Arctic reindeer, which live most of the year in 24-hour darkness or daylight, may lack an internal clock common to most organisms, according to research published online today (March 11) in __Current Biology.__
Image: Per Harald Olsen/Wikimedia
The study found no evidence of cyclic changes in reindeer gene expression, consistent with behavioral evidence that the arctic animals do not rely on such daily rhythms. But the fact that the researchers only investigated two clock genes in one cell type is not conclusive evidence that reindeer completely lack a circadian clock, said linkurl:Michael Menaker; from the University of Virginia, who was not involved in the study. "If it were shown that there was no circadian organization anywhere -- that would be very surprising," he said. Most organisms are thought to have a strong circadian clock, observable in behavioral patterns and the cyclic expression of clock genes, which scientists believe confer...

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