Copeia, 2002(4), pp. 1134–1136
Observations on Microhabitat Utilization by Three Widely Distributed Neotropical Gobies of the Genus Elacatinus MICHAEL S. TAYLOR
AND JAMES
L. VAN TASSELL
The family Gobiidae is the largest family of marine fishes, yet microhabitats of most gobies are poorly known. We sampled different coral reef macrohabitats from Jamaica and Grand Cayman to identify microhabitats occupied by three species of the genus Elacatinus. Elacatinus gemmatus and Elacatinus pallens were found in association with burrows created by the chiton, Choneplax lata. Between island differences in microhabitats occupied by Elacatinus dilepis could represent a shift because of reef degradation in Jamaica.
T
HE family Gobiidae is the largest family of marine fishes (Nelson, 1994), yet gobies are often poorly represented in regional faunal texts (Bellwood and Hughes, 2001). In the tropical northwestern Atlantic Ocean, gobies are the most species-rich family of fishes found on coral reefs (Robertson, 1998), but how these gobies use microhabitats within the reef is largely uninvestigated, which contributes to poor knowledge of faunal assemblages (Greenfield and Johnson, 1999). Knowledge of how microhabitats are used by gobies, especially by closely related species, can provide critical insight into understanding how high goby diversity is maintained on coral reefs and may also reveal clues to processes leading to the origin of those species. Typically, only the habitats of colorful or otherwise exposed species are well known. Cryptic coloration and an often secretive nature make discovery of habitat use by many goby species a difficult prospect. Cryptic species are often discovered and collected by application of ichthyotoxins to broad areas (e.g., Greenfield and Johnson, 1999), but the specific microhabitat occupied by such species cannot be accurately determined with this method. The goby genus Elacatinus, with 20 described species in the tropical western Atlantic Ocean (Bo¨hlke and Robins, 1968; Sazima et al., 1997), is the largest genus of fishes found on the coral reefs of this region. We follow Hoese (1971) and Eschmeyer (1998) by recognizing the genus Elacatinus with two subgenera, Elacatinus and Tigrigobius, although some authorities place both subgenera in the genus Gobiosoma (e.g., Robins et al., 1991). The brightly colored neon gobies of the subgenus Elacatinus occupy well-defined microhabitats, including tube sponges and massive coral heads (Colin, 1975; Sazima et al., 1997). However, the microhabitats remain obscure for at least three of the seven cryptic Tigrigobius species found in the Atlantic Ocean. We surveyed a variety of coral reef and reef-as-
sociated habitats at two Caribbean islands through careful application of small quantities of very dilute anaesthetic to define the microhabitat of Elacatinus gemmatus and Elacatinus pallens, two widely distributed but rarely observed species found throughout the Bahamas and Caribbean Sea. A third species, Elacatinus dilepis, occupied microhabitats that differed between healthy and degraded reefs, which could result from loss of preferred microhabitat on degraded reefs. MATERIALS
AND
METHODS
Three SCUBA divers randomly surveyed a diversity of macrohabitats at the Hofstra University Marine Laboratory, St. Ann’s Bay, Jamaica, and along the north and south shores of Grand Cayman during June 2001. Sampled macrohabitats included deep sloping and vertical forereef (15 to 40 m depth), spur and groove formations (6–20 m), fringing reef and interior lagoons (1–6 m), and flat, limestone substrate with varying amounts of relief and scattered scleractinian coral heads and gorgonians (2–5 m). Each macrohabitat type was surveyed in roughly equal amounts for a total of 75 divehours. Within each macrohabitat type, we administered extremely dilute solutions (, 2%) of clove oil or quinaldine sulfate from squirt bottles into or around different microhabitats, such as small crevices, algal mats, sand burrows, and the bases of corals and sponges. This method sufficiently agitated gobies (and other fishes and invertebrates) to drive them from seclusion, but the solution was too dilute for the organisms to succumb to the anaesthetic. Three species of the genus Elacatinus, subgenus Tigrigobius were observed. Representative goby individuals were captured with a 25 3 18 3 22 cm mesh dipnet, returned to the lab, and photographed to confirm identification. A voucher specimen for each species has been deposited at the Uni-
q 2002 by the American Society of Ichthyologists and Herpetologists
TAYLOR AND VAN TASSELL—TIGRIGOBIUS MICROHABITAT USE versity of Florida Museum of Natural History (E. gemmatus, UF 119518; E. pallens, UF 119519, and E. dilepis, UF 119520). Institutional abbreviation follows Leviton et al. (1985). RESULTS Elacatinus gemmatus.—This species has been collected previously throughout the Bahamas and Caribbean Sea from near shore to depths of 10 m (Bo¨hlke and Chaplin, 1968). We located E. gemmatus only at Grand Cayman; this species has not been reported previously from Jamaica. Collections from the Gulf of Honduras have shown E. gemmatus to most often occupy patch reef and rocky macrohabitats but microhabitats were not identified (Greenfield and Johnson, 1999). We observed both juvenile and adult E. gemmatus occupying burrows created by the chiton Choneplax lata. The chiton drills clusters of discrete holes approximately 1 cm diameter while feeding on the coralline red algae, Porolithon pachydermum. These burrows form a complex, interconnected network 6–10 cm beneath the limestone surface (Littler et al., 1995). Individuals of E. gemmatus could be observed peering out of one hole but would emerge from a different hole after application of anaesthetic to the first hole. One or two individuals were observed per cluster of chiton burrows. No attempt was made to sex individuals, but two individuals collected together could potentially be a reproductive pair. Robins (1958) noted that, when two individuals of the closely related E. macrodon were collected together, they typically were male and female. We did not observe E. gemmatus in any other microhabitat. In most observations, E. gemmatus was observed in chiton burrows that were free of silt and other debris. In one instance, a pair of E. gemmatus were captured from a cluster of apparently older C. lata holes on a small patch reef inside a heavily silted, shallow lagoon on the south shore of Grand Cayman. Thus, we conclude that E. gemmatus occupies C. lata holes in a variety of habitat conditions. Other organisms inhabiting the chiton burrows included sea anemones (Lebrunia sp.), alpheid snapping shrimp, ophiuroid brittle stars, and other teleost fishes, primarily small blenniids and gobiesociids. In addition to providing habitat for a variety of organisms, the association of C. lata and P. pachydermum is a major component of Caribbean reef building systems (Littler et al., 1995). Elacatinus pallens.—Bohlke and Robins (1960, 1968) suggested that in the Bahamas E. pallens inhabited small, algae-covered limestone can-
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yons from near shore to 10 m depth; however, Greenfield and Johnson (1999) subsequently captured E. pallens from shallow forereef, patch reef, and tidepools. Attempts by one of us (MST) to collect both E. pallens and E. gemmatus from similar habitat at several locations in the Bahamas and Puerto Rico during 2000 and 2001 were unsuccessful. On Grand Cayman, we found E. pallens most frequently beneath small (15–30 cm diameter) heads of Montastrea and Siderastrea spaced irregularly across a flat limestone plain. Individuals were hidden in recesses at the bases of the coral heads and were never observed prior to administration of anaesthetic. To escape, they would typically dart away from the coral head to a nearby structure or recess. On one occasion, however, three individuals emerged from beneath a 30 cm Montastrea and darted into cavities in the upper surface of the coral head. Elacatinus pallens was also observed in C. lata burrows although with somewhat less frequency than from coral heads. Both E. gemmatus and E. pallens were often observed inhabiting the same chiton burrow. In Jamaica, we observed four adult E. pallens on a horizontal formation along the vertical side of a spur and groove formation. This sighting represents the first reported occurrence of E. pallens from Jamaica. These individuals were occupying small crevices in the limestone, which was barren of scleractinian corals or C. lata burrows. Thus, E. pallens appears to dwell among a broader array of limestone-based microhabitats than E. gemmatus. Subsequent to these observations, one of us (MST) captured two individuals of E. pallens at Grand Turk from separate C. lata burrows after approximately ten minutes of sampling effort, suggesting that E. pallens uses C. lata burrows throughout the Caribbean and Bahaman islands. This collection represents the first documentation of E. pallens from the Turks and Caicos. Elacatinus dilepis.—The microhabitat occupied by E. dilepis has been previously noted (Bo¨hlke and Chaplin, 1968; Humann, 1994; Greenfield and Johnson, 1999). This species generally perches singly or in pairs on small coral heads and sponges on small patch reefs. In Grand Cayman, we most often observed one or two juvenile to adult E. dilepis on Siderastrea siderea and other scleractinian corals at 7–10 m depth, but also observed a single adult at the base of a large sponge, Verongula gigantea, at approximately 16-m depth. Our observations around Grand Cayman revealed that E. dilepis was always observed in association with coral or sponge and never with exposed limestone. In Jamaica, how-
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ever, we only observed E. dilepis on exposed limestone encrusted with coralline red algae on the vertical sides of spur and groove reef formations. Several clusters of 4–6 individuals each were observed between 3 and 5 m depth. The apparent shift in microhabitats occupied by E. dilepis between Grand Cayman and Jamaica could be the result of loss of preferred microhabitat in Jamaica. Live coral habitat in Jamaica is severely degraded because of hurricanes, disease, and anthropogenic factors such as overfishing (Hughes, 1994). Alternatively, E. dilepis may use a broader range of microhabitats than previously realized. Greenfield and Johnson (1999) collected E. dilepis in the Gulf of Honduras from shallow rocky macrohabitats that have little or no coral (Greenfield and Johnson, 1990). Their use of ichthyoxins, however, precluded identification of the specific microhabitat used by E. dilepis. They collected E. dilepis more frequently in deeper spur and groove formations, where they visually observed E. dilepis on live corals. Thus, E. dilepis may be found on both live corals and rocky substrate, but the habitat degradation observed in Jamaica would still cause a shift away from microhabitats created by living corals. ACKNOWLEDGMENTS We thank S. Taylor for assistance in the field. T. Austin and M. Day assisted with the scientific collecting permits for Grand Cayman and Grand Turk, respectively. G. Kaplan, S. Macia and M. Robinson facilitated diving operations on Jamaica, and E. Haley and Sunset Divers facilitated diving operations on Grand Cayman. R. Robins provided catalog numbers for the voucher specimens. M. Hellberg and T. McGovern provided helpful comments on the manuscript. LITERATURE CITED BELLWOOD, D. R., AND T. P. HUGHES. 2001. Regionalscale assembly rules and biodiversity of coral reefs. Science 292:1532–1535. BO¨HLKE, J. E., AND C. G. C. CHAPLIN. 1968. Fishes of the Bahamas and adjacent tropical waters. Livingston Publishing Co., Wynnewood, PA. ———, AND C. R. ROBINS. 1960. Western Atlantic gobioid fishes of the genus Lythrypnus, with notes on Quisquilius hipoliti and Garmannia pallens. Proc. Acad. Nat. Sci. Phila. 112:73–101. ———, AND ———. 1968. Western Atlantic sevenspined gobies, with descriptions of ten new species
and a new genus, and comments on Pacific relatives. Ibid. 120:45–174. COLIN, P. L. 1975. Neon gobies. T.F.H. Publications, Inc., Neptune City, NJ. ESCHMEYER, W. N. 1998. Catalog of fishes. Vol. 3. California Academy of Sciences, San Francisco. GREENFIELD, D. W., AND R. K. JOHNSON. 1990. Community structure of western Caribbean blennioid fishes. Copeia 1990:433–448. ——— AND ———. 1999. Assemblage structure and habitat associations of western Caribbean gobies (Teleostei: Gobiidae). Ibid. 1999:251–266. HOESE, D. F. 1971. A revision of the Eastern Pacific species of the gobiid fish genus Gobiosoma, with a discussion of relationships of the genus. Unpubl. Ph.D. diss., Univ. of California, San Diego. HUGHES, T. P. 1994. Catastrophes, phase shifts, and large-scale degradation of a Caribbean coral reef. Science 265:1547–1551. HUMANN, P. 1994. Reef fish identification: Florida Caribbean Bahamas. 2d ed. New World Publications, Inc., Jacksonville, FL. LEVITON, A. E., R. H. GIBBS JR., E. HEAL, AND C. E. DAWSON. 1985. Standards in herpetology and ichthyology. Part I. Standard symbolic codes for institutional resource collections in herpetology and ichthyology. Copeia 1985:802–832. LITTLER, M. M., D. S. LITTLER, AND P. R. TAYLOR. 1995. Selective herbivore increases biomass of its prey: a chiton-coralline reef-building association. Ecology 76:1666–1681. NELSON, J. S. 1994. Fishes of the world. 3d ed. John Wiley and Sons, Inc., New York. ROBERTSON, D. R. 1998. Do coral-reef fish faunas have a distinctive taxonomic structure? Coral Reefs 17: 179–186. ROBINS, C. R. 1958. Garmannia zebrella, a new gobiid fish from Trinidad, with notes on the species of the subgenus Tigrigobius Fowler. J. Wash. Acad. Sci. 48: 192–198. ———, R. M. BAILEY, C. E. BOND, J. R. BROOKER, E. A. LACHNER, R. N. LEA, AND W. B. SCOTT. 1991. Common and scientific names of fishes from the United States and Canada. 5th ed. American Fisheries Society, Spec. Publ. 20, Bethesda, MD. SAZIMA, I., R. L. MOURA, AND R. S. ROSA. 1997. Elacatinus figaro sp. n. (Perciformes: Gobiidae), a new cleaner goby from the coast of Brazil. Aqua 2:33– 38.
(MST) DEPARTMENT OF BIOLOGICAL SCIENCES, 107 LIFE SCIENCES BUILDING, LOUISIANA STATE UNIVERSITY, BATON ROUGE, LOUISIANA 70803; AND ( JLV) DEPARTMENT OF BIOLOGY, HOFSTRA UNIVERSITY, HEMPSTEAD, NEW YORK 11549. Email: (MST)
[email protected]. Send reprint requests to MST. Submitted: 31 Dec. 2001. Accepted: 17 May 2002. Section editor: S. A. Schafer.
