Meeting Abstract
The nudibranch, Melibe leonina, expresses a circadian rhythm of locomotion, and we recently determined the sequence of multiple circadian clock transcripts that may play a role in controlling these daily patterns of behavior. In this study, we used this information to help us: 1) identify putative clock neurons using fluorescent in situ hybridization (FISH); and 2) determine if there is daily expression of clock transcripts in the Melibe brain using quantitative PCR. FISH indicated the localization of the clock-related transcripts clock, period, and photoreceptive and non-photoreceptive cryptochrome (p- and np-cry) in two bilateral neurons in each cerebropleural ganglion and a group of >6 neurons in the anterolateral region of each pedal ganglion. Double-label experiments confirmed colocalization of all four clock transcripts with each other. Quantitative PCR demonstrated that period, p-cry and np-cry exhibited a significant difference in expression levels over 24 hours, while differential expression of clock transcripts was just under the significance threshold. These data suggest that the putative circadian clock in Melibe consists of a small number of identifiable neurons that express circadian genes with a daily rhythm.
