Meeting Abstract
P3.13 Monday, Jan. 6 15:30 Keeping Your Enemies Close: Neural and Hormonal Mechanisms of Cooperative Defense in a Cichlid Fish WEITEKAMP, C. A. *; HOFMANN, H. A.; UT Austin; UT Austin chelseaweitekamp@gmail.com
Neighboring territorial males of many species exhibit less aggression toward each other than toward strangers (“dear enemy effect”). To maintain this relationship and avoid the costs of renegotiating boundaries with a new neighbor, a territorial male may actively display aggression toward a male intruding on the neighboring territory. While such defensive coalitions are thought to be widespread in nature, they have rarely been observed nor are the underlying neuroendocrine mechanisms known. Using the African cichlid fish Astatotilapia burtoni, we first show that upon repeated exposure to a territorial neighbor, levels of aggression, androgens, and cortisol quickly decrease over time. We then demonstrate that the presence of a novel intruder in one of two adjacent territories results in joint territorial defense in a manner that depends on the size and behavior of the resident partners and thus implies cognitive processes. To gain functional insight into this behavior, we manipulated the dopamine D2 receptor system in the resident male. Treatment with a D2 agonist causes aggression to be directed toward the neighbor, while blocking D2 signaling directs more aggression toward the intruder. Using immunohistochemical detection of the immediate-early gene c-Fos, we identified neural activity in nodes of the Social Decision-Making network. For example, neural activity in a subregion of Dm (putative basolateral amygdala homolog) and the parvocellular preoptic area correlates with both intruder size and aggression. To further investigate the neural correlates of these behaviors, we are co-localizing c-Fos with the dopamine system. Our results provide the first evidence of defensive coalitions in a vertebrate, and provide novel insights into the neuroendocrine basis of cooperative behavior and social cognition in general.
