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Marine Turtle Newsletter 45:11-13, © 1989

Commensals on the Olive Ridley Sea Turtle

P. Mohanty-Hejmadi, M. Behera and S.K. Dutta
Department of Zoology, Utkal University, Vani Vihar, Bhubaneswar 751004, Orissa, India

Gahirmatha beach (20°42'N, 87°5'E), in the Bhitarkanika Wildlife Sanctuary, Orissa, India, is the largest rookery in the world for olive ridley turtles, Lepidochelys olivacea (Anon., 1986). During field studies on the mass nesting in March 1987 we collected commensals colonizing the carapace and body of turtles coming ashore to nest. Commensals were absent from anterior carapace regions, perhaps because these areas are continuously abraded by the foreflippers during swimming.

Sedentary commensals were scraped from the carapace and neck regions of gravid turtles (n=50) and preserved in 70% alcohol. The preserved specimens were examined under a binocular microscope. Identification was done following Hyman (1940) and Smith and Weldon (1909). Seven invertebrates were identified in three phyla: Cnidaria (n=5), Porifera (n=1) and Anthropoda (n=1). The most common commensal, Bougainvillia (Fig. 1), was found attached to the whole surface of the carapace (with the exception of areas abraded by the foreflippers); these colonies were light brown in colour. The sea anemones Metridium (Fig. 2) and Adamsia (Fig. 3) were also common on the carapace. Most individuals were observed in a contracted position. The colour of the animals was white, pink or yellowish-white. Adamsia was distinguished from Metridium by the oral tentacles.

Less common was a cnidarian in the order Stolonifera (Fig. 4) which was collected from the carapace of only a single turtle. The colony was white and consisted of 15 polyps. A colony of a small cnidarian in the sub-class Zoantharia (Hexacorallia) (Fig. 5) was likewise collected from only one turtle. The colour of the colony was white; some were attached to Balanus barnacles which had colonized the turtle's carapace.

In the phylum Porifera, the "crumb of bread sponge" (Fig. 6) was collected from the margin of one turtle's carapace. The colour of the sponge was yellowish-white. Profuse bleeding from the site of attachment was observed upon removal of the sponge. Perhaps there was some vascular connection between sponge and carapace, or perhaps the increased vascularization beneath the sponge resulted from a localized immune response to chemicals diffusing from the sponge tissue. Finally, the cirriped Balanus was common to the carapace and neck regions of the turtles.

We would like to thank the Department of Environment, Government of India (No.14011/5/84 EG-7) for providing financial support for this study. We would also like to thank Shri R.N. Mohanty (Additional Chief Conservator of Forest and Wildlife Warden) and Shri S.K. Mishra (D.F.O. Chandabali) for their help and cooperation during this study.

Anonymous. 1986. Olive ridleys recovering. Orynx, April 1986:124. (original source: Commonwealth 1986, 28:3).

Hyman, L. H. 1940. The Invertebrates: Protozoa through Ctenophora. McGraw-Hill Book Company, New York.

Smith, G. and W.F.R. Weldon. 1909. Crustacea. In: The Cambridge Natural History, Vol IV (S.F. Harmer and A.E. Shipley, eds.). Macmillan & Co., Ltd., London. p.1-252.