Austrodiplostomum compactum is a digenetic trematode whith metacercariae that occur in the eyes of a wide variety of fish species. In Brazil, A. compactum metacercariae have been reported in many fish species, but there are only a few studies in the Amazon region. Due to the lack of information in the Amazon, the aim of this study was to report the occurrence of A. compactum metacercariae in the eyes of 15 specimens of Plagioscion squamosissimus from the Lake Catalão, in Amazonas, Brazil. Fishes were collected using gill nets placed randomly in the lake, euthanized in a field laboratory, and had their eyes dissected and examined under a stereomicroscope. A total of 801 metacercariae were registered infecting the eyes of the hosts with a parasitic prevalence of 100%. There was a significant positive correlation between the number of metacercariae recorded and the standard body length of fishes. No significant correlation was found between the number of metacercariae and the weight and relative condition factor (Kn) of the hosts. Values of the variance-to-mean ratio and Green's index suggested an aggregate distribution of the parasites in the hosts, with a low degree of aggregation. This is the first report of occurrence of A. compactum parasitizing a fish in the Lake Catalão.

A new nematode species, Philometra nattereri n. sp. (Philometridae), is described from female specimens found in the oculo-orbits and nasal cavity of the red piranha Pygocentrus nattereri Kner (Characiformes: Characidae) from five lakes in Central Amazonia, Brazil, collected in 2008 and 2009 (overall prevalence 12%, intensity 1-3 nematodes per fish). Based on light and scanning electron microscopical examination, the new species differs from most other congeners parasitising freshwater fishes in that its oesophageal gland extends anteriorly far anterior to the level of the nerve-ring, in the presence of 14 small cephalic papillae arranged in two circles and in having two minute caudal projections. This is the first species of Philometra Costa, 1845 reported from fishes of the family Characidae and the second valid species of this genus parasitic in freshwater fishes of Brazil and South America.

El presente estudio investigó la presencia de helmintos en filetes de la piraña roja, Pygocentrus nattereri (Kner, 1858), alertando sobre un posible potencial zoonótico de su consumo en la forma in natural. Fueron examinados 40 peces capturados en lagos de varzea del Río Solimões, localizados entre los Municipios de Coari y Manaus en la Amazonía Central, Brasil. Todos los peces analizados fueron adultos y presentaban quiste amarillos en la musculatura del filete. Fueron encontrados 69 quistes e identificadas las metacercárias de las especie Clinostomum marginatum (Braun, 1899) (66 quistes) y Austrodiplostomum compactum (Lutz, 1928) (3 quistes). El análisis demuestra una mayor susceptibilidad de P. nattereri para metacercárias de C. marginatum. El hecho de haber sido encontradas metacercárias en filetes de P. nattereri, genera una situación de riesgo, remitiendo la preocupación en cuanto a su consumo en la forma cruda, no debiendo ser consumido sin una adecuada inspección, procesamiento y congelamiento, considerando que el cebiche es un alimento bastante consumido, principalmente en la región fronteriza del Alto Solimões en la Amazonía Occidental.

Between March and October 2008, 355 specimens of Pygocentrus nattereri were collected from the lowland lakes of Central Amazonia, Brazil, to study their nematode fauna. A total of 1.116 specimens of Nematoda were collected, belonging to six species. Procamallanus (Spirocamallanus) inopinatus was the species with the highest parasite indices. Larvae of Anisakis sp. have zoonotic potential and were found parasitizing the intestine and liver of Pygocentrus nattereri. Some of these nematode species were new records for the host P. nattereri. The diversity of nematodes that use P. nattereri as a host indicates the important role of this fish species in the maintenance of these six nematode species in the lowland lakes of Central Amazonia.