They were also able to block the circadian cycle by exposing Eurydice to a constant bright light for many days.
With both of these genetical and environmental manipulations, the circadian rhythm in the sunscreen cells became severely disrupted, but the tidal swimming rhythm just kept on ticking every 12.4 hours.
This showed conclusively that the animals' tidal patterns are independent of their 24 hour circadian clock.
The researchers believe these results along with a parallel study on coastal worms published simultaneously in the journal Cell Reports on 26 September which came to a similar conclusion - suggest that many other coastal animals will have similar circatidal systems.
Principal investigator Professor Charalambos Kyriacou, Professor of Behavioural Genetics in the University's Department of Genetics, said: "Most coastal animals will have 24 hour rhythms in some aspects of their physiology, but their most important geophysical cycle is the tides coming in and out and so they have evolved circatidal rhythms to cope with this rapidly changing environment.
"Eurydice pulchra have both a 24 hour rhythm and a 12.4 hour rhythm, which relates to the gravitational pull of the moon on the earth's tides.
"People have speculated that the 24 hour clock could be driving the 12.4 hour clock, because all it would take is for two 24 hour clocks in the brain to work in antiphase with each other.
"This would give two approximate 12 hour rhythms. We have shown that if we knock down the genes that code for their 24 hour clock, the animal still has very robust tidal rhythms.
"This shows that the 12.4 hour clock is independent from the circadian clock. I expect tidal rhythms in many coastal organisms will follow this rule including insects, crabs, even plants."
|Contact: Charalambos Kyriacou|
University of Leicester