Helminth component community of the loggerhead sea turtle, Caretta caretta, from Madeira Archipelago, Portugal

The helminth fauna of pelagic-stage loggerhead sea turtles, Caretta caretta, is still poorly known. Here, we describe the helminth-component community of healthy, free-ranging juvenile loggerhead sea turtles captured in the waters around Madeira Island, Portugal. Fifty-seven were used in this study. The esophagus, stomach, intestine, liver, gallbladder, spleen, kidneys, trachea, bronchi, urinary bladder, heart, left and right aortas, and coelomic cavity were macroscopically inspected; organs and tissues were removed and washed through a sieve. A search for parasites was made using a stereoscopic microscope; recovered parasites were fixed and stored in 70% alcohol until staining and identification. Prevalence, mean intensity, and mean abundance values were recorded. In total, 156 parasite specimens belonging to 9 species were found: nematodes included Anisakis simplex s.l. (larvae) and an unidentified species; digenetic trematodes present were Enodiotrema megachondrus, Rhytidodes gelatinosus, Pyelosomum renicapite, and Calycodes anthos; acanthocephalans included Bolbosoma vasculosum and Rhadinorhynchus pristis; a single cestode, Nybelinia sp., was present. Parasite infections were found to have both low prevalences and intensities. Possible reasons for this include the oligotrophic conditions of the pelagic habitat around Madeira; a 'dilution effect' because of the vastness of the area; and the small size, and thus ingestion rate, of the turtles. Results are discussed in terms of the various turtle populations that may use the waters surrounding Madeira. This work provides valuable information on the parasite fauna of a poorly known stage in the life of loggerhead sea turtles, thereby filling a fundamental gap with regard to features of the parasite fauna in this species.