Ocorrência de ectoparasitos monogenéticos em brânquias de Rhamdia branneri Haseman,1911 (Siluriformes: Heptapteridae) de dois riachos do Baixo Iguaçu

Abstract

In Brazil, most of the urban sewage and materials from the manholes of the streets are channeled into rivers and streams resulting change on physico-chemical factors of the water and turning the fish susceptible to the parasite establishment. The objective of this study was to analyze the occurrence of ectoparasites on gills of Rhamdia branneri in two neotropical streams of the Iguaçu River Basin, one with natural features preserved and other in an urban area. Each stream was sampled over a length of 40 meters long, also being collected data about the physical habitat. The total sample was 25 fish collected by electrofishing, anesthetized with benzocaine (10%), stored in individual plastic bags and kept in a cooler with ice to destination for further analysis of the gills. It was performed the mann-whitney “u” test, to check the influence of the host sex on the number of parasites found in urban stream. The density of parasites on the fish was compared between the streams by analysis of variance. Among the physical and chemical variables, only the electrical conductivity proved uneven. It was found that all the fish were small. In the preserved stream, the prevalence of infected fish was 45.45%, and 78.57% in urban. The density of parasites per fish was significantly different between the two environments, being higher in urban stream, showing that these organisms may be favored by ecological factors. There was no significant difference from the number of parasites found in males and females host in the urban stream. Two species of Monogenea from the urban stream were identified, being Aphanoblastella mastigatus and A. Juizforense. In conclusion, it is important to add to the parasitological studies, information from abiotic factors in order to verify the relationship between them.