| Communication among African weak-electric fish (Mormyridae) involves alterations of their electric organ discharge rhythmicity. The electric behavior of one fish can affect the electric signalling of another fish. However, progress in determining the social significance of these alterations has been hindered by a lack of a comprehensive description of the fish's social behavior. This investigation of the agonistic behavior of Gnathonemus petersii will contribute a behavioral catalogue, and will also examine the role of the electric organ discharge and vision in eliciting and maintaining social behavior.;On the basis of the interactions between intact fish, a baseline catalogue of 17 motor acts was established. Several of the socially directed behaviors were previously observed in mormyrids exploring novel objects. Thus, in the present context, these behaviors were termed "social probing".;The surgical manipulations resulted in the following: Electrically silent intruders elicited less social probing than intact intruders, but were attacked more frequently by sighted residents. Electrically silent residents tended to be less aggressive than intact. Silent intruders were less effective in eliciting chases and attacks from blind residents than from intact residents. Except for their reduced rate of attack, blind residents, with intact electric organs, were indistinguishable from intact residents in the presence of intact intruders. Blind-silent residents rarely chased or attacked intruders, and then only intact ones.;Butt and lateral display were accompanied by stereotypic discharge patterns, which were characterized by short interdischarge intervals of nearly constant duration. Such conspicuous patterns could be useful in electrocommunication. All other observed behaviors were associated with variable discharge patterns, characterized by a wide range of interdischarge intervals.;"Resident" fish, following three days of adaptation to an experimental tank, were presented with ten different stimulus fish, "intruders", one at a time. The experimental manipulations included surgical interference with the resident and/or the intruder. One or both members of an interacting pair were either intact, electrically "silent" (through spinal sectioning), blind, or both blind and electrically silent.;The results illustrate the importance of both electric organ discharges and vision in mediating aggression in African freshwater mormyrid fish. |
