RABURN, B.L.*; MOORE, P.A.; Bowling Green State Univ.: Serotonin and Agonistic Interactions in O. rusticus
Agonistic interactions between crayfish establish a social role of dominance between the pair of combatants. These interactions are highly ritualized and can be described by a series of common behaviors of increasing or decreasing levels of aggression. The level of aggression in crayfish can be influenced by many different factors, which include physical size, ownership of resources, previous social history and neurochemistry. Aggressive behavior in the crayfish O. rusticus is thought to be modulated and regulated by the neurotransmitter serotonin (5-HT). To provide a neural mechanism tying serotonin to aggression in O. rusticus, injections of appropriate amounts of serotonin agonists, serotonin antagonist, and serotonin-specific neurotoxins were performed, and measures of subsequent social behavior and aggression were obtained. Crayfish were immobilized and injected with either saline control or one of three drugs in saline. The tested drugs were an agonist, 1-(3-chlorophenyl)piperazine (m-CPP) and an antagonist, cinanserin both at 3 x 10-3 M, and a neurotoxin, 5,7-dihydroxytryptamine creatinine sulfate at 5 x 10-4 M. Animals were placed in a fight arena and allowed to recover, then fought against size matched na�ve individuals that were injected with saline. We performed blind analysis of video tapes for the following behavioral measures: winner, loser, initiator, and time to different intensities. Results from these studies showed a significant trend in increased aggression of animals injected with the agonist, but no declines in aggression with the antagonist. However, even though aggression was increased in animals injected with m-CPP, the agonist did not lead to an elevated social status or dominance, as determined by winners. Our data clearly shows that the internal aggressive states of the crayfish are altered through drug therapies, and introduces a possible disconnect in the relationship between aggression and dominance in crayfish.
