Metazoan endoparasites diversity of Pseudoplatystoma corruscans (Siluriformes: Pimelodidae) as an indicator of environmental alterations on a tropical aquatic system

摘要

The aim of the present study was to detect the alterations of Pseudoplatystoma corruscans parasite infracommunity structure, after the construction of the Porto Primavera dam on the high Paraná River floodplain. The execution of this research was based on 119 host specimens collected between March 2011 and September 2012, and the results were compared to studies performed on periods before the reservoir’s construction, when 110 fishes were collected between March 1992 and February 1993. Five parasite species still remain on the environment, despite the environmental modifications: Choanoscolex abscissus, Spasskyelina spinulifera, Nomimoscolex pertierrae, Harriscolex kaparari and Contracaecum sp 2. The Berger-Parker dominance index, calculated to the parasite fauna of 1992, did not show the dominance of any species, while, on the present days, this same index accused the dominance of Nomimoscolex pertierrae (49%) and Choanoscolex abscissus (50%). The present study reports the disappearance of Megathylacus travassosi, Contracaecum sp. 1, Contracaecum sp. 3, Procamallanus (Spirocamallanus) sp. and Cucullanus pseudoplatystomae, suggesting the possibility of a local extinction or a host switch of these species. It has also been registered an Acanthocephala specimen, a genus not observed on this host yet. The results here presented show that the antropic influences on natural systems alter the environmental conditions, what is reflected on the richness and diversity parasite levels.