LARVAL DEVELOPMENT OF THE NEON GOBY, ELACATINUS OCEANOPS, IN FLORIDA! HENRY A. FEDDERN Institute of Marine Science, University of Miami ABSTRACT Spawning of Elacatinus oceanops in coastal waters of southern Florida occurs from February to April. Small juveniles become abundant in the habitat in April. The egg capsule, 2.3 mm in length, is demersal. Devel- opment of the embryo proceeds rapidly; hatching occurs about 175 hours after fertilization (at 24-27°C). Twelve steps in the development of embryo and larva are illustrated. All references in the literature to this species are included, and those pertaining to geographical range and to larval development are briefly dis- cussed. INTRODUCTION The neon goby, Elacatinus oceanops, is a small blackish fish with one broad blue stripe along each side. It inhabits marine waters of southern Florida, but its occurrence in island areas to the south and west is uncer- tain. It does not occur, apparently, in the Bahama Islands. Since its dis- covery and description in 1904, little scientific work has been done with it. The species noted in the Bahamas by Breder (1927: 83) and by Fowler (1944: 451), with a whitish-yellow stripe on the body, is not oceanops, nor is the species reported from Bonaire by Eibl-Eibesfeldt (1955). The species allied to oceanops are under study by Dr. James E. Bohlke. Biological investigations reported in the scientific literature have mainly concerned descriptions of parasite-picking activities, while those in aquar- ium journals have concerned aquarium suitability and spawning activities. These accounts of spawning activities have been mainly observational, and the only comments on larval development have been estimates of the time sequences of development. The present paper describes the morphology of eggs and young larvae of this species. Wickler (1962: 201-205) described the egg and larva of a species of neon goby, under the name Elacatinus oceanops, but the de- scriptions and figures included in his report, when compared to those pre- sented below, show differences in development time for the egg, and gross morphological differences in the size and shape of the egg capsule, embryo, and larva. Spawning behavior of the adults is also different. Unfortunately, the locality data of the adults used by Wickler could not be obtained. 1 Contribution No. 779 from the Institute of Marine Science, University of Miami. 368 Bulletin of Marine Science [17(2) ACKNOWLEDGMENTS I thank Drs. C. Richard Robins (Institute of Marine Science, University of Miami) and Walter R. Courtenay, Jr. (Boston University) for help in the preparation of the manuscript. Thanks are also given to Mr. Warren Zeiller of the Seaquarium, Rickenbacker Causeway, Miami, for donations of larvae, and enthusiastic help. This paper is part of a program of research on reef-fish biology sup- ported by the National Science Foundation (NSF-GB-1450, C. Richard Robins, principal investigator). MATERIALS AND METHODS Pairs of adults subequal in size were caught by handnet from coral heads in reef areas of the Florida Keys and near Miami, in 1962. Each pair was placed in a 20-gallon open-system marine aquarium in which temperatures ranged from 24 to 27°C. Dead tridacnid shells were provided for spawning surfaces. Food supplied to the fish consisted of small amphi- pods and frozen daphnia. Among juveniles and adults, there is no gross variation of the color pat- tern, as far as sex, spawning, or growth are concerned. A ripe female can be recognized by the large white egg mass showing through the swollen, translucent abdomen. Males are slim and smoothly tapered. The initiative in courtship was taken by the male, whose first observed action was that of a violent swimming motion while clinging with the pel- vic cup to the bottom of the aquarium. Then, the male butted the female in the head and genital region with his nose, as well as slapping her in the head with his caudal fin. Spawning took place under the shell, with the eggs, about one hundred in number, laid close together one layer deep in a circular area on the underside of the shell. The male normally guarded the nest, but did not chase the female if she came into it. If the aquarium was disturbed during the time of the male's guard duty, however, he would commonly eat the eggs. After spawning occurred, the nest was taken from the parents and placed in a plastic bucket connected with the water system. At regular intervals, samples of 3 or 4 eggs were removed from the nest, examined with a mi- croscope, and illustrated with a camera lucida. A series of 12 specimens of eggs and larvae is illustrated, to demon- strate the changes in morphology that occur during the development of individuals of this species. Figures 1-10 are of eggs and larvae spawned and raised in aquaria, from parents caught by the author. Figures 11 and 12 are of free-swimming larvae obtained from one of the Seaquarium's 500-gallon wall aquaria, where spawning had taken place. 1967] Feddern: Larval Development of Neon Goby 369 Elacatinus oceanops Jordan, 1904 Elacatinus oceanops Jordan, 1904: 542, pI. 2, fig. 3 (original description; type locality Garden Key, Tortugas, Florida; habitat on coral heads at depths of 3- 8 feet; type, Stanford Nat. Hist. Mus. 8365; cotype #2757, U. S. Fish Comm.; swimming behavior) .-Jordan & Thompson, 1905: 252 (Tortugas).- Reighard, 1908: fig. 8 (on coral head), 297, 299, 302-303, 309 (investiga- tion of immunity coloration) .-Jordan, Evermann & Clark, 1930: 442 (Gar- den Key, Tortugas, Fla.) .-Longley & Hildebrand, 1941: 226 (parasite- picking behavior; coloration) .-Boyd, 1956: 391-396 (spawning behavior).- Simkatis, 1958: 104 (treatment with copper sulfate), 165-167, fig. 33 (in aquaria).-Bailey et al., 1960: 35 (listed).-Randall, 1962: 43,46 (figure; parasite-picking behavior) .-Axelrod & Vorderwingler, 1963: 199 (photo), 264-265 (common names; range; coloration; maximum size).-Phillips, 1964: 49-51 (parasite-picking behavior). Gobiosoma oceanops, Ginsburg, 1933: 2,19,21-22 (key; Garden Key, Florida; description).-Briggs, 1958: 288 (range).-Duarte-Bello, 1959: 123 (range). Lactinius oceanhops, Fisher, 1955: 36-37, 70 (name misspelled; general and spawning behavior in aquaria). Lactinius oceanops, Straughan, 1959: 140-144, figs. 62 & 63 (name misspelled; spawning in aquaria; spawning behavior; general description of larvae and larval growth).-Straughan, 1964: 165-169, figs. 21, 56, 72, 73, & 75 (spawning in aquaria). Elecatinus oceanops, Herald, 1961: 235, pI. 100 (name misspelled; parasite- picking behavior; spawning behavior) .-Limbaugh, 1961: 43 (parasite-pick- ing behavior). ? Elacatinus oceanops, Wickler, 1962: 201-205 (general and spawning behav- ior; description and figures of egg and larva). not Elacatinus oceanops, Breder, 1927: 83 (West Indies).-Fowler, 1944: 451 (Bahamas) .-Eibl-Eibesfeldt, 1955: 207-209, figs. 5-7 (description; parasite- picking activity; at Bonaire, Dutch West Indies). not Gobiosoma oceanops, Erdman, 1956: 335 (Jamaica; Haiti; Puerto Rico). DESCRIPTIONS Nearly all eggs in the nest are encased in a tough, flexible, transparent, conical, fluid-filled capsule 2.3 mm long. The basal, small end of the cap- sule possesses a mass of adhesive threads by which the capsule is anchored to the substrate. The free, large end of the capsule is rounded, with 5 or 6 conical projections surrounding the end in a marginal ring. Infertile eggs had capsules only slightly oblong, and measuring I mm long. A few embryos lacked capsules, the adhesive threads attaching the em- bryos directly to the substrate. These embryos lagged in development and died after about 50 hours. None of the eggs contained oil globules, and if detached from the sub- strate, they sank. Specimen 1 (Figure la, less than 3 hours old).-The egg has already passed through many cleavage stages, for a cap of cells can be seen on the lower portion of the yolk, the latter consisting of transparent globules of fairly uniform size. 370 Bulletin of Marine Science [17(2) 1967] Feddern: Larval Development of Neon Goby 371 Specimen 2 (Figure 1b, about 16 hours).-A hemisphere of cells about one-third the size of the yolk hemisphere has formed. The mass of adhe- sive threads has been omitted from this and the following illustrations for simplicity. Specimen 3 (Figure 1c, about 28 hours).-The primitive streak has formed and embryonic precursors of the head and body are developing. A dorsal view shows as yet no definite structures. Specimen 4 (Figure 1d, about 50 hours).-Many myomeres are forming along the mid-body region. The head, eyes, tail, notochord, and nerve cord are noticeable. The yolk mass is still very large. Specimen 5 (Figure Ie, about 74 hours).-The posterior two-thirds of the body is now divided into myomeres (numbers shown are approximate). The brain has begun to develop. Eyes are in an advanced stage of devel- opment, with the pupils present. Specimen 6 (Figure 1£, about 100 hours) .-A vertical fin-fold has devel- oped around the entire posterior portion of the body. Hindgut, eye, brain, and nerve cord are in a more advanced stage of development. The heart, located in a small sac in front of the yolk sac and postero-ventral to the head, is beating. The blood is colorless. Specimen 7 (Figure 19, about 125 hours).-The heart has differentiated into chambers, and circulates pigmented blood through the body; the major pattern of flow is indicated by arrows on the illustration. The main return of the blood to the heart is around the ventral side of the yolk sac. (Myo- meres are omitted to show blood flow.) The chorion of the eye is black. Ossification of the vertebrae is distinct. Specimen 8 (Figure 1h, about 150 hours).-Pectoral fins are developing, and the vertical fin-fold has partially separated into dorsal, caudal, and anal fins, although no fin rays are apparent.