Meeting Abstract

P1.97  Monday, Jan. 4  The activity of a magnetically responsive ciliary motor neuron during crawling in normal and reversed magnetic fields in the nudibranch Tritonia diomedea KATO, DF*; HUYNH, M; MINTER, JL; SINGH, G; MURRAY, JA; California State University, East Bay darcy.kato@gmail.com

The nudibranch mollusk Tritonia diomedea has an easily accessible nervous system with large neurons that can be identified across individuals. The largest pair of identified neurons are the Pedal 5 (Pd5) neurons located on the dorsal surface of the pedal ganglia. The cells are ciliary motor neurons that respond to changes in magnetic field orientation. It has previously been shown that activity in Pd5 increases both in response to magnetic field rotations and that the increase is correlated with an increase in the crawling rate of the animal. This study was designed to understand the role of the Pd5 cells in a freely crawling animal. Simultaneous extracellular recordings from the Pd5 cells during a semi-intact preparation were compared with crawling behavior in the slug in both an ambient magnetic field and a rotated magnetic field of similar strength. Turning and crawling behavior during recording were compared with behavior of the intact animal crawling in both an ambient and rotated magnetic field. In a normal magnetic field, change in angular velocity preceded an increase in activity of the right Pd5 cell with a cross correlation coefficient of 0.1 which peaked at 66 seconds. The cross correlation coefficient for the left Pd5 cell peaked at .04, with turning preceding cellular activity by 87 seconds. In a rotated magnetic field similar results were seen, and no preference for a certain magnetic heading was found. We conclude that Pd5 may not be involved in turning behavior as previously thought. These cells may be responsible for an increase in crawling speed in response to changes in the magnetic field and therefore may still be important in orientation and navigation.