A Snail’s Approach to Leech Reproduction

D. A. Wagenaar, T. Huang, W. B. Kristan, and K. A. French

36th Annual Meeting of the Society for Neuroscience, Atlanta, GA, 2006. Prog. no. 259.8

Leeches (Hirudo medicinalis) are simultaneous hermaphrodites, and although they have been successfully bred in captivity for many years, little is known about the neuronal control of their mating behaviors. We have found that conopressin, a vasopressin analog isolated from cone snail venom, elicits motor behavior that closely resembles mating. The behavior is produced in whole leeches, in semi-intact body walls, and in isolated nerve cord preparations. We have found that ganglia 5 and 6, located in the reproductive segments, are necessary and sufficient to control this behavior. These ganglia control waves of muscle contraction that spread to most of the rest of the body. Using suction electrode recordings and simple spike sorting, several distinct neurons have been found to play a role in the behavior. We have focused on cell DE-3, the excitor of dorsal longitudinal muscles. As in swimming and crawling, the timing of cell DE-3 activity is synchronized between the left and right side of each ganglion. However, the amplitude of the waves varies in cycles of 5-10 minutes, antisymmetrically between left and right sides, corresponding to the period of the longitudinal twisting observed in the intact animals, and likely causing it. Our current efforts focus on imaging ganglia 5 and 6 with voltage sensitive dyes, to study the unknown central pattern generator that we predict underlies the activity patterns of the motor neurons during mating.

[Back]