MTN 47:10-11 Are Marine Turtles Free from Parasitic Copepods?

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Are Marine Turtles Free from Parasitic Copepods?

Jack Frazier
Programa Regional de Vida Silvestre, Apartado 1350, Heredia, Costa Rica

Parasitic copepods are found on a wide variety of marine invertebrates and vertebrates, ranging from cartilaginous and teleost fishes (Yamaguti, 1963; Cressey and Lachner, 1970; Hogans, 1986) to whales (Dailey and Brownell, 1972). There are over 70 genera of these parasites, of which Penella is one of the best known (Balaenophilus listed by Dailey and Brownell [1972:561] is not a copepod, but a barnacle). These parasitic crustaceans show varying degrees of host specificity.

Despite the fact that most copepods are free-living and so small as to be barely visible to the naked eye, these obligate parasites may grow to over 1 m in length. Many burrow into the skin of the vertebrate host, sometimes reaching internal organs, then become affixed and eventually metamorphose to form little more than a reproductive sac external to the host's body. They may occur in dense accumulations, but even single animals are large enough to be conspicuous. When they fall free from the host they often leave a characteristic lesion, which may heal in time. See Yamaguti (1963) and Hogans (1986), and references therein, for species descriptions and illustrations of these animals.

Hence, it would be difficult to miss either the parasite or the scars it leaves behind. Remarkably, there are apparently no records of parasitic copepods on marine turtles (host-parasite files of the Division of Crustacea, National Museum of Natural History, Smithsonian Institution, R. Cressey, pers. comm.; W. Hogans, in litt. May 1986).

Parasitic copepods may be preyed upon by disk-, or "sucker", fishes (Echeneidae) (Cressey and Lachner, 1970). There are seven species of these fishes, three of which are recorded on marine turtles: Echeneis naucrates L. (Ogran and Suddath in Yerger, 1965; Eckert and Eckert, 1988), Phtheirichthys lineatus (Menzies) (Cressey and Lachner, 1970) and Remora remora (L.) (Cressey and Lachner, 1970; Fretey, 1978; Eckert and Eckert, 1988). Specimens of R. remora which were associated with sharks are reported to have fed on parasitic copepods (Cressey and Lachner, 1970).

It could, thus, be argued that the presence of diskfish (R. remora in particular) on turtles is enough to keep the reptilian hosts "clean". However, the diskfish-turtle association is not invariably strong, and many large vertebrates that do have strong associations with diskfish (e.g., some sharks, billfishes, and whales) are frequently parasitized by copepods, even when they are accompanied by diskfishes. Simple predation by diskfish is not sufficient to explain the complete absence of parasitic copepods on marine turtles. Indeed, there is a record of a Remora (=Echeneis) remora [L.] affixed to a leathery sea turtle (Dermochelys coriacea [L.]), and the diskfish in turn had a Penella sp. parasitic on it (Petit, 1951).

If anyone has any knowledge of copepod parasites on marine turtles, they could perform a welcome service by making their observations known and setting the record straight. Until such information comes to light, we must wonder how marine turtles are able to avoid the attentions of these wide-ranging external parasites.

CRESSEY, R. and LACHNER, E. 1970. The parasitic copepod diet and life history of diskfishes (Echeneidae). Copeia 2:310-318.

DAILEY, M.D. and BROWNELL, R.L., JR. 1972. A check list of marine mammal parasites, p.528-589. In: Ridgway, S.H. (ed.), Mammals of the sea; biology and medicine. Charles Thomas. Springfield, Illinois.

ECKERT, K.L. and ECKERT, S.A. 1988. Pre-reproductive movements of leatherback sea turtles (Dermochelys coriacea) nesting in the Caribbean. Copeia 1988(3):400-406.

FRETEY, J. 1978. Accompagnement ... terre de tortues luths, Dermochelys coriacea (Linn‚) par des R‚moras. Rev. fr. Aquariol. 2:49-54.

HOGANS, W. 1986. Redescription of Pennella instructa Wilson, 1917 (Copepoda: Pennellidae) from the swordfish (Xiphias gladius L.). Can. J. Zool. 64:727-730.

PETIT, G. 1951. Capture d'une tortue luth ... La Nouvelle (Aude). Vie et Milieu 2(1):154-155.

YAMAGUTI, S. 1963. Parasitic Copepoda and Branchiura of fishes. John Wiley and Sons, Interscience. New York. 1104p.

YERGER, R.W. 1965. The leatherback turtle on the Gulf coast of Florida. Copeia 3:365-366.