Clarias gariepinus is a fish from North of South Africa and was later introduced in several countries, including Brazil. The present study aimed to describe the first report of Diplostomidae metacercariae in C. gariepinus in Brazil. For this, 30 C. gariepinus were captured in a lake in the city of Campos dos Goytacazes, RJ, Brazil. Fishes were euthanized using freezing and necropsied for collection of parasites. The organs were dissected and analyzed for the presence of parasites that were processed for light and scanning electron microscopy. Trematodes were stained with Semichon’s Carmine and Gomori’s Trichrome, observed and schematized under a light microscope with image analysis software. A total of 190 trematodes were collected from the gills, suprabranchial organs, heart, stomach, intestinal mesentery, liver and body cavity of the fish. The parasites had a foliaceous body divided by a discrete constriction, without genital primordia, and a holdfast organ present at the posterior region, typical of metacercariae of the family Diplostomidae. It was classified as the 'Diplostomulum' morphotype, based on the morphology of the reserve bladder structure. This is the first report of the metacercariae of Diplostomidae parasitizing C. gariepinus in the Americas. This fish acts as an intermediate or paratenic host of this digenean in Brazil.
The genus Anableps is composed of species Anableps anableps, Anableps dowi, and Anableps microlepis. These fishes are tropical and usually live on the surface of brackish water, being popularly known as four-eyed-fishes due to the presence of prominent eyes and a pupil split horizontally. A. anableps and A. microlepis are considered as sister species that live in sympatry in South America. A. dowi, however, is restricted to the Pacific Ocean (Central America) and is considered the most primitive species of this genus. The aims of this study were to investigate the presence of endoparasites in A. anableps from the Parnaíba's Delta and characterize them morphologically. During the necropsy, larvae of Contracaecum sp. in the third larval stage (L3) were collected from the pancreas of A. anableps, but no endoparasites were observed in other organs. The worms had a cuticular tooth and excretory pore located at the anterior end, a thread like body, whitish color, and without distinction of sex. The length of the ventricular appendix of the larvae was much greater than in other studies. This is the first report of endoparasitism in A. anableps and the first report of nematodes in four-eyed-fishes.
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