Spontaneous behavior of basal Copionodontinae cave catfishes from Brazil (Teleostei, Siluriformes, Trichomycteridae)

Bianca Rantin,Maria Bichuette

doi:10.3897/subtbiol.16.5180

Abstract

Cave animals are particularly interesting due to their behavioral specializations, resultant from evolution in isolation. We present data from a spontaneous behavior study (spatial distribution and preference for microhabitats) of two troglobitic catfish from Brazil: Glaphyropoma spinosum and a new species of Copionodon. We compared the data with those obtained of a sympatric epigean species, Copionodon pecten. These Trichomycteridae species belong to a basal and apparently monophyletic subfamily – Copiono dontinae, endemic to Chapada Diamantina, central Bahia state, eastern Brazil. We observed the fishes in natural and laboratory conditions through ad libitum and focal animal methods. Each spatial behavioral category (hidden, bottom, midwater, surface and wall swimming and stationary in the bottom) was timed individually, with a sample of 12 specimens per species. Unlike most troglobitic fishes, cave copionodon tines tested herein did not extend exploratory behavior to midwater, with benthonic and thigmotacticrelated exploratory behavior. This behavior is possibly related to its feeding behavior specializations, strong territorialism and photophobic behavior. The epigean Copionodon species is also benthonic. The spatial behavior of the cave Copionodontinae could be interpreted as a retained and plesiomorphic characterstate in relation to other trichomycterid catfishes.

Highlights

Stygobites are organisms restricted to the subterranean aquatic environment, which had evolved isolated in a peculiar selective regime, distinct from that of their ancestrals: total absence of light, a tendency to environmental stability, lack of primary production and low energy intake (Culver 1982, Poulson and Lavoie 2000, Culver and Pipan 2009)
In order to understand whether the observed spontaneous behavior consist of specialization traits for Copionodontinae, we considered its basal phylogenetic position within Trichomycteridae clade
The strong cryptobiosis presented by the subterranean species Glaphyropoma spinosum is corroborated by field and laboratory observations, where only rarely the specimens were observed exposed, stationary on the aquarium bottom, and seldom exploring walls and water column

Summary

Introduction

Stygobites are organisms restricted to the subterranean aquatic environment, which had evolved isolated in a peculiar selective regime, distinct from that of their ancestrals: total absence of light, a tendency to environmental stability, lack of primary production and low energy intake (Culver 1982, Poulson and Lavoie 2000, Culver and Pipan 2009). Several specializations related to life in the subterranean environment have been reported in literature - autapomorphies, called troglomorphisms (Arnold 1994). These cave specializations include morphological troglomorphisms (for instance, reduction of eyes and melanic pigmentation and elongation of body and appendices) and behavioral ones (such as increase of midwater activity and reduction of photophobia, cryptobiotic behavior and circadian rhythms) (Trajano 2003). The spontaneous behavior is well studied for Brazilian troglobite fish Spontaneous behavior encompasses use of space, i.e., preference for microhabitats, spatial distribution (bottom, midwater or surface), burrowing, hiding and other behavior expressed in the absence of stimuli

Methods

Results

Conclusion