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Twelve olive ridleys were sampled for epibionts while nesting at Playa Ceuta, Elota, Sinaloa, Mexico from July-December 2006. The mean curved carapace length for the turtles sampled was 65.3 cm (±1.8 SD range: 60-69 cm). Conspicuous epibiota were removed and fixed in 10% formalin. For storage, epibionts were removed from formalin, rinsed and placed in 70% isopropyl alcohol. Samples were sorted and identified to the lowest taxon possible. Because the focus of this study was to document the diversity of epibionts present on olive ridleys in Sinaloa, epibiont species that had already been collected were not sampled in subsequent observations. Thus, we do not provide data on the frequency of occurrence of the epibionts described herein. Additionally, due to the possibility of infection, burrowing barnacles from the skin of olive ridleys were not removed. However, we are currently undertaking studies that examine these species from dead olive ridleys that strand at Playa Ceuta and these results will be presented in a later report.

Figure 1. Epibionts collected from Lepidochelys olivacea nesting in Sinaloa: A. Chelonibia testudinaria with specimens of Conchoderma virgatum attached, B. Ozobranchus branchiatus, C. Conchoderma virgatum, D. Lepas anserifera, E. Planes cyaneus heterosexual pair, female (left) and male (right).

We identified 5 epibiotic species from olive ridleys nesting at Playa Ceuta (Figure 1). Coronuloid turtle barnacles, Chelonibia testudinaria (Figure 1A), were largely confined to the anterior portion of the carapace, particularly along the anterior margin and occasionally on the underside of the posterior margin of the carapace near the tail. Leeches, Ozobranchus branchiatus (Figure 1B), were commonly attached to the soft skin of the shoulder region, adjacent to the flippers and the soft skin areas on the underside of host turtles. Lepadomorph barnacles, Conchoderma virgatum (Figure 1C) and Lepas anserifera (Figure 1D), were commonly found attached to the neck and shoulder regions of host turtles, often in high densities and appearing from afar as leeches. Conchoderma virgatum was also common on the flippers and plastron and was occasionally found attached to specimens of C. testudinaria (Figure 1A). Lepas anserifera was also found attached to the posterior third of the carapace (Figure 1D) and ours is the first report of this species from olive ridleys. Grapsid crabs, Planes cyaneus (Figure 1E), were collected from the underside of turtles in the tail region, always appearing as heterosexual pairs.

Our results coincide with other epibiont studies conducted on olive ridley nesting beaches along the Pacific coast of Mexico: La Gloria in Jalisco (Hernández-Vázquez & Valadez-González 1998); Playa Calabazas in Michoacán, and Playas Escobilla and Morro Ayuta in Oaxaca (Gámez Vivaldo et al. 2006). That is, ridleys nesting in this area host relatively few epibiont species, and the non-obligate species present are largely pelagic/oceanic in nature (i.e. C. virgatum, Lepas sp. and P. cyaneus). Conversely, studies conducted on the epibionts of nesting olive ridleys in Orissa, India report largely benthic/neritic non-obligate species from ridleys in this area (Frazier et al. 1985; Mohanty-Hejmadi et al. 1989). Apparently there are internesting behavior differences between these two widely separated olive ridley populations despite the fact that both populations are conspecific. Thus, it appears that olive ridleys nesting along the west coast of Mexico spend a great deal of time at or near the water surface during the internesting period (possibly in oceanic habitats), whereas ridleys nesting in India spend a substantial amount of time in coastal habitats during internesting periods (possibly in benthic or estuarine habitats). Telemetry studies on Mexican and Indian olive ridleys would help to reinforce these differences in internesting behavior.

While examining the literature on the epibionts of olive ridleys we encountered several incorrectly identified epibiont species illustrated by Gámez Vivaldo et al. (2006). The aforementioned study provides four photographic figures, three of which are incorrectly described (therein Figures 1, 3 & 4). Figure 1 is labeled as ‘Crustacea: Cirripedia: Conchoderma virgatum’, but is actually a photograph of several Lepas sp. barnacles. Figure 3 is labeled ‘Crustacea: Cirripedia: Chelonibia testudinaria’, but actually depicts three different obligate commensal barnacle species: C. testudinaria (top left), Stomatolepas sp. (top right) and Platylepas hexastylos (bottom: dorsal view/left, ventral view/right). Figure 4 is labeled ‘Crustacea: Amfipoda [sic]: Caprella sp.’, but actually depicts Gammaroid amphipods, likely the obligate commensal of marine turtles: Podocerus chelonophilus. Another study from México, Hernández-Vázquez & Valadez-González (1998), reports Gammaroid amphipods from nesting olive ridleys but does not identify the species in question. Future studies on the Gammaroid amphipods of olive ridleys should seek to identify the species in question as a record of P. chelonophilus would be the first for any marine chelonian other than loggerheads (Caretta caretta).

Acknowledgments: We thank all members of the Escuela de Biologia of the Universidad Autonoma de Sinaloa that work in the turtle camp at Ceuta, Victor Manuel Salomon Soto, Ingmar Sosa Cornejo, Francisco Enciso Saracho of the Facultad de Ciencias del Mar, UAS for supporting our research and special thanks to Marcos Bucio Pacheco for helping us with this study. Matthew Godfrey and two anonymous reviewers provided comments that greatly improved this ms.

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