Candiru

Abstract: A historia natural de Pygidianops sp. (Trichomycteridae, Glanapteryginae), uma especie nao descrita de candiru de vida livre, foi estudada com base em observacoes de individuos que habitam um igarape de terra-firme da Amazonia Central. Esses peixes permanecem todo o tempo mergulhados na areia do fundo do igarape, e nao foram observados emersos em ambiente natural. Os individuos da especie se alimentam de pequenos invertebrados psamofilos, especialmente larvas de Chironomidae e copepodos Harpacticoida, que provavelmente sao capturados atraves de succao por meio de caca ativa em meio a areia. Em relacao a reproducao, femeas maduras foram encontradas durante um ciclo sazonal completo, e apresentaram poucos ovocitos de tamanho proporcionalmente grande. A presenca/ausencia e abundância de Pygidianops sp. ao longo do igarape parece ser influenciada por uma combinacao de fatores ambientais, como declividade do banco de areia, velocidade da corrente, profundidade, composicao granulometrica da areia e, especialmente, o fluxo da agua entre as particulas de areia. Outras caracteristicas bioticas, como a presenca de presas distribuidas em manchas de substrato, possivelmente influenciam a ocupacao do substrato por Pygidianops sp.%%%%The natural history of Pygidianops sp. (Trichomycteridae, Glanapteryginae), an undescribed species of free-living candiru, was studied based on observations of individuals inhabiting a forest stream in Central Amazon. The fish remains buried in the sand of the bottom of the stream all the time, and were never observed emersed during our field observations. The individuals feed on small psammophilous invertebrates, especially mosquito larvae (Chironomidae) and sand-crawling copepods (Harpacticoida), which are probably captured by suction through active hunting amidst the sand grains. Regarding the reproduction, mature females were found all over the year, and presented few and proportionally very large oocytes. The presence and abundance of Pygidianops sp. along the stream seems to be influenced by a combination of local environment factors, such as the sand bank slope, the water flow, channel depth, grain size composition of the sand and, especially, the water flow inside the sand particles, which is very difficult to evaluate. Other biotic characteristics, such as the apparently patchy distribution of prey, possibly influence the occupation of the substrate by individuals of Pygidianops sp.