Biology and behavior of Eigenmannia vicentespelaea, a troglobitic electric fish from Brazil (Teleostei: Gymnotiformes: Sternopygidae): a comparison to the epigean species, E. trilineata, and the consequences of cave life

Abstract

We compared the behavior, including spatial distribution, reaction to stimuli, activity phases, and agonistic interactions, as well as diet and reproduction, of the troglobitic Eigenmannia vicentespelaea and that of its epigean relative, E. trilineata, both from São Domingos karst area, central Brazil. We utilized ad libitum underwater observations, complemented by physicochemical water variables, habitat descriptions, and collections of specimens. Differences in behavioral aspects include the absence of cryptobiotic habits and an extended spatial and temporal activity in E. vicentespelaea that were not present in E. trilineata, and the foraging angle, which was approximately 30° in E. vicentespelaea and 90° in E. trilineata. The agonistic behaviors recorded for the troglobitic E. vicentespelaea could be related to the preservation of a character state that is present in its epigean relatives. Eigenmannia vicentespelaea and E. trilineata might be considered benthophagous invertivores, similar to other Eigenmannia electric fishes, with no evidence of seasonality in the volume and diversity of prey items in their stomachs, suggesting that there is a food spectrum common to the two species. Both epigean and troglobitic Eigenmannia fish from Goiás reproduce during the dry season, with no indication of reproductive peaks during this period.