Data from: Molecular circadian rhythms are robust in marine annelids lacking rhythmic behavior

The circadian clock controls behavior and metabolism in various organisms.
However, the exact timing and strength of rhythmic phenotypes can vary
significantly between individuals of the same species. This is highly
relevant for rhythmically complex marine environments where organismal
rhythmic diversity likely permits the occupation of different
microenvironments. When investigating circadian locomotor behavior of
Platynereis dumerilii, a model system for marine molecular chronobiology,
we found strain-specific, high variability between individual worms. The
individual patterns were maintained for several weeks. A diel head
transcriptome comparison of behaviorally rhythmic versus arrhythmic
wildtype worms showed that 24h cycling of core circadian clock transcripts
is identical between both behavioral phenotypes. While behaviorally
arrhythmic worms showed a similar total number of cycling transcripts
compared to their behaviorally rhythmic counterparts, the annotation
categories of their transcripts, however, differed substantially.
Consistent with their locomotor phenotype, behaviorally rhythmic worms
exhibit an enrichment of cycling transcripts related to
neuronal/behavioral processes. In contrast, behaviorally arrhythmic worms
showed significantly increased diel cycling for metabolism- and
physiology-related transcripts. The prominent role of the neuropeptide
pigment-dispersing factor (PDF) in Drosophila circadian behavior prompted
us to test for a possible functional involvement of Platynereis pdf.
Differing from its role in Drosophila, loss of pdf impacts overall
activity levels, but shows only indirect effects on rhythmicity. Our
results show that individuals arrhythmic in a given process can show
increased rhythmicity in others. Across the Platynereis population,
rhythmic phenotypes exist as a continuum, with no distinct ‘boundaries’
between rhythmicity and arrhythmicity. We suggest that such diel rhythm
breadth is an important biodiversity resource enabling the species to
quickly adapt to heterogeneous or changing marine environments. In times
of massive sequencing, our work also emphasizes the importance of time
series and functional tests.