Forebrain arginine vasotocin correlates of alternative mating strategies in cricket frogs

In cricket frogs, Acris crepitans, sexually active males can switch between calling and noncalling (satellite) mating strategies and injections of the neuropeptide arginine vasotocin (AVT) stimulate calling behavior. We repor t here that this behavioral variation of animals under field conditions is associated with variations in AVT-immunoreactive (AVT-ir) staining in disti nct brain nuclei. In both calling and satellite males, one AVT-ir brain reg ion was found in a continuous string of cells between the medial amygdala a nd the nucleus accumbens (ACC). Satellite males possessed significantly mor e AVT-ir staining in the brain (cells and fibers) than calling males at the level of the ACC, although not in the medial amygdala. This difference in AVT-ir staining in the ACC can, in part, be explained by differences in the density of staining within the cells and in cell size. In addition, satell ite males had significantly higher AVT-ir staining in the fibers medial to the ACC than calling males. Because other studies have demonstrated that AV T stimulates calling behavior, a plausible hypothesis is that calling males are releasing more AVT from neurons in the ACC, depleting reserves within the cells, and that the released AVT elicits calling behavior. AVT immunore activity levels are also higher in the ACC in both calling and satellite ma les than in female cricket frogs, which do not call. Satellite males may th erefore have AVT reserves that might allow them to call depending on the so cial conditions. (C) 1999 Academic Press.