Molecular neurogenetics of rhythmicity in intertidal crustaceans

Eurydice picture2The major environmental variable affecting interdidal organisms is the daily ebb and flow of the tides. Accordingly, in all examples so far studied, anticipation of immersion, via a so called endogenous, free-running, “circatidal clock” with a period of ca. 12.4h seems to be universal. In contrast, it has been long known that terrestrial organisms possess biological clocks which free-run with an approximate 24h rhythm. The molecular components that make up the circadian clock have been widely conserved in friutflies (Drosophila), rodents and other mammals, and the interacting feedback and feedforward loops involved in maintenance of the circadian oscillators (the clock) are well known. In contrast, we know very little about the molecular mechanisms involved in the circatidal clock- Is it just a circadian clock(s) running at twice the speed? Or are there new components; indeed is there a novel circatidal clock, which must, in evolutionary terms pre-date that of the terrestrial circadian counterpart?
We are examining this problem by using a model crustacean which possesses extraordinarily robust circatidal rhythms, the speckled sea louse, Eurydice pulchra. This animal is useful since its circatidal rhytms can be salvaged in arrhythmic animals, by cycles of turbulence (shaking) at 12 h intervals. Our experimental approach using gene knockdown (dsRNAi), pharmacological intervention and environmental/behavioural manipulation has revealed that separate (yet interacting) clock systems reside in Eurydice; one that orchestrates 12.4h swimming rhythms and a distinct 24h oscillatory system that drives daily modulation of swimming activity and rhythms of chromatophore dispersion (Zhang et al, 2013). Our work is now focussed on sequencing the Eurydice genome and interrogating global gene expression patterns using Illumina RNAseq strategies to identify candidate ‘tidal’ genes.

This project is coordinated by Professor C.P. Kyriacou (Leicester), and involves the invaluable input of Dr. M.H. Hastings, who first described the rhythmic behaviour of Eurydice in detail over 20 years ago!

Funded by BBSRC
Researchers: Prof. C.P. Kyriacou, Dr L. Zhang, Dr Matt Blades (Leicester), Dr. D.C. Wilcockson (Aberystwyth), Dr, S.G. Webster (Bangor), Dr. M.H. Hastings (LMB: Cambridge)