September 26, 2013
Internal Clock Helps Marine Animals Follow The Tides
Lee Rannals for redOrbit.com - Your Universe Online
Marine animals have an internal clock to help them keep up with their schedules, according to findings published in the journals Current Biology and Cell Reports. The new findings suggest that these animals may be using these clocks as standard operating equipment.
"The discovery of the circadian clock mechanisms in various terrestrial species from fungi to humans was a major breakthrough for biology," says Charalambos Kyriacou of the University of Leicester, who led one of the two studies on an inter-tidal crustacean known as a speckled sea louse. "The identification of the tidal clock as a largely separate mechanism now presents us with an exciting new perspective on how coastal organisms define biological time."
The second study focused on interactions between the familiar 24-hour circadian clock and a circalunar clock in a marine bristle worm. They found that this worm possesses an independent, endogenous monthly and daily body clock.
"Taking this together with previous and other recent reports, evidence accumulates that such a multiple-clock situation might be the rule rather than the exception in the animal kingdom," stated Kristin Tessmar-Raible from the Max F. Perutz Laboratories at the University of Vienna.
Kyriacou and colleagues used environmental and molecular manipulations of the daily clock to show that when the 24-hour circadian clock is disrupted in a sea louse, the 12.4-hour tidal clock helps to keep the animal's internal clock. Kyriacou said they were surprised to discover how hard-wired and independent the tidal clocks in these animals were.
"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," the researcher said in a statement. "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," said Kyriacou.
Tessmar-Raible's team showed that bristle worms' lunar clock continued to function even when the researchers disrupted the animals' circadian clock. They also saw how the two clock mechanisms interact, finding that the length and strength of the circadian rhythm adjusts according to the circalunar clock.
"This means that there might be a whole level of regulation on the molecular and behavioral level for which we have just scratched the surface," Tessmar-Raible says.
These new discoveries raise new questions about the molecular and cellular natures of these clocks, as well as the role they play in animal behavior.