Balaenophilus manatorum in Debilitated and Bycatch-Derived Loggerhead Sea Turtles Caretta caretta from Northwestern Adriatic Sea

SIMPLE SUMMARY: Sea turtles, Caretta caretta, are hosts for several animal and algal organisms which live on their body surface and develop a symbiotic association with them which can range from mutualistic to parasitic, depending primarily on the species. The copepod Balaenophilus manatorum has developed a true parasitic association in that, while exploiting turtle’s skin keratin as a food resource, it may be responsible for cutaneous lesions whenever the equilibrium host-parasite is lost. Studies reporting B. manatorum as a component of epibiotic communities of turtles are still sparse in the literature, and little is known about its distribution in the Mediterranean Sea. This study aimed to investigate its presence in C. caretta ranging in the Northwestern Adriatic Sea and to investigate the effects of Debilitated Turtle Syndrome (DTS) on the turtle–parasite equilibrium. The results of this study indicate that the copepod is a common epibiont of turtles feeding in this region and that individuals suffering from DTS are more frequently parasitized and have higher copepod burdens. Appropriate attention should be given, in debilitated animals, to proper treatment against external epibionts, taking into account the eventual co-presence of true parasites. ABSTRACT: Balenophilus manatorum (Copepoda: Harpaticoida) is one of the few components of the epibiontic fauna of Caretta caretta that show a “true” parasitic association with their host. From rrosive to ulcerative cutaneous lesions may seldom appear as a consequence of the copepod feeding on keratin on turtles’ skin. Debilitating Turtle Syndrome (DTS) is the final outcome of a chronic insufficient assumption of nutrients, generally occurring with the impairment of immune functions and high epibiota burdens. In this survey, the presence of B. manatorum in C. caretta from the Northwestern Adriatic Sea was investigated and the relation between infection indices and the co-occurrence of DTS was studied. Clinical examination was performed at the time of rescue, including routine hematological assessment; external parasites were isolated mechanically from turtles’ skin and morphologically identified through observation with an optic microscope and SEM. Ten turtles were classified as affected by DTS, all of them being small juveniles with typical clinical and clinicopathological presentation. A higher prevalence, abundance, and density of infection were found in turtles affected by the syndrome. The presence of massive skin coverage by the burrowing barnacle Pletylepas hexastylos prevented a proper evaluation of the pathology associated with B. manatorum in turtles affected by DTS. In any event, eventual skin damages caused by the parasite may represent a port of entry for secondary infections in such immunocompromised animals. Therefore, infection by B. manatorum should not go overlooked in debilitated turtles and should be opportunely treated.