Metacercariae of Clinostomum Leidy, 1856 (Digenea: Clinostomidae) infecting freshwater fishes throughout Brazil: infection patterns, parasite–host interactions, and geographic distribution

Abstract

ABSTRACT This review investigated information about metacercariae of Clinostomum Leidy, 1856 published over 91 years (1928 to 2019) to search for infection and geographic distribution patterns of this digenean species in freshwater fish from Brazil. The present study used 101 samples from 60 fish species of different families distributed in Characiformes, Siluriformes, Cichliformes, Gymnotiformes, Cypriniformes, Cyprinodontiformes, and Synbranchiformes. The greatest number of parasite–host associations were found for Cichliformes species of the Cichlidae family. Metacercariae of digeneans that belonged to four species of Clinostomum were found, with Clinostomum marginatum and Clinostomum complanatum (68.7%) the dominant species, whereas 22.2% of parasites were allocated only to the genus Clinostomum. There was variation in prevalence, intensity and abundance of Clinostomum spp. in host fish, and infection sites included internal and external organs (e.g. intestine, stomach, operculum, muscle, mouth, heart, gills, body cavity, fins). There was similarity in prevalence, intensity, and abundance of Clinostomum spp. in detritivorous, omnivorous, and piscivorous host fish. Clinostomum metacercariae are distributed in the Amazon, Paraná River, São Francisco, Uruguay, Atlantic North and South, and Southeast basin systems, whereas C. marginatum and C. complanatum have distribution patterns limited to hydrographic basins of different regions. Clinostomum spp. have a cosmopolitan distribution and parasitize a diversity of host fish, and the present study constitutes the most extensive survey regarding these digeneans in fish throughout Brazil.