Características ecológicas que determinam o uso de habitats subterrâneos por peixes em um carste neotropical

Abstract

The aim of this research was to increase the knowledge on Brazilian cavefish characteristics, from genetic to behavioral aspects. Considering that the upper Tocantins river basin has a high diversity of cavefishes, this research also aimed to understand which characteristics can enable fishes to occur in caves and whether there are differences in habitat use in two different ecomorphs from a same species (troglomorphic and non troglomorphic). A compilation of the species occurring in the upper Tocantins river basin was made, considering which species occurs in the epigean or hypogean or in both environments, and some of their characteristics (morphological and behavioral) that may influence their occurrence in the subterranean environment, considered as environmental filter. To understand the habitat use by cavefishes, a study was conducted with ecomorphs of Ituglanis that inhabits a hypogean stream in the same basin. First, genetic analyzes were performed to verify if the ecomorphs (troglomorphic and non troglomorphic) belong to the same species. In the field, the habitat variables were measured. The results suggested, for the first objective, that Siluriforms and Gymnotiforms are significantly related to the presence in caves: they are either the most abundant in the hypogean, possibly due to common pre-adaptive characteristics between them. The genetic analyses showed that both ecomorphs belong to the same species with phenotypic plasticity and are either Ituglanis passensis, a cavefish species that occurs in another cave located more than 60 kilometers. The habitat use results demonstrated differences in preferences between the two ecomorphs. The troglomorphic organisms seem to be more specialized to cave conditions than those non troglomorphic. It was concluded that although some characteristics do not influence the fish occurrence in the caves others are determinant (pre-adaptive traits). Furthermore, specialization in the hipogean environment can also be related to the habitat use. This research reinforce the necessity for further studies on cavefishes in the upper Tocantins river basin emphasizing genetic and systematic works for fish’s conservation and better decisions to protect this region with the largest diversity of cavefishes in Brazil.