Sören Häfker, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven
Hidden personalities: individual-specific and multi-level circadian rhythms in the worm Platynereis
Circadian clocks control daily behavior and metabolic processes in countless organisms. However, rhythmic patterns can strongly differ between individuals within a species. Additionally, rhythmicity occurs on several organismic levels that do not always match each other. The annelid worm Platynereis dumerilii inhabits shallow coastal waters around Europe and shows well-defined diel/circadian rhythms of locomotor activity. However, even siblings worms show a variety of different behavioral patterns that are consistent over time and often show little resemblance with “mean” patterns. To explore the molecular basis of these rhythmic “personalities”, diel transcriptomes were generated from the heads of worms with highly rhythmic vs. arrhythmic behavior. Surprisingly, worm behavioral rhythms strongly contrasted with the circadian clock and rhythms of metabolic transcripts, illustrating the importance of differentiating not just between individuals, but also between levels of biological organization. The results highlight the fact that variability is not “background noise”, but an inherent feature of biological systems, with relevance reaching from population resilience in changing environments to individually-tailored patient treatment in chronomedicine.
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