Circatidal control of gene expression in the deep-sea hot vent shrimp Rimicaris leurokolos

Biological clocks are a ubiquitous feature of all life, enabling the use of natural environmental cycles to track time. Although studies on circadian rhythms have contributed greatly to the knowledge of chronobiology, biological rhythms in dark biospheres such as the deep sea remain poorly understood. Lacking day-night cycles, the deep sea allows organisms to adapt to other temporal effects such as geophysical cycles, which remain unknown. Here, based on a laboratory free-running experiment, we reveal potentially endogenous rhythms in gene expression of the deep-sea hydrothermal vent shrimp Rimicaris leurokolos . Oscillations with ∼12-hour periods, likely reflecting tidal influence, greatly prevail over others in the temporal transcriptome. The tidal transcripts exhibit an antiphased expression pattern divided into two internally synchronized clusters, correlated with wide-ranging biological processes that occur in the nucleus and cytoplasm, respectively. Exhibiting robust tidal transcriptional expression but relatively weak rhythmicity in circadian clock genes, R. leurokolos likely depends on a circatidal clock consisting of at least some components independent of the circadian clocks. In addition, comparing the tidal transcripts with the ∼12-hour ultradian rhythms genes in fruit fly and mouse shows large similarity, indicating the likely scenario of broad impact of tide on the ∼12-hour oscillations across the metazoan. These findings not only provide new insights into the temporal adaptations in deep-sea organisms but also highlight deep-sea hydrothermal vent organisms as intriguing models for chronobiological, particularly 12-hour ultradian rhythms, studies. ### Competing Interest Statement The authors have declared no competing interest.