P2.123 Thursday, Jan. 5 In search of biological clock neurons in the central nervous system of the nudibranch Melibe leonina BOUCHARD, J.B.; MITCHELL, R.; CAMPBELL, A.; KIROUAC, L.E.; LACHANCE, S.; NAIMIE, A.A.; WATSON, III, W.H.; NEWCOMB, J.M.*; New England College; University of New Hampshire; University of New Hampshire; New England College; University of New Hampshire; New England College; University of New Hampshire; New England College firstname.lastname@example.org
Daily rhythms of activity are controlled by neural networks that function as endogenous biological clocks. The molecular time-keeping mechanisms involve the rhythmic expression of various proteins, such as clock and timeless. In addition, pigment dispersing hormone (PDH) is believed to be a putative output signal from the clock in certain invertebrates. The goal of this project was to determine the location of the circadian clock in the marine gastropod Melibe leonina by treating brains with antibodies to clock, timeless, and PDH. Two large clock-immunoreactive neurons were consistently present in the left pleural ganglion, with a small number of other neurons labeled in a subset of the brains examined. The location and number of clock-immunoreactive neurons was not significantly different between animals sacrificed at different times during a twenty-four period. Timeless-immunoreactive neurons were present near the eyes in the middle of each cerebropleural ganglion. PDH-immunoreactive nerve tracts were present in the anterior cerebral ganglia and smaller tracts spanned the pedal connectives. PDH-immunoreactive axons and cell bodies were also visible in the buccal ganglia and throughout the esophagus and associated ganglia, suggesting PDH may play a role in feeding. Additional genome sequencing and custom species-specific antibody construction will facilitate continuing studies investigating the location of the circadian clock in M. leonina. In conjunction with planned pharmacological and electrophysiological studies, these results will eventually be used to establish M. leonina as a model system to investigate the neuroethology of circadian rhythms.