LEMA, S.C.*; NEVITT, G.A.; Univ. of California, Davis: Arginine Vasotocin Modulates Social Behaviors in a Death Valley Pupfish

Pupfishes in the Death Valley region inhabit remote pools and streams that have become isolated by the surrounding desert over the past 20,000 years. These aquatic habitats are ecologically diverse, and populations show considerable variation in social behaviors even without substantial genetic divergence. The social behaviors of pupfish, however, are responsive to the immediate ecological conditions that populations are experiencing. This plasticity suggests that population differences in social behavior might be explained as a physiological response of individuals to the unique environments they inhabit. As a first step toward exploring the proximate basis of population variation in pupfish behaviors, we are studying how arginine vasotocin (AVT) affects agonistic and reproductive behaviors in the Amargosa River pupfish (Cyprinodon nevadensis amargosae). AVT and its homologue arginine vasopressin (AVP) modulate social behaviors in a variety of taxa and recently have been implicated to underlie species differences in behavior. We intraperitoneally administered AVT (0.1 μg, 1 μg, and 10 μg per g body wt) and an antagonist to the V_1a receptor for AVP (Manning compound; 2.5 μg per g body wt) to C. n. amargosae males. Our results from this investigation show two general trends: 1) Males treated with AVT initiated fewer aggressive interactions in a dose-dependent manner than males given a saline control, and 2) Males treated with Manning compound showed a small increase in the initiation of aggressive interactions. The opposing effects of AVT and the receptor antagonist Manning compound indicate that AVT regulates the expression of social behaviors in pupfish. Further studies will investigate whether changes in AVT physiology underlie the population variation seen among Death Valley pupfishes.