Histopathology of the infection by Perkinsus sp. in three clam species (Ruditapes decussatus, R. philippinarum and R. pullastra) from Galicia (NW of Spain)

Abstract

In this study, we have determined the histopathology of the infection by the protozoan parasite Perkinsus atlanticus in three exploitable clam species (carpet-shell clam Ruditapes decussatus, Manila clam R. philippinarum, and the species R. pullastra) from Galicia (NW of Spain). In histological preparations from infected animals, typical mature trophozoites of Perkinsus, containing lipid droplets and vacuole but no vacuoplast, were observed. The trophozoites were usually in groups surrounded by a light halo. Pre-palintomic tomonts, as well as palintomic tomonts with a variable number of daughter cells, were also present in the host tissues. Less frequently, immature trophozoites with an undifferentiated cytoplasm were observed. The presence of P. atlanticus cells was always associated with a strong hemocytic infiltration of the surrounding tissues. Occasionally, the parasite cells were internalized by granular hemocytes. The morphology and distribution of the P. atlanticus were similar in the three clam species studied, this being the first time that R. pullastra from Galicia has been found infected by P. atlanticus. The morphology of the parasite's life cycle stages and the histopathology of the infection resemble those reported on other species of the genus Perkinsus.