Metazoários parasitos de um peixe detritívoro de lagos de várzea do rio Solimões, Pterygoplichthys pardalis (Castelnau, 1855) (Siluriformes: Loricariidae) e uma avaliação de seu uso como espécies bioindicadoras de efeito em mudanças ambientais na Amazônia

Abstract

Were analyzed 248 individuals of Pterygoplichthys pardalis caught in five lowland lakes of the Amazon. The mean fish length was 24.5cm ± 8.8 and the mean weight was 213.9g ± 102.6. The sampled lakes were: Baixio; Black; Ananá and Araçá on the river Solimões and São Tomé on the Purus river, located between the cities of Manaus and Coari in the state of Amazonas. Necropsies were performed in the field and the organs were fixed. The qualitative descriptors of the parasite populations were: number of individuals, stage of maturation and dominance of each species and their importance. A total of 1,635 parasite specimens from five taxa were collected: Monogenoidea (785); Digenea (795), Cestoda (1), Acanthocephala (50) and Copepoda (4). Four species parasitized the gills: three of Monogenoidea: Unilatus brevispinus, Heteropriapulus heterotylus and Trinigyrus mourei and one of Copepoda, Therodamas elongatus. Six species of Digenea occurred: metacercariae of Diplostomum sp., Austrodiplostomum compactum, Odhineriotrema microcephala and adults of Megacoelium spinispecum, M. spinicavum and Kalitrema kalitrema. The metacercariae parasited the eyes, stomach, gonads and surface of internal organs. A larva of Proteocephalidea was found on the surface of the intestine. A species of Acanthocephala Gorytocephalus elongorchis inside the intestine. Digenea was the most diverse taxa with 50% of the species, followed by Monogenoidea 25%. Among the components of the P. pardalis infracommunity, two species were the most abundant during the four hydrological periods: Monogenoidea, U. brevispinus in flood (56.1%) and ebb (81.6), and Digenea, Diplostomum sp . (73.2%) and dry (93%). Of the twelve species found in the community component: Diplostomum sp. and U. brevispinus were the species that parasitized the largest number of hosts and had the highest parasitological indexes. Unilatus brevispinus was the most abundant species. Diplostomum sp. was the species that fulfilled the requirements proposed by Overstreet (1997) to be an environmental bioindicator species.