Whale's tusk is packed with sensory nerves

In Brief

Nature

December 16, 2005|By BLOOMBERG NEWS SERVICE

In a new twist on the legendary narwhal's tusk, a study suggests that it's bristling with nerves sensitive to the Arctic whale's environment and food supply.

Males and some female whales brandish a single corkscrew tooth with 10 million nerve connections that may sense changes in water temperature, pressure and saltiness, as well as act as a dinner bell, according to research presented this week at a conference in San Diego.

The ivory tusk's strength and flexibility - it can bend about a foot in any direction - is unique, investigators said. The results may lead to more durable composite dental fillings for people, according to lead investigator Martin Nweeia, who said the study was a product of "pure childhood curiosity."

"The fact we see this in an Arctic environment is completely counterintuitive," said Nweeia of Harvard's School of Dental Medicine. "Why would you go out of your way to have 10,000 sensory connections in an animal that might be more likely to insulate itself from the environment?"

The creatures, found in the dark waters off the coasts of Greenland, North America and Russia, fade to ghostly white as they age, the scientists said. Narwhals dive as deep as 3,281 feet (1,000 meters), though they surface every 20 minutes or so to breathe, Nweeia said.

Detecting the saltiness of the sea tells whales when ice is being formed and when they need to leave an area to avoid being trapped. Particles may also indicate when food is present, Nweeia said. The narwhals' menu includes squid, shrimp, halibut and rockfish.

The narwhals' "tusking" behavior, in which males rub tusks, is another possible use for those tender nerve endings, according to results Nweeia presented at the 16th Biennial Conference on the Biology of Marine Mammals. Other scientists have proposed that the tooth, which sprouts from the narwhal's left upper jaw, might be used in displays of male aggression, or as an ornament during courtship of mates.

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