Unusual Localization of <i>Pennella</i> Sp. in Swordfish (<i>Xiphias gladius</i>) Hearts

Abstract

The genus <i>Pennella</i> comprises hematophagous parasites of marine aquatic species, including cephalopods, marine mammals, and pelagic fish. Nine species have been officially included in the genus <i>Pennella</i> plus another six <i>species inquirendae</i>. They are most often found in the host’s musculature, without penetrating internal organs. For the present study, 83 hearts from swordfish (<i>Xiphias gladius</i>) caught in the Mediterranean Sea were sampled and immediately fixed in formalin for histopathological analysis. In total, 10 (12.05%) hearts were found to be parasitized by copepods of the genus <i>Pennella</i>. Macroscopically, there was mild-to-severe fibrinous pericarditis with atrial wall thickening and multiple parasitic nodules. Histologically, the parasitic nodules were surrounded by an inflammatory-necrotizing reaction. Parasitic infestation by <i>Pennella</i> spp. is common in pelagic fish and in swordfish, in particular. Here, however, we report atypical cardiac localization. A future area of focus is the evaluation of cardiac <i>Pennella</i> spp. infestation by histopathology and genetic identification of the parasites.