Meeting Abstract

P3.158  Sunday, Jan. 6  An investigation of the statocyst sensory system in Armina californica GILL, KP; RICE, JL*; MURRAY, JA; CAIN, SD; University of Mebourne; Eastern Oregon University; California State University, East Bay; Eastern Oregon University ricejl@eou.edu

Statocysts are a common type of gravireceptor within the invertebrate taxa. This system is analogous to the vertebrate auditory-vestibular system that utilizes the otolith. Within molluscan taxa, the statocyst is an epithelial sac filled with a fluid called statolymph. The epithelial wall is continuous with the statocyst receptor cells, each bearing several hundred sensory cilia and free-moving calcium carbonate stones or statoconia. Most information regarding the statocyst sensory system has been obtained from terrestrial snails such as Helix and Lymnaea. However, the statocyst sensry system has been described in only a few marine gastropod species. Most work into statocysts has involved opisthobranchs due to their large, re-identifiable neurons, as well as their symmetrical and relatively simple central nervous system (CNS) and stereotypic behaviors. In this study we investigated the statocyst sensory system in the nudibranch Armina californica. We used the righting response, initiated when the animal is rolled onto its back, to determine the role of the statocyst and the sensory neurons in this gravireceptor-initiated behavior. We used time-lapse video analysis to record and analyze the righting response. We used cell tracing techniques to determine the innervation pattern of the statocyst and investigated the neural response of pedal nerves to mechanical stimulation of both contralateral and ipsilateral statocysts by recording extracellularly from the pedal nerves innervating the foot. This study provides the initial steps in determining the neural pathways activated by the statocyst sensory system underlying righting behavior.