Meeting Abstract
Brains are composed of fundamentally similar cells, making it possible for conclusions derived from simple brains to be applied to more complex systems. The sea slug T. tetraquetra is ideal for understanding the neural pathway through which olfactory sensory information is transduced into a motor response because its brain contains few cells which are large and easily identified. The goal of this research is to describe the chemotactic neural pathway, beginning with odorant contact with the rhinophores and ending with a motor response in the form of a change in direction of motion. Tritonia use rhinophores to sense odors and have been shown to respond to prey, predator, and conspecific odors with appropriate turning behavior (Wyeth and Willows 2006, Wyeth et al. 2006). Olfactory information is sent to the brain via Lateral Cerebral Nerve 1 (LCN1), while changes in direction of motion are mediated by Pedal Neuron 3 (Pd3) (Redondo and Murray 2005). We initially hypothesized that LCN1 comes into direct contact with turn-inducing neurites of Pd3. Preliminary results show that fluorescent dyes introduced into LCN1 and Pd3 do not co-localize when imaged under confocal microscopy. Backfills done on LCN1 show cell body clusters in the pleural (Pl) and cerebral (Ce) ganglia with occasional cell bodies in the pedal (Pd) ganglion. Dye injections of Pd3 show the axon exiting the Pd ganglion via Pd nerve 3, and dendritic extensions in the pedal neuropil. Our research shows that the sensory transduction circuit for chemotaxis may be more complex than initially thought, with interneurons likely being part of the pathway. Another possibility is that since the association of Pd3 with turning behavior was determined through rheotaxis experiments rather than chemotaxis, Pd3 may not be involved in chemotactic turning.
