HERBERHOLZ, J.; ISSA, F.A.; EDWARDS, D.H.: The Role of Tailflip Behavior in Crayfish During Dominance Hierarchy Formation.

When placed together in a limited space, crayfish engage in agonistic interactions that lead to formation of social dominance hierarchies. The interactions feature attacks, where one animal physically assaults another with its claws, approaches, where no contact occurs, retreats, where one animal walks away from another, and escapes, where rapid tail flexions and extensions thrust the animal away from the opponent. Escapes are triggered by activation of three discrete neural circuits in crayfish, two of which depend on giant command neurons. To determine how these different escape circuits were used during dominance hierarchy formation, we placed a pair of electrodes in the aquarium with the animals to record electric field potentials produced by the giant neurons, the motor neurons and the muscle. Activation of each tailflip circuit could be determined from differences in the field potentials that they produce. We used this non-interfering method to record activation of the circuits in pairs of previously unacquainted animals placed together in a freshwater aquarium. We found that during initial fighting, both animals performed attacks, approaches, and a new agonistic behavior, offensive tailflips. This behavior is performed by one animal as it grapples another; the offensive tailflips thrust the animal above its opponent which is dragged about. Quite suddenly, usually after a bout of offensive tailflipping by one animal, the other will initiate a series of escape tailflips mediated either by the medial giant neurons or by the non-giant neurons. This is the decision point for social hierarchy formation, after which the behavior of the dominant and subordinate animals diverge.