The agonistic behaviour of Pimelodella kronei, a troglobitic catfish from Southeastern Brazil (Siluriformes, Pimelodidae).

Blind pimelodid catfishes Pimelodella kronei from a karstic area in Southeastern Brazil, were paired in the laboratory to study the agonistic behaviour. P. kronei, a recent troglobite, displays an intense and complex aggressive behaviour, presenting dominance based primarily on size. This dominance is established after bouts of duration inversely proportional to the size difference between the opponents. The aggressive repertoire of these pimelodids is similar to that of other studied siluriforms, and consists of varied and articulate components that include oscillations, shoves and bites. Once dominance is established, the subordinates recognize and avoid immediately the dominants after body contact or close proximity. High level of aggressivity in the blind catfishes may be related to competition for food in the cave habitat, where agonistic interactions were frequently observed.