Parasitosis caused by Calyptospora in Pygocentrus nattereri (Characiformes: Serrasalmidae) from the Sacaizal Lake in the state of Amapá, Brazil

Abstract Parasites of the phylum Apicomplexa are among the main etiological agents of diseases in vertebrates and invertebrates, including humans and domestic animals. In the present study, 18 specimens of Pygocentrus nattereri (red piranha) captured in Lagoa do Sacaizal, municipality of Pracuúba, state of Amapá, were analyzed. Of these, 6 (33%) had whitish spots on their liver lobes. Clusters of Calyptospora sp. oocysts measuring 18.1 ± 0.5 (17.4-18.7) µm in diameter, with four pyriform sporocysts measuring 9.0 ± 0.45 (8.3-9.8) µm in length and 4.3 ± 0.50 (3.7-5.1) µm in width, each with two sporozoites. Histopathological evaluation indicated the presence of oocysts adjacent to blood vessels and in the hepatopancreas, promoting necrosis, degeneration, and tissue fibrosis associated with inflammatory infiltrate and melanomacrophage bodies. This is the first record of coccidia parasitizing P. nattereri.