HARA, E; HEWS, D. K.: Brain sex dimorphism of the eastern fence lizard, Sceloporus undulatus, a species with male aggression.

The sexes differ in a variety of behaviors, and in many animals sexual dimorphism in brain nuclear volumes are thought to contribute to such differences. We are studying the neuroendocrine basis of sex and species differences in territorial aggression in Sceloporus lizards. We present an analysis of brain sexual dimorphism in S. undulatus, a species in which males exibit high levels of aggression associated with territoriality but females do not. Nissl-stained histological sections of the brain were analyzed for sexual dimorphism (N = 6 of each sex). We evaluated a number of brain regions thought to mediate male aggression including the anterior hypothalamus and preoptic area, lateral hypothalamus, lateral septum, amygdala, and the medial accumbens. We measured volumes of these regions and compared those for males and females, contolling for body size differences. These results will be compared to an earlier immunocytochemical study describing brain androgen receptor locations in males and females of this species.