Metacercariae of Austrodiplostomum compactum (Trematoda, Diplostomidae) in non-native fish species in Brazil: a possible explanation for the high rate of parasitic infection

Abstract

Metacercariae of Diplostomidae are widely distributed in America and may cause diplostomiasis, an ocular disease in fi shes. The aim of this study is to report the occurrence of metacercariae of Austrodiplostomum compactum in Plagioscion squamosissimus (non-native fi sh species) from Nova Avanhandava Reservoir, Tietê River, Brazil and an explanation for the high infection rates with this parasite in the Paraná River Basin is proposed. Eyes of 70 hosts were examined, the metacercariae were preserved and identifi ed. The prevalence (P), mean intensity of infection (MII) ± standard deviation, mean abundance (MA) ± standard deviation, were calculated and a bibliographic review was performed. There was no difference in parasitism between male and female hosts. The values of P = 80%, MII = 21.55 ± 3.25 and MA = 17.24 ± 2.91 were high, as in most studies in areas where P. squamosissimus were introduced, while these values were low in areas of natural occurrence. This may be explained by the genetic susceptibility of the host to the parasite. The entire population of P. squamosissimus from the Upper Paraná has been founded by a few specimens, resulting in very low genetic variability. Consequently, the population may be highly susceptible to A. compactum.

Fauna of metazoan parasites of Pterygoplichthys pardalis (Castelnau, 1855) sold at fairs in the city of Manaus, state of Amazonas, Brazil

“…In South America, this disease is caused by species belonging to genus Austrodiplostomum (Szidat & Nani, 1951) (Ramos, Pagliarini, Franceschini, & Silva, 2020). According to Vital, Morey, Pereira, and Malta (2016) (Thatcher, 1986) 30/2 6.7 1 0.06 1 Gills 2 there are Brazilian Amazon fish species including P. pardalis, which have been recorded as A. compactum hosts.…”

Morphological and molecular characterization of Austrodiplostomum compactum metacercariae in the eyes and brains of fishes from the Ivaí River, Brazil

“…Despite the wide distribution and increasing number of occurrences of Austrodiplostomum spp. in fishes (Pelegrini et al, 2019;Acosta et al, 2020;Campos et al, 2020;Ramos et al, 2013Ramos et al, , 2020 in Brazilian rivers, there are still sites where studies are scarce, such as the Ivaí River, located entirely in the state of Paraná, Brazil, and is an important tributary of the Paraná River basin.…”