Territoriality and agonistic behavior of subterranean Copionodontinae catfish (Siluriformes: Trichomycteridae) from Brazil

Abstract

Aggressive behavior may increase or decrease in troglobitic fishes, compared to epigean ones. Herein, we present the agonistic behavior repertoire and the causes that determine the dominance of two Brazilian cave catfishes: Glaphyropoma spinosum and putative undescribed Copionodon species. Both belong to Copionodontinae group, a small basal Trichomycteridae subfamily, and coexist in sandstone caves from Chapada Diamantina, northeastern Brazil. The results were compared with those exhibited by an epigean and syntopic species, Copionodon pecten. The fishes were paired and filmed until dominance was established; frequency of attacks was quantified and statistically analyzed. Cave copionodontine is one of the most hostile among subterranean fishes, with high frequency and complexity of aggressive components, including five new behavior components. Determinant factors for establishing dominance are body size, physical strength, and territoriality. Dominance is probably maintained by avoidance behavior by the subordinate and continuous attacks by the dominant. They are highly intolerant to conspecific, which may be a consequence of territoriality or feeding context. Two hypotheses may explain the agonistic behavior of cave species: (1) It is the maintenance of their ancestral behavior, being plesiomorphic in relation to the remaining Trichomycteridae subfamilies, corroborated by phototactic and spontaneous behavior; (2) It is an autapomorphy for Copionodontinae, due to new evolutionary acquisitions. The epigean C. pecten, in contrast, is much less aggressive, and the high tolerance to conspecific and the absence of accentuated territoriality may be explained by the food and/or space abundance in its natural habitats.