Molecular circadian rhythms are robust in marine annelids lacking rhythmic behavior

Area of Science:

• Marine Molecular Chronobiology
• Circadian Rhythms
• Behavioral Ecology

Background:

• Circadian clocks regulate behavior and metabolism, but individual rhythmicity varies within species.
• Rhythmic diversity in marine environments may allow adaptation to different microhabitats.
• Platynereis dumerilii is a model organism for marine circadian studies.

Purpose of the Study:

• To investigate the variability of circadian locomotor behavior in Platynereis dumerilii.
• To compare the transcriptomic profiles of behaviorally rhythmic and arrhythmic worms.
• To explore the role of pigment-dispersing factor (PDF) in Platynereis rhythmicity.

Main Methods:

• Observation of circadian locomotor behavior in Platynereis dumerilii strains.
• Diel head transcriptome analysis comparing rhythmic and arrhythmic wild-type worms.
• Functional analysis of the pigment-dispersing factor (PDF) pathway.

Main Results:

• High, strain-specific variability in individual circadian locomotor behavior was observed.
• Behaviorally arrhythmic worms showed distinct diel transcriptomic cycling patterns, enriched in metabolism and physiology genes, compared to rhythmic worms (enriched in neuronal/behavioral genes).
• Loss of PDF affected overall activity but had indirect effects on rhythmicity, unlike in Drosophila.

Conclusions:

• Individual rhythmicity is a continuum, with arrhythmicity in one process potentially linked to increased rhythmicity in others.
• Diel rhythm breadth in Platynereis serves as a biodiversity resource for adapting to changing marine environments.
• Emphasizes the importance of time-series and functional studies alongside large-scale sequencing.