Resumo: A relação peso-comprimento (RPC) e dieta de um pequeno bagre trichomycterídeo, Cambeva guareiensis, foi estudada com base em 58 espécimes capturados no riacho Corrente, bacia do rio Guareí, São Paulo, Brasil. As análises de RPC mostraram valores de a variando entre 0,0097-0,0149 e de b entre 2,858-3,250. A análise da dieta mostrou que altas quantidades de insetos aquáticos (93,75% do total de itens) foram consumidas pela espécie. Além disso, não encontramos diferenças estatisticamente significativas quando comparamos a dieta entre os períodos seco e chuvoso. Nosso estudo contribui para o conhecimento da biologia populacional e ecologia alimentar de peixes trichomicterídeos em riachos brasileiros.

Abstract: The length-weight relationship (LWR) and diet of a small trichomycterid catfish, Cambeva guareiensis, was studied based on 58 specimens captured in Corrente stream, Guareí River basin, São Paulo, Brazil. LWR analyses showed values of a ranged from 0.0097 to 0.0149 and b from 2.858 to 3.250. The analysis of the diet showed that high amounts of aquatic insects (93.75% of total items) were consumed by the species. In addition, we found no statistically significant differences when comparing the diet between the dry and rainy periods. Our study contributes to the knowledge on populational biology and feeding ecology of trichomycterid fishes in Brazilian streams.

Abstract: Albinism is a genetic condition caused by an autosomal recessive gene that affects normal pigmentation in animals. In Neotropical freshwater fish fauna, albinism cases are extremely rare, with only 14 species recorded among more than 6000 described. Here, we describe the first reported case of albinism in the South American catfish Imparfinis mirini. The albino fish was collected in July 2016 with a seine net in a stream in southeast Brazil. Although albinism can decrease the chance of fish survival, the cryptic and nocturnal habits of this species and the low amount of piscivorous fish and birds in the stream may have favored its growth. Two possible explanations for the appearance of the albino fish are discussed: a genetic disorder caused by heavy metal contamination and the high endogamy rate in the fish population which could increase the chances of appearing deleterious genes.

Resumen: El albinismo es una condición genética causada por un gen autosómico recesivo que afecta a la pigmentación normal en los animales. En la fauna de peces de agua dulce neotropicales, los casos de albinismo son extremadamente raros, con solo 14 especies registradas entre más de 6000 descritas. Se expone el primer caso documentado de albinismo en el bagre sudamericano Imparfinis mirini. El pez albino fue recolectado en julio de 2016 con una red de cerco en un arroyo en el sureste de Brasil. Aunque el albinismo puede disminuir la probabilidad de supervivencia de los peces, los hábitos crípticos y nocturnos de esta especie y la baja cantidad de peces y aves piscívoras en los arroyos pueden haber favorecido su crecimiento. Se examinaron 2 posibles explicaciones para esta condición: un trastorno genético causado por la contaminación por metales pesados y la alta tasa de endogamia en la población de peces, que podría aumentar las posibilidades de aparición de genes deletéreos.