Adaptações morfológicas do trato digestório do peixe neotropical Steindachnerina notonota (Characiformes, Curimatidae) ao hábito alimentar detritívoro

Abstract

Detritivory is the common freshwater fishes, especially in the Neotropical region, and for many species are scarce information about the digestory tract, as is the case of the species Steindachnerina notonota, in which, it has ecological importance as links in the food chain, serving of feed for carnivorous fishes, and acting in the depuration of aquatic ecosystems subject to organic pollution. The objective of present study consists of analyzing the morphological adaptations of the digestory tract, of this endemic species of the caatinga, Brazilian semiarid region. Thus, 10 adult specimens were used (males and females), necropsied for macroscopic and microscopic analysis of the digestory tract. All structures were observed in the stereomicroscope. The organs were fixed in 10% formalin and submitted to hematoxylin and eosin staining, and PAS - periodic acid Schiff (gill rakers, epibranchial organ, esophagus, stomach, midgut and hindgut) and analyzed by light microscopy. The gill rakers were also fixed in 10% paraformaldehyde for analysis by scanning electron microscopy. The specimens analyzed had total length between 6,4 to 13 cm, standard length between 4,8 to 10,3 cm, and weight of 3,23 to 35,92 g. The structural adaptations in the digestory tract were: mouth of the terminal type; the particular complex bucopharyngeal; absent from tooth and tongue; it has three types of formats of gill rakers with mucous cells and taste buds; possess the epibranchial organ with its peculiarities; a mechanical stomach with highly developed musculature in the pylorus; and a very long and coiled intestine, which internally has exclusive helical fold. The morphological aspects of digestory tract of S. notonota are related to detritivore-ilyophago specialized feeding habit.