`Definitely the strangest animal'

Discovery: Among the bones of dead whales, a unique worm is at work devouring nutrients from carcasses.

Medicine & Science

August 02, 2004|By Glennda Chui | Glennda Chui,KNIGHT RIDDER/TRIBUNE

The only good whale is a dead whale - at least from the standpoint of two of the weirdest creatures known to science, which make a living devouring whale bones on the floor of Monterey Bay in California.

They're worms, but they look almost like plants, sending roots deep into whale skeletons to draw out nutritious fats and oils. They're full of bacteria that help them digest this bounty.

And the female worms, which are an inch or two long, harbor dozens of microscopic males inside their bodies - 111 of them, in one case. The male worms are little more than sacks of sperm. They have no way to eat, but they live off scraps of yolk left from the eggs that hatched them; when it runs out, they die.

It may be that worm larvae that land on bones develop into females, while those that land on female worms develop into male worms, said Robert C. Vrijenhoek, an evolutionary biologist and geneticist at the Monterey Bay Aquarium Research Institute who led the team that discovered the worms. But that's pure speculation.

"It is definitely the strangest animal I've ever seen," said Craig Smith, a biological oceanographer at the University of Hawaii and an authority on the bizarre communities of animals that spring up on whale remains.

The two new species of worms, each topped by feathery red plumes, are described in today's issue of the journal Science. They were found on the carcass of a young gray whale that sank to the bottom of Monterey Canyon in nearly 9,500 feet of water. When scientists found it in February 2002, most of the meat was gone, but the skeleton, intestines and some of the skin and fins were still intact.

They've been visiting the remains every few months, using a robotic submersible to take pictures and samples.

Dead whales are more than a scientific curiosity. Each is an oasis in the vastness of the deep sea, supporting vibrant communities of animals that may persist 50 to 100 years.

Some researchers have suggested that these so-called whale falls serve as steppingstones, allowing animals to spread from the shallows into the depths or from one hydrothermal vent to another.

Of the 407 species that have been discovered around whale carcasses, some also live around hydrothermal vents, where hot, mineral-rich water spews from the sea floor, Smith said. Others are found near seeps of cold water on the ocean bottom.

But so far, 24 species have been seen only around dead whales, Smith said. Many other creatures that lived on whale falls may already have become extinct as a result of intensive whaling, which reduced populations of great whales by 90 percent.

Smith estimates that there are nearly 800,000 dead whales on the ocean floor, each contributing a big, blubbery windfall.

Dead whales go through three stages, Smith said.

First sharks and other scavengers strip off the meat, reducing a 30-ton whale to a skeleton in less than 18 months.

Then worms, crustaceans and other animals settle on the carcass and in the surrounding mud.

Finally, bacteria break down the bones, releasing sulfur compounds that feed tube worms, clams, mussels and other animals. Whale bones are up to 60 percent fat by weight, so they're a rich source of food.

About a dozen carcasses have been discovered in the past few years; an additional 10 or 15 skeletons have been dredged up from the bottom with their communities of animals intact.

In addition, researchers sometimes deliberately sink whales that wash up dead, marking them with electronic beacons so they can be easily relocated.

But the latest find was accidental. Vrijenhoek said his team stumbled onto the carcass while looking for clams in Monterey Bay.

The two new worm species, which belong to a new genus called Osedax - meaning "bone-devouring" - are distant relatives of the tube worms found around hydrothermal vents and cold seeps, Vrijenhoek said.

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