Researchers said it was too early to know whether the oil came from the BP spill, but about 40 percent of the area where the crab larvae were found has been affected by oil gushing from the broken deepwater well. The orange spots have been detected in crabs across the northern Gulf coast, from southwestern Louisiana to Pensacola, Fla.
"In my 42 years of studying crabs I've never seen this," said Harriet Perry, a biologist with the University of Southern Mississippi's Gulf Coast Research Laboratory.
Perry and scientists with Tulane University noticed the blotches while analyzing water and plankton samples during the early stages of research to determine whether the oil is hurting the crabs - which at this point is uncertain.
Crabs are especially sensitive to contamination during their larval stages, said Vince Guillory, a biologist with the Louisiana Department of Wildlife and Fisheries. It's too early to tell how the oil-affected larvae will affect future adult populations.
Chemical dispersants or other substances may be partly responsible for the spotting, said biologist Caz Taylor of Tulane University, who is investigating that possibility.
After hatching close to shore, crab larvae drift into open waters and go through several stages. While only about a tenth of an inch long, they move back toward the coastal estuaries where they grow to adulthood. The researchers found the oil droplets on larvae at that barely visible stage.
The discovery has implications for the entire Gulf food chain because crab larvae are prey for many kinds of fish as well as raccoons and endangered whooping cranes, Perry said.
"They are a keystone species," she said. "If we have a loss of blue crabs, we're looking at a loss of everything."