Biodiversidade de helmintos parasitos de peixes do Baixo Rio Doce, Brasil

Abstract

Studies involving the biodiversity of fish helminth parasites have expanded the knowledge on different aspects of host-parasite relationships involving these organisms. Such studies have revealed the potential of some helminth groups to act as bioindicators of environmental quality. In this context, the Doce River is an example of degraded environment involving contamination mining dam collapses in Mariana, Minas Gerais, in November 2015. Although studies on the helminth fauna of fishes can provide useful information about the environmental health, information on this topic are practically non-existent for this important Brazilian river. Therefore, the present study aims to contribute to the knowledge of the taxonomy composition of helminth parasites of fish in the Lower Doce River. For this purpose, fish samplings were carried out in the main channel of the Doce River at 3 regions located in the urban centers in the north of Espírito Santo State (Linhares, Colatina and Baixo Guandu) and three tributaries. The fish collected were necropsied, and the helminths found were fixed and subsequently processed for morphological study under light microscopy, scanning electron microscopy (SEM) and genetic analyzes. In total, 317 fish specimens from 34 species were analyzed, of which 109 (34.27%) were found infected with helminth parasites. The taxonomic studies carried out revealed the presence of 13 species of helminths (Cestoda, Trematoda and Nematoda) among the fish evaluated. Two species of cestodes, Proteocephalus macrophallus and Proteocephalus microscopicus were identified in Cichla kelberi. Among trematodes, three species of Diplostomidae (Austrodiplostomum compactum, Austrodiplostomum sp. and Dolichorchis sp.) were found in the eyes of different fish species. Additionally, metacercariae of Dolichorchis sp. is recorded for the first time in the country. Metacercariae with morphology compatible with Clinostomum dimorphum and Clinostomum sp. were found in different hosts, and the last one is compatible with unnamed isolates of this genus found in Argentina and Mexico. Metacercariae of Manteria sp. represent the first record of metacercariae of the family Acanthocolpidae in Brazil. Among nematodes, 3 species of the family Camallanidae, Procamallanus (Procamallanus) peraccuratus, Procamallanus (Spirocamallanus) inopinatus, Procamallanus (Spirocamallanus) sp., were found in different fish species. Are also proposed new records of Contracaecum sp. and Ichthyoris sp. in different hosts. The present study represents the first contribution to the knowledge of the helminth fauna of fish in the Lower Doce River and can serve as a basis for future studies related to the assessment of environmental impacts. Qualitatively, the data obtained demonstrate that despite previous contamination by mining wastes in the Doce River, several helminth species with a complex life cycle still occur in the evaluated region, pointing to the existence of ecological relationships related to parasite transmission processes.