Spiral Valve Parasites of Selected Tropical Pelagic Elasmobranchs from the Western North Atlantic Ocean

Concerns regarding population status of many elasmobranchs have prompted investigations into less obvious sources of declines, such as morbidity due to parasites. Endoparasite (internal) loads in the elasmobranch spiral valve may be a source of such unaccounted mortality and morbidity by both inhibiting nutrient uptake and stimulating inflammatory responses within the gastrointestinal tract in the host. Spiral valves of the night shark ( Carcharhinus signatus , n=16), silky shark ( Carcharias falciformis , n=18) and pelagic stingray ( Pteroplatytrygon violacea , n=99) were obtained opportunistically from pelagic longline operations. Each species had varying rates of parasitization: pelagic stingray 29%, silky shark 77%, and night shark 92%. Total spiral valve parasite loads were compared against the total length, weight and sex of the host; however, no relationship was observed between these factors. A total of 133 elasmobranch hosts were examined, yielding over 800 individual parasites. The majority of parasites were cestodes (92% pelagic stingray, 93% silky, 99% night), although trematodes (5% pelagic stingray, 2% silky, 1% night), nematodes (1% silky), and acanthacephalans (3% pelagic stingray and 4% silky) were also represented throughout the samples. There are over ten families of cestodes represented throughout the samples, two families of trematodes, one family of nematode and two families of acanthacephalans. Site specification was not examined for this research. Parasites were not shown to be host specific. These results establish baseline values for expected spiral valve parasite load and species compositions for pelagic shark and stingray hosts.