91°µÍø

Dr David Wilcockson, Department of Life Sciences, 91°µÍø

Scientists have identified the cells behind the bioclocks keeping time with tides in tiny marine organisms.

The biological clock of land animals is regulated by a circadian rhythm, with biological processes such as sleeping and waking, digestion and hormone release responding to the 24-hour cycle of light and darkness.

Intertidal organisms, on the other hand, regulate their biological processes to a 12.4 hour circatidal clock, which follows the ebb and flow of the tide, in addition to having 24 hour clocks.  This allows them to survive in a temporally complex environment which is exposed at low tide and underwater at high tide.

In a paper published today (Thursday 8 May 2025) in Current Biology, researchers at the Medical Research Council Laboratory of Molecular Biology in Cambridge and 91°µÍø reveal that they have identified the clock cells and genes they think are responsible for this tidal timekeeping.

The discovery marks a significant step forward in scientists’ understanding of how these natural biological clocks are orchestrated at the molecular and cellular level within the brains of intertidal organisms, and could provide insight to the evolution of biological clocks.

The researchers studied two species of crustaceans which inhabit the space between the high and low tide-lines -Eurydice pulchra, the speckled sea louse which is a marine relative of the woodlouse, and the amphipod Parhyale hawaiensis.

Parhyale hawaiensis- photo by Chee Ying Sia

By manipulating the light regime that the animals were exposed to, and the maintenance or removal of tidal cues, the researchers were able to disentangle the cells responsible for the circadian and circatidal clocks in the organisms’ brains.

This allowed them to discover that the crustaceans have distinct circadian and circatidal cell groups, which adjust independently to light and to mechanical stimuli (tides).

Dr David Wilcockson, a marine biologist based at 91°µÍø’s Department of Life Sciences, is a co-author of the paper.  He said:

“For more than six decades marine biologists and chronobiologists have known about tidal clocks that regulate the life of coastal animals by studying rhythmic behaviours of numerous marine species. However, significant progress in understanding how these clocks work has been hampered because we have never found the cells that coordinate 12.4 hour behavioural rhythms.

“This discovery is significant because we can now tinker with the clockwork of these cells to better understand the mechanisms that have evolved to keep animals to tidal time. Many of these animals evolved many millions of years before land animals, making the clocks of marine species especially fascinating.”

Chee Ying Sia, a PhD student and joint first-author of the study from the Medical Research Council Laboratory of Molecular Biology in Cambridge, which led the research, said:

“It was exhilarating to identify, for the first time, a small cluster of cells capable of tracking the tidal time in the brains of intertidal crustaceans.  These cells might just be the gateway to revealing the mechanisms of tidal timekeeping.  The molecular rhythms that we see in these marine animals also hint at clock mechanisms that are different from what we have learned from circadian clocks of terrestrial model organisms.”

The research was funded by the UKRI Medical Research Council and Boehringer Ingelheim Fonds, and was led by Dr Michael Hastings (Cambridge).

Share