By Jim Fessenden
At a glance:
Scientists at UMass Chan Medical School and the Marine Biological Laboratory at Woods Hole have shown that the four core clock genes responsible for maintaining circadian rhythms in animals— Per, Cry2, Bmal1 and Clk —also regulate circatidal behavior in the crustacean Parhyale hawaiensis . Their transcriptional wiring—how these genes interact with each other—however, differs, allowing these tiny shrimp-like creatures to maintain an internal 24-hour clock synchronized with light and dark cycles and a 12.4 hour clock synchronized with the tides.
Published in Current Biology , these findings suggest that the genetic system controlling circadian and circatidal rhythms is highly malleable. Better understanding of this system may help scientists potentially develop novel interventions for diseases linked to circadian system disruption such as jet lag and shift work, as well as better understand addiction biology, metabolism and obesity.
“The genes building these clocks seem to be quite plastic because they can generate rhythms of 12.4 hours to 24 hours, adjusting their mechanism to allow different periodicities,” said Patrick Emery, PhD, professor of neurobiology at UMass Chan. “This plasticity is interesting, as it informs our understanding of biological clock mechanisms, and could help us, at some point, adjust our circadian system if we need to for one reason or the other.”
What are circadian and circatidal clocks?
The circadian clock is a biological mechanism that generates and maintains 24‑hour rhythms in living organisms. It allows animals to anticipate and adapt to the day/night cycle. Monarch butterflies and migratory birds use the circadian clock during sun-compass navigation. This timekeeper helps them maintain a southern or northern flight path even though the sun moves from east to west during the day. The circadian clock also signals when to initiate migration in the spring or fall. In humans, this clock helps maintain sleep/wake cycles and influences biological processes such as metabolism and hormone release.
Like most animals, the tiny shrimp-like crustacean P. hawaiensis has an internal circadian clock set to the rhythm of 24-hour days and synchronized with light and dark cycles. Additionally, however, it maintains a 12.4-hour clock to help it time its behavior with the 12.4-hour cycle of tides.
How do circadian neurons and circatidal neurons differ?
In their most recent collaboration, the pair have identified three more core clock genes — Cry2 , Per , and Clk — that are necessary for maintaining both the circadian and circatidal clocks in P. hawaiensis . Each of these genes is expressed in the specific neurons that make up the two internal clocks, and these clock neurons regulate the metabolism and behavior of P. hawaiensis by keeping time from environmental cues.
Victoria Louis, PhD, a postdoctoral researcher in Emery’s lab, found that while the genes controlling circatidal and circadian rhythms are the same, how they are transcriptionally wired in individual neurons is different. Specifically, she found that in circatidal neurons CLK represses expression of Per independently of BMAL1, a deviation from its normal role in circadian neurons. This suggests that there are different transcription factors that control Per expression in circatidal neurons than circadian neurons.
Going forward, investigators plan to explore precisely how these shared genes interact with each other to produce a 12.4-hour rhythm in one set of neurons and a 24-hour rhythm in others, and which transcription factors are involved.
Current Biology
Experimental study
Animals
Core circadian clock genes control molecular and behavioral circatidal rhythms in Parhyale hawaiensis
2-Sep-2026