2008 Eighth Annual Beckman Scholars Symposium
Saturday Poster Session - July 29, 2006

Heather Heinz
Department of Zoology
North Carolina State University		 Territorial Aggression in Bluehead Wrasse Social Hierarchies
  Field research is inherently expensive and often limited to certain seasons of the year. By understanding the degree of fidelity to wild behaviors in the laboratory, scientists may better understand the utility of laboratory simulations of wild social structures. In the wild, the coral reef fish Thalassoma bifasciatum displays complex, clearly defined social dominance hierarchies based on sex and size. We conducted laboratory studies aimed at testing the effects of different neural signaling systems on aggressive behavior and comparing interactions in the laboratory setting to those in the wild. Neurochemical manipulations predicted to alter typical aggressive behavioral responses to social stimuli did not produce consistent and statististically significant changes in behavior. Treatments included manipulating nitric oxide production via injection of inhibitors and substrates and dopamine signaling via a receptor agonist and antagonist. To compare social interactions in laboratory and wild settings, we constructed social groups of 4-5 same-sex fish along a size gradient. While the largest fish were dominant to smaller fish, we did not find statistically significant differences in aggressive behavior between the largest and second largest fish. Further, aggressive behaviors by the second largest fish did not significantly increase when the largest fish was removed. However, aggressive behaviors "received" by this newly-dominant fish showed a decreasing trend as these fish became dominant, consistent with Shapiro's model of "received behavior" as a strong cue in regulating sex change. Newly dominant fish also spent more time under cover. There was some evidence that the diel cycle of behavior seen in nature is maintained. Time of day affected chase frequency and this varied significantly by sex. No courtship behavior was observed. Small sample sizes may have influenced results and these will be increased. Field studies will be conducted for comparison during May-June at the Glover's Reef Marine Research Station in Belize.