Individual behavioral and neuronal phenotypes for arginine vasotocin mediated courtship and aggression in a territorial teleost.

The neuropeptide arginine vasotocin (AVT) is well known to modulate both aggression and affiliation, yet few studies relate individual behavioral state to a quantitative assessment of AVT distribution in the brain. Here, using a wild population of beaugregory damselfish, Stegastes leucostictus, we assess: (1) the effect of AVT on courtship, and (2) with reference to our previous study on AVT modulation of aggression in this species, the relationship between AVT-like immunoreactive (ir) fiber distribution in the forebrain's preoptic area and individual courtship and aggression levels. Exogenous AVT did not affect courtship, yet Manning compound, an arginine vasopressin (AVP) V1a receptor antagonist, significantly lowered but did not eradicate courtship. Consistent with AVT's known facilitation of aggression in this species, the density of AVT-ir fibers in the preoptic area was significantly negatively correlated to aggression. Our findings match similar behavioral and immunoreactive patterns of neuropeptide secretion in other taxa. Unlike aggression, preoptic AVT-ir fiber density was not significantly correlated to individual courtship levels. The results suggest a differential involvement of preoptic AVT neurons and/or their receptors in supporting the expression of aggression and courtship.