ANATOMY AND PHYSIOLOGY OF AN EXTRA-NASAL CHEMOSENSORY SYSTEM IN THE SEA LAMPREY

RATIONALE: In addition to the olfactory system, lampreys contain solitary chemosensory cells, termed oligovil-lous cells, located along the surface of the body, oral disc and gills (Whitear and Lane, 1983); as well as multicellular taste buds on the pharynx and gill arches (Barreiro-Iglesias et al., 2010). In 1985, Baatrup and Døving found that chemical stimuli for oligovillous cells in brook lamprey, included trout conditioned water. In teleosts, solitary che-mosensory cell activity is associated with foraging, feeding, and reactions pertaining to food palatability and predator detection (Finger, 1997). Despite the important links between chemoreception and motor behavior in various species, little is known regarding this interesting extra-nasal chemosensory system in lampreys. We propose to examine the neuroanatomy and neurophysiology of this system in the sea lamprey and to determine how closely it is linked to movement. Our general hypothesis is that the solitary extra-nasal chemosensory system of the sea lamprey has an important role in generating motor responses to chemicals in the environment of the animal. In particular, this system may respond to feeding stimuli by helping to discern the palatability of potential food. We postulate that solitary chemoreceptor cells in the lamprey respond to non-aversive and aversive chemical stimuli.

OBJECTIVES: The specific aims of this study will be to: 1) Define the distribution of the extra-nasal chemosensory cells. 2) Identify the chemical stimuli that activate these cells, including water from tanks holding prey salmonids, simple molecules associated with feeding in teleosts, the bitter compound denatonium, and human saliva - known from anecdotal evidence to stimulate a dramatic aversion response. 3) Define the neuroanatomical pathways associ-ated with the extra-nasal chemosensory cells. 4) Define the physiological inputs from the chemosensory cells to brain regions controlling locomotion and determine whether extra-nasal sensory inputs induce swimming behavior.
It will be highly beneficial for sea lamprey management if multiple chemosensory systems (olfactory and extra-nasal) are engaged to control locomotor behavior during trapping and population assessment. Once feeding and foraging stimuli, as well as the ensuing motor responses are understood; the luring of transformed lampreys could be developed as a control measure or as a tool for population assessment. Stimulating extra-nasal chemosensory activity may also help out with directing movement during trapping mature life stages. Additionally, the use of selective aversive ago-nists could maximize lamprey deterrence while minimizing irritation to other animals.