compete with other inputs for the control of the LGI. Learning Repeated tapping of the abdomen leads to habituation of the tail flip mechanism. However, self–habituation is prevented by command neuron–derived inhibition because when a tail flip is begun, the mechanisms that induce habituation are repressed. The habituation occurs at the level of the A type and C type interneurons, which experience synaptic depression. The habituation process is also mediated further up the circuit through the buildup of tonic inhibition, brought on by the repeated stimulation. Social status The feedback from social situations affect a crayfish's ability to perform a tail flip. Serotonin levels are affected by social status. High levels are associated with aggressive behavior and a reduction in the frequency of tail flips performed. This is because the excitability of the LGI is decreased. Aggressive dominant males have a moderate reduction in tail flips while the subordinates have a much lower occurrence of tail flips. This presents a paradox since this means that subordinates are more likely to get killed. However, it was found that subordinates are more likely to use non-giant-mediated escape, indicating that the reduction in tail flips and enhancement of non giant escape is adaptive. Changes in social status should correlate with changes in serotonin levels, resulting in changes in the escape strategies used by the crayfish. However this is only true when submissive crayfish become dominant, and not the reverse. The neuromodulatory processes of facilitation and inhibition seem to be mediated by different cell receptors. Differences in the effects of serotonin on the behavior of the crayfish seem to be the result of differences in the populations of these receptors. It is unknown how these modulation processes convey the information to the LG, and how the behavioral changes are precipitated. Evolution of the tail flip escape mechanism It has been hypothesized that the tail flip is derived from an ancient limb protraction driven (as opposed to tail flexion-driven) mechanism. This is because the SGs appear to be modified limb motor neurons whose peripheral axons affect the legs and swimmerets, but end blindly without any known function. It is known that another effect of Giant Fiber excitation is limb promotion which suggests that the premotor limb interneurons may be ancestors of the Giant Fibers. It has been speculated that the ancestral escape mechanism was most likely a backwards jump due to the simultaneous protraction of