October 1999 of 3.0 mm dd contained only one embryo with one to two arm joints. One individual collected in February 2000 was brooding 10 embryos with only terminal arm plates; another was brooding 1 1 embryos with four to six arm joints (Fig. 5). Both individuals had one to five embryos in each interradius; only one inter- radius was barren. There were larger oocytes in the ovaries of the individual with larger embryos, in- dicating that vitellogenesis occurs during brooding. A single juvenile, with five arm joints, emerged from one brooding female collected in February 2000. It was capable of locomotion using its tube feet and was negatively phototactic (Bundrick, pre- viously unpublished). However, its emergence was probably premature, since the juvenile’s disk was still pink and inflated with stored yolk. The brood- ed embryos in the same female had their arms re- flected dorsally, such that their tube feet and mouth were in contact with the bursal wall in a position that may facilitate the uptake of nutrient (Walker Contributions in Science, Number 486 and Lesser, 1989; Byrne, 1994; Hendler and Tran, 2001). The three individuals collected in October, two in November, and one in December 1999, and two more in February 2000 were dissected; all were fe- male. Thus, the species could be gonochoric, but protandry and parthenogenetic reproduction can- not yet be ruled out without further study. The fe- males had a total of 10 gonads, two within each ventral interradius; additional gonadal tubules were not observed dorsal to the arms (Fig. 5). Each ovary contained approximately one to four oocytes, and individuals appeared to have 30 or fewer pinkish- orange colored oocytes. Most of the oocytes were smaller and contained less yolk than the largest, which was 430 (xm in diameter. One A. akosmos embryo with a single arm joint was found to have a 400 |am dd. It is likely that it developed from an oocyte of approximately that diameter, since early developmental stages of brooding ophiuroids are often similar in size to the oocytes from which they arise (Hendler, previously unpublished). The low fecundity and the presence of large yolky eggs not- ed in A. akosmos are not unusual traits among brooding ophiuroids (Hendler, 1991). Hendler and Bundrick: New Brooding Brittle Star ■ 9 In contrast to A. akosmos, the larger, but mor- phologically similar, species A. occidentalis is a gonochoric broadcast spawner that releases gam- etes between late May and June in Monterey Bay (Rumrill and Pearse, 1985). Adult individuals were reported to have up to 67,965 yellow-green eggs with a maximum diameter of 90-106 |mm, and pe- lagic larvae (Rumrill and Pearse, 1985; Strathmann and Rumrill, 1987). However, an unpublished study of the species carried out at Friday Harbor, Washington indicated the eggs are orange-pink in color and 190 fxm in diameter and that develop- ment is benthic, rapid, and direct, producing crawl- ing embryos that hatch from a thick, sticky fertil- ization envelope (Emlet, personal communication). Ampbiodia occidentalis was collected from the Great Tide Pool, California, and Pt. Arago, Oregon, in June 1994. The females examined were undergoing oogenesis and had oocytes of mixed siz- es. The largest ripe oocytes were pink and approx- imately 160-192 jam in diameter, consistent with Emlet’s observations (Hendler, previously unpub- lished). In the previous literature, only one nominal spe- cies of Ampbiodia, A. affinis (Studer, 1885), was reported to brood embryos (Mortensen, 1936; Hendler, 1991). Its generic placement is unclear, but it is definitely not an Ampbiodia (Clark, 1970; Thomas, 1975). Thus, A. akosmos presently is the only Ampbiodia species known to bear live young. It would be unusual among brooding ophiuroids in having separate sexes, if it is indeed gonochoric. Among the approximately 70 known species of brooding ophiuroids only 13 species are gonochor- ic, but 40 species are hermaphroditic (Hendler, 1991; Hendler and Tran, 2001). The strong asso- ciation between brooding and hermaphroditism among the ophiuroids remains an enigma (Hendler, 1975, 1991). The brooding mode of reproduction in this and other diminutive ophiuroids may, as pre- viously suggested (Hendler, 1991), offset disadvan- tages inherent in their small size. Behavior and Morphology. Adult individuals propel themselves by simultaneously shifting the position of their arms and walking on their tube feet. Individuals quickly retract their arms when disturbed. As it is drawn toward the disk, each arm kinks into sinusoidal waves, which compress into figure eight-shaped loops. Loops at the base of the arm are largest, and those of adjacent arms inter- digitate. The five retracted arms form a tightly coiled mass on the dorsal surface of the disk, giving the animal a spherical shape. The behavior is rapid when an individual is wafted into the water column and results in its quickly sinking to the bottom like a pebble. A similar behavior is shown by A. occi- dentalis. The great morphological similarity of A. akos- mos and A. occidentalis, the direct development of their embryos, and their similar behavior and over- lapping ranges, suggest that they are closely related. Certain features of A. akosmos give it a juvenile 10 ■ Contributions in Science, Number 486 appearance: its relatively short arms, small number of disk scales, single tentacle scale, narrow arm plates, and broad radial shields. This suggests that it is paedomorphic (as defined by Gould, 1977). However, other traits of A. akosmos give it the ap- pearance of a small ophiuroid species with some adult features, and suggest that it is peramorphic. It develops large tentacle scales and conspicuous wedge-shaped scales separating the radial shields at a smaller body size than many individuals of A. occidentalis. Moreover, its relatively broad second ventral arm plate is more like those of adult than of juvenile A. occidentalis. However, its peculiarly elongated tentacle scale, robust arm spines, and rel- atively large, opaque, irregularly arranged disk scales differ from the features of both juvenile and adult A. occidentalis and may represent adult fea- tures or traits that arose de novo. It is tempting to view A. akosmos as progenet- ic — exhibiting precocious sexual maturation and retaining the juvenile characters of its ancestral spe- cies. The same mechanism has been proposed as an agent in the evolution of other species of Ophiu- roidea (e.g. Matsumoto, 1917; Hendler, 1979; Va- don, 1990). However, assessments of heterochrony require a phylogenetic framework, so that ontoge- netic trajectories between ancestral and derived species can be compared. Unfortunately, the nec- essary framework is lacking in the putative cases of ophiuroid paedomorphosis. Furthermore, as Raff (1996) has emphasized, characteristics that are pre- sumed to be evidence of heterochrony can be the end result of other mechanisms, which are poorly understood. Thus, a better understanding of onto- genetic processes and of phylogeny in Ampbiodia species are both necessary for a satisfactory appre- ciation of the evolution in the genus. ACKNOWLEDGMENTS R. Emlet, F. Nishida, R. Strathmann, J. Watanabe, Friday Harbor Laboratories, Hopkins Marine Station, University of Oregon Institute of Marine Biology, and Monterey Bay Aquarium offered assistance and laboratory accommo- dations. W. Austin, M. Behrens, R. Emlet, J. Pearse, S. Rumrill, M. Sewell, and J. Tupen provided specimens for study. R. Gustafson, C. Hand, D. Mykles, and F. Lech- leitner (nee Weesner) supplied background information; R. Emlet offered unpublished data; F. Bayer provided no- menclatorial guidance; L. Tran assisted with data analysis; and F. Nishida reviewed the manuscript. D. Pawson and C. Ahearn at the Smithsonian Institution, R. Mooi and R. Van Syoc at the California Academy of Sciences, and F. Collier at the Museum of Comparative Zoology made ma- terial in their collections available for study. J. Dearborn, D. Pawson, and the museum’s editorial committee read and commented on the manuscript. We are grateful to all for their help. LITERATURE CITED Austin, W. C. and M. G. Hadfield. 1980. 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