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Despite over three decades of flipper tagging in some areas, it is surprising that there is little information available on the epibionts of nesting hawksbill turtles in the Caribbean. Carr et al. (1966) note the occurrence of heavily fouled nesters at Tortuguero, Costa Rica and point out large white barnacles (apparently Chelonibia sp.) on the carapace and plastron. Much of the remaining literature available on the epibionts of hawksbill turtles in the Caribbean concerns foraging turtles and immature specimens (Scharer 2001; Witzell 1983). There are no published studies that have monitored the epibiont community composition of a population of hawksbill turtles continuously throughout the course of a nesting season.

Inspired by the hawksbill turtle's propensity for epibiont growth, we initiated a study of the epibionts associated with nesting hawksbill turtles from Pasture Bay Beach, Jumby Bay, Long Island, Antigua, in the West Indies from June - November 2001. We sampled 28 individual hawksbill turtles (curved carapace length (CCL), 79.0 - 96.6 cm average = 89.2 cm) following methods outlined in Frick et al. (1998). A number of epibiont types were encountered (Table 1), usually attached to or living amongst sessile epibiota located on the posterior 1/3 of the carapace region. Several epibiont forms were also found living amongst epibiota accumulated beneath overlapping vertebral scutes, particularly the third and fourth vertebral scutes from the nuchal region.

Table 1. Epibionts from nesting hawksbill turtles (Eretmochelys imbricata) from Jumby Bay, Antigua, West Indies (n = 28 turtles).1First report as a hawksbill epibiont, 2First report as a sea turtle epibiont.

The occurrence of some epibiont species identified during this study are noteworthy because they represent the first observations of these particular species as hawksbill epibionts and, in some cases, first reports as sea turtle epibionts (see Table 1). With the exception of obligate commensals like Chelonibia barnacles and Podocerus chelonophilus amphipods, all of the epibionts collected from Jumby Bay nesters are also commonly found as free-living forms, usually associated with live bottom habitats throughout the greater Caribbean. Thus, the occurrence or density of any of the aforementioned epibionts is most likely an artifact of the seasonal or even cyclical recruitment of these forms into the marine habitats utilized by female hawksbills during internesting periods. In the present case, coastal live bottom habitats appear to be the internesting habitats used by hawksbills observed nesting in Antigua. A study by Starbird et al. (1999) reported similar internesting habitat use by nesting hawksbills from Buck Island, St. Croix, U.S. Virgin Islands. Nesting loggerheads in the southeastern U.S. commonly host epibiont taxa analogous in composition, density and abundance to the fouling communities found on submerged structures adjacent to internesting habitats and Puerto Rican hawksbill turtles at coral reef and cliff wall foraging habitats commonly host epibionts similar to the fouling communities associated with their surrounding environment (Caretta Research Project unpublished data; Scharer 2001).

Given the wide-ranging migration events documented for adult hawksbill turtles in the Caribbean, sometimes 1900+ km, and the hawksbill turtle's affinity for coastal live bottom and reef habitats, it is not surprising that the epibionts documented in this study are similar to epibiotic taxa found on hawksbill turtles throughout the Caribbean (Meylan 1999; Scharer 2001; Witzell 1983). It is possible that "reef-hopping macrofauna", like hawksbill turtles, may aid in the introduction and emigration of certain plants and animals from one reef system to another, a point worthy of consideration to any student of biodiversity.

Although it was previously mentioned that we were not surprised to find the aforementioned epibiota from Antigua nesters given the commonality of many of these species within coral reef and other live bottom habitats throughout the greater Caribbean, the occurrence of alpheid shrimp (Synalpheus fritzmuelleri) as epibionts of hawksbill turtles is, however, possibly a unique association amongst sea turtles. Alpheid shrimp are easily recognized by their single, large, modified claw or chela that is used to make distinct snapping or popping sounds. Laboratory studies indicate that the concussion wave generated by the snapping shrimp's chela, which has been observed to shatter the glass of an aquarium, serves to stun small animals (Williams 1984). A remarkable adaptation evoked for territorial disputes, protection and prey acquisition.

Known colloquially as the speckled snapping shrimp, S. fritzmuelleri is a relatively small shrimp (up to ~ 2 cm in length) that can be found in temperate to tropical waters from Beaufort, North Carolina, USA to Santa Catarina, Brazil; Gulf of Mexico; Bermuda; St. Helena Island, South Atlantic and Baja California (Chace 1966). In temperate and subtropical climes, S. fritzmuelleri breeds during the warmer months of year and year-round in tropical regions. Members of the genus Synalpheus are commonly known as "sponge shrimps", well-noted denizens of the external and internal surfaces of large sponges associated with nearshore, reef habitats; S. fritzmuelleri is no exception (Chace 1972). However, S. fritzmuelleri is also known to inhabit a variety of gaps and sinuses associated with other reef inhabitants. In southeastern Florida, USA S. fritzmuelleri is commonly found on sabellariid worm (Phragmatopoma lapidosa) reefs (Gore & Wilson 1978; Gore et al. 1976; 1978). Aside from S. fritzmuelleri's breeding periodicity and its affinity for reef habitats and reef associated sessile organisms, very little is known of the speckled snapping shrimp's life history (Williams 1984). Thus, it is difficult to speculate the nature of the relationship that exists between S. fritzmuelleri and the hawksbill turtle.

We found S. fritzmuelleri present amongst samples that were collected from the overlapping scutes of three Jumby Bay nesters (n= 3 shrimp: 1 adult male and two ovigerous females). Additionally, we found a single alpheid (an ovigerous female) living amongst epibiota within a gap formed by a carapace injury or deformation on the center of the third, right-hand costal scute of a fourth turtle. Only one other study reports the occurrence of alpheid shrimps as epibionts of sea turtles (Scharer 2001). Scharer (2001) found alpheids (identity not specified) to occur under the overlapping scutes of 3.8 % of the immature hawksbill turtles she surveyed from Puerto Rican coral reef foraging grounds near Mona Island. She also noted that epibionts situated beneath overlapping scutes were most common on immature hawksbills as the scutes of adults are typically more juxtaposed rather than imbricated - although, relatively young nesters will occasionally bear a few overlapping scutes and harbor epibionts within the associated crevices (Witzell 1983; present study). Nonetheless, it is the occurrence of S. fritzmuelleri from a carapace injury or deformation (as mentioned above) that provides reason for highlighting the association between alpheid shrimp and hawksbill turtles.

Literally hundreds of loggerhead turtles - that are known to occupy reef habitats within the range stated for S. fritzmuelleri- have been surveyed for epibiota and not once have alpheid shrimp been observed (Dodd 1988; Frick et al. 1998, 2000). A logical assumption on the matter might contend that the overlapping scutes of the hawksbill turtle, which are absent in other species of marine turtles, could influence particular epibiont associations to occur, including the occurrence of S. fritzmuelleri. Yet, we found an alpheid also inhabiting a carapace abnormality on a hawksbill turtle. In the southeastern US, another haunt of the speckled snapping shrimp, we see many loggerhead turtles (immature and adult turtles alike) with carapace injuries and deformations similar to the one observed housing S. fritzmuelleri. Such abnormalities usually appear to be as a result of interactions with boat propellers and/or caused by barnacle colonization. Nonetheless, loggerhead turtles from the southeastern US, which have been the subjects of more intensive surveys, have failed to yield any alpheid shrimp - despite the residency of some loggerheads in reef habitats and the presence of shell abnormalities that form crevices analogous to those on hawksbills.

It is possible that behavioral differences in S. fritzmuelleri from widely separated localities may exist and epibiosis on turtles does not factor into the life history plan of some populations. Or, behavioral differences between hawksbill and loggerhead turtles may account for the occurrence of alpheid shrimp on the former and not the latter. It is also possible that the spongivorous feeding habit of hawksbills (Bjorndal 1997; Meylan 1988) prompts the occurrence of alpheid colonization. Perhaps alpheids emigrate onto hawksbills as the turtles consume sponges hosting snapping shrimp; after all it would be better to live atop the predator rather than the prey. Until more investigations of this topic are initiated and other turtle species with carapace abnormalities suitable for alpheid colonization are surveyed, the relationship between alpheid shrimp and hawksbills will remain potentially unique among sea turtles.

Acknowledgments: We thank the Jumby Bay Club and Resort, John and Sarah Fuller, Jim and Thelma Richardson, Rebecca Bell, Karen Eckert and others from WIDECAST, the Turner Foundation, the National Fish and Wildlife Foundation, the PADI Foundation, Arnold Ross, John Robinette, Deb Keineth, Peter Range, Charles and Mary Lee Warnock, Randy Isbister, Robert A. Moulis, Mark Dodd, Adam MacKinnon, and Barb Zoodsma. The manuscript was improved by the comments of two referees.

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