08 September 2005

Fluorescent animals surprise Gulf of Mexico divers

Fluorescent shrimp, crabs that detect ultraviolet light in the sunless depths, and an unseen creature that tumbled a massive camera have surprised scientists diving in the Gulf of Mexico.

Their expedition has turned up an array of creatures that use fluorescence in ways previously unknown to science, the team, a collaboration of federally funded researchers, said on Friday.

The discoveries suggest that even animals living with no light from the sun can detect and use light, perhaps for hunting, mating and other purposes, the researchers report on their Internet Web site, http://oceanexplorer.noaa.gov.

"This is incredible because these animals are found down at 1,800 feet," said chief scientist Tammy Frank.

"As far as we know there is no ultraviolet light down there," Frank added in a telephone interview from aboard the team's ship in the Gulf of Mexico.

"If they are ultraviolet-sensitive the question is what the heck are they doing with it?" said Edith Widder of the Harbor Branch Oceanographic Institution in Ft. Pierce, Florida and the private Ocean Research and Conservation Association.

"We are barely scratching -- I was going to say the surface but the bottom would be more appropriate."

The National Oceanic and Atmospheric Administration funded the expedition to sites around the Gulf of Mexico. The researchers had to divert to Galveston, Texas to avoid Hurricane Katrina last week, but left an undersea camera to record the undersea activity.

Frank said she designed a special red-light camera that would not frighten away or blind the extremely light-sensitive creatures that live so far from the light.

"We are exploring the deep sea with new eyes," Frank said.

"Traditionally, most of seep sea operations use bright white light, which really disturbs the behavior of the animals."

The camera weighs about 200 pounds (90 kg) and is mounted on a 7-foot (2-meter) apparatus, so the researchers felt safe leaving it unattended.

When they returned after the storm had passed, the camera was upside down.

"We don't think it was Katrina because it was 1,700 feet down," Widder said. "I think a large predator got hold of it."

The team has also photographed a fluorescent shark and said large sharks have attacked the camera in the past.

Mike Matz, of the University of Florida's Whitney Laboratory in St. Augustine, said a variety of animals have been found to use fluorescence, usually only seen in animals living at shallower depths.

"Those are little crustaceans, shrimp and planktonic copepods," he said. The light-emitting effect is seen in their eyes, on spots on their tails, at the leg joints and on the antennae," he said.

"It is fairly spectacular looking," Matz said.

Source: today.reuters.co.uk


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