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Antarctic unsavory to shipworms: currents and polar front keep destructive mollusks at bay.

Quirks of ocean currents may have turned the waters around Antarctica into a rare sanctuary for wooden shipwrecks, free of the destructive mollusks known as shipworms.

A front formed by the junction of frigid polar and warmer waters as well as a strong current circling the continent may block tiny shipworm youngsters from moving in, says Thomas Dahlgren of Uni Research, the University of Bergen's partner research company in Norway.

Fourteen months after leaving wooden planks and whale bones underwater on western Antarctica's continental shelf, researchers found no evidence of wood-boring mollusks. Whale remains attracted bone-eating worms but the wood emerged "pristine," Dahlgren and his colleagues report August 14 in the Proceedings of the Royal Society B.

Offshore Antarctica is a terrible habitat for wood borers because the continent probably hasn't grown trees for at least 30 million years. And research on other marine species has suggested that the Antarctic circumpolar current and the polar front can block some invaders from moving in.

If more exploration confirms the dearth of wood-boring mollusks, Antarctica would join the Black and Baltic seas as the main gaps in the world's shipworm map--for now. "Invasive shipworms are now entering the Baltic and may well be threatening ancient shipwrecks," says Janet Voight, a curator at the Field Museum of Natural History in Chicago.

Sea-sunken timber can attract mollusks called teredinids, with long wormy bodies sticking out of shells, and the more depth-loving xylophagains. These deeper-dwelling wood-borers live much like the Osedaxworms that bore into whale bones on the ocean floor, says marine evolutionary biologist Kenneth Halanych of Auburn University in Alabama.

The submerged whale bones attracted Osedax worms. At least two kinds are species new to science, apparently relying on microbes to extract nutrients from fallen carcasses.

Caption: A study in Antarctic waters turned up a new species of worm, Osedax antarcticus, that feeds on the bones of dead whales.


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Author:Milius, Susan
Publication:Science News
Geographic Code:8ANTA
Date:Sep 21, 2013
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