Meeting Abstract

P2.82  Jan. 5  KINEMATICS AND NEURAL CONTROL OF GONOPODIAL THRUSTS IN Gambusia affinis affinis (BAIRD AND GIRARD, 1853) ROSA-MOLINAR, Eduardo*; GONZALEZ-CORDERO, Leria; ANDERSON, Curt; Univ. Puerto Rico-Rio Piedras; Idaho State University ed@hpcf.upr.edu

The Gambusia affinis affinis gonopodium serves to transfer spermatozeugmata into the female urogenital sinus. Gonopodial thrust is achieved by the action of a series of enlarged and specialized internal and superficial muscles that move the gonopodium from a resting position close to the body to a pre-copulatory position and finally to an erect position. Kinematic analysis of the thrust shows the gonopodium sweeps through an arc of nearly 180 degrees, from a completely angled posterovental position (or just slightly down and away in some films) to an anterior position that angles up about 10 degrees relative to the horizontal axis of the body. Even during body�s turn prior to the thrust, the gonopodium is maintained parallel to the body axis. As the gonopodium begins to sweep laterally and forward, the gonopodium moves through an angle directed about 15 degrees below a perpendicular axis (0 degrees). Males orient themselves just under females and to the side, but the distance is extremely variable, as the female is moving. The mean speed of the gonopodium thrust is 158 ms. To examine the neural controls of the thrusts, red-fluorescent 3,000 MW dextran Texas Red� was implanted into the musculature of the gonopodium. Analysis revealed the 3-D morphology of small multipolar motor neurons (means range from 7.7 to 11.9 μm) distributed in spinal cord segments associated with trunk vertebrae 8-16 (Tk8-16). The cell bodies and dendritic fields of these multipolar motor neurons overlap and are extensive. We also describe the 3-D morphology of commissural neurons axons that ascend, descend, and bifurcate throughout Tk8-16. This work was supported in part by NIH/NS390405-06.