NEW YORK, April 8 (UPI) -- Fish in perpetual darkness in caves sleep less than surface counterparts, suggesting a genetic basis of sleep patterns and disorders, U.S. researchers say.
New York University biologists say the finding may shed light on how genetic makeup contributes to sleep variation and disruption in humans.
The researchers examined three cave fish populations in northeast Mexico. While surface and cave fish have different physical appearances and behaviors brought about by evolutionary change, the researchers sought to determine whether the sleep patterns of cave fish also changed as they adapted to cave life.
Researchers found that, over a 24-hour period, surface fish slept an average of more than 800 minutes while cave fish slept an average of 110 to 250 minutes.
To determine if genetics played a role in the varying sleep behaviors, researchers bred cave and surface fish and examined the sleep patterns of these hybrids, finding the hybrid fish nearly matched the sleep patterns of the cave fish, rather than those of the surface fish, demonstrating that cave fish carry a dominant gene for less sleep.
"In some ways, the sleep phenotypes of cave fish are similar to those of humans with sleep disorders," NYU biology Professor Richard Borowsky said. "They go to sleep, but only for relatively short periods, then they awaken and remain awake for relatively long periods.
"The next job is to identify the genes which are responsible for sleep modification in the cave fish," he said. "They would be good candidates for the genes responsible for insomnia and other sleep disorders in humans."
