Gastrointestinal Helminthofauna of Mediterranean Elasmobranchs

Elasmobranchs (Chondrichthyes, Elasmobranchii) are exposed to a variety of gastrointestinal parasites acquired through the ingestion of infected prey. An increasing amount of evidence suggests the usefulness of parasitological information to elucidate aspects of the biology and ecology of sharks and rays, to inform the correct management and conservation of their stocks and the appropriate husbandry of captive specimens. This study aims to identify at the morphological and molecular level the helminth parasites found in the stomachs and intestines of various elasmobranchs accidentally caught by Mediterranean fisheries, with the aim of updating and providing new information on the parasitic fauna of these species. Specimens of smooth-hound <i>Mustelus mustelus</i>, blackspotted smooth-hound <i>Mustelus punctulatus</i>, blue shark <i>Prionace glauca</i>, spiny dogfish <i>Squalus acanthias</i>, lesser-spotted dogfish <i>Scyliorhinus canicula</i>, pelagic stingray <i>Pteroplatytrygon violacea</i> and Mediterranean starry ray <i>Raja asterias</i> were examined. The parasitological examination allowed us to identify the nematode <i>Acanthocheilus rotundatus</i> in the two species of smooth-hounds analyzed, the tapeworm species <i>Scyphophyllidium exiguum</i>, <i>S. prionacis</i>, <i>Anthobothrium caseyi</i> and <i>Nybelinia indica</i> in <i>P. glauca</i>, the nematodes <i>Hysterothylacium aduncum</i> and <i>Proleptus obtusus</i> in <i>S. acanthias</i> and <i>S. canicula</i>, respectively, and finally the nematode <i>Pseudanisakis rajae</i> and the tapeworm <i>Nybelinia</i> sp. in <i>Raja asterias</i>. Some observations represent new reports at a geographical level, in particular, those on <i>A. caseyi</i> in <i>P. glauca</i> and <i>H. aduncum</i> in <i>S. acanthias</i> from the Adriatic Sea, or first host records, such as <i>S. exiguum</i> and <i>N. indica</i> in <i>P. glauca</i> or <i>P. rajae</i>. in <i>R. asterias</i>. The results of this survey represent a contribution to broadening the knowledge of the parasitic fauna of these elasmobranchs in the Mediterranean Sea. From more in-depth future studies, it will be possible to reach more solid evidence and general conclusions on aspects relating to the biology, ecology, and health of the investigated species, offering useful information for their conservation and management.