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Both tidal and circadian clocks guide the behavior of some animals

In order to maximize its feeding time, the nocturnal isopod must set out for food when nighttime and low tide are synchronized.

By Brooks Hays
Both tidal and circadian clocks guide the behavior of some animals
The nocturnal sand-burrowing isopod, Scyphax ornatus, uses its circadian and tidal clocks to feed when night and low tide coincide most completely. Photo Courtesy University of Auckland

June 20 (UPI) -- New research has revealed how circadian and tidal clocks interact to govern the behavior of some animals -- like the crustacean species Scyphax ornatus, a sand-burrowing isopod native to the beaches of Australia.

The circadian clock is well studied. Scientists have identified genes and the portion of the brain linked with our innate understanding of the temporal rhythms of days and nights.

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But there are other internal clocks. For some animals, lunar and tidal cycles are equally as important as day-night patterns. These clocks have remained poorly understood, however.

By observing the feeding patterns of Scyphax ornatus, a team of researchers at the University of Auckland were able to get a better sense for how an animal's tidal clock functions.

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Scyphax ornatus feeds on plant and animal debris deposited on the beach by the waves and ocean tides. Low-tide is the ideal feeding time for the species. In order to maximize its feeding time, the nocturnal isopod must set out for food when nighttime and low tide are synchronized.

Researchers transplanted several specimens from Auckland's Piha beach to the laboratory, where scientists could manipulate light and tidal patterns.

Their analysis -- detailed in the journal Scientific Reports -- showed the isopods alter their behavior to follow changing day-night and tidal schedules. The creatures can also continue to follow the rhythms of their internalized circadian and tidal clocks even when denied external stimuli.

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"What we have found is that, in the laboratory, with light and tide cycles artificially manipulated, these animals follow the same rules of behavior as they would in the wild," researcher James Cheeseman, a health scientist at the University of Auckland, said in a news release. "So we can very accurately change the semilunar rhythm by changing the perceived length of the day and tidal cycles."

"That tells us their semilunar or fortnightly behavior continues to be regulated by the interaction of circatidal and circadian clocks even where there is either no external stimuli or they are in an environment with artificial light cycles or tidal cycles," Cheeseman concluded.

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