Threat to Glass-Eating Turtle

The hawksbill turtle, which thrives by munching glass-covered, poisonous sponges, is being threatened with extinction by an international market for tortoise shell trinkets.

But despite its robust eating habits, the hawksbill has become the second most endangered marine turtle in the world because the shell is a popular fashion, according to researcher Anne Meylan of the Bureau of Marine Research in St. Petersburg, Fla.

She said the turtle dines almost exclusively on coral reef sponges that are covered with a type of opal glass. The glass breaks up into sharp needlelike crystals that the turtle swallows and digests with no apparent ill effect.

The sponges also contain a poison that is deadly to humans and to most other animals, but the hawksbill actually stores it in his flesh, Meylan said in a report last month in Science magazine.

Little was known about the hawksbill’s diet until Meylan started examining carcasses of turtles caught by fishermen in Panama and the Caribbean.

She quickly found that autopsies on the hawksbill can be dangerous because the gut usually is filled with microscopic glass flakes called specules.

“The little glass specules are sharp, and they have hooks and barbs,” Meylan said. “They are little daggers that go right through your skin.”

Yet, she said, the hawksbill seems to not get so much as a tummy ache as the glass passes through its digestive tract.

“The glass becomes more and more concentrated as the organic matter is stripped away by regular digestive processes,” Meylan said. “By the end of the digestive tract, the feces are almost solid glass.”

Powerful poisons in the flesh of the sponges is stored in the hawksbill’s muscle and fat where it poses a deadly threat to humans who use the turtle for food.