SCIENCE

Notebook

Moles Detect Scents Underwater

Common scientific wisdom has it that mammals cannot smell underwater -- that when they adapt to an aquatic life their sense of smell gradually disappears. But new research into the underwater olfactory abilities of the star-nosed mole and the water shrew has concluded that these semiaquatic animals actually can smell underwater. Even more remarkable is the way they do it: by blowing air bubbles out their nostrils and then sucking them back in.

After noticing the bubbles, researcher Kenneth Catania of Vanderbilt University set up a high-speed camera beneath the glass tank and began filming. He found that the animals exhaled and inhaled the bubbles five to 10 times a second, about the same rate as the sniffing behavior of a similarly sized land mammal, such as a rat or a mouse. Catania placed a number of objects -- some edible and some not -- on the floor of the tank and watched the mole. He found that when the animals approached one of the objects, they would blow bubbles that made contact with the objects and then were sucked back into the nostrils.

The star-nosed moles were further tested in an underwater course that had a trail of fish or earthworm scent. Since the moles can use the ultra-sensitive star appendages that surround their noses almost like fingers, a thin grid was placed between the animals and the trail to make sure they were only smelling -- rather than touching -- the scent. Five moles were able to follow the earthworm smell accurately 75 to 100 percent of the time, and two moles followed the fish smell 85 to 100 percent of the time. When an even finer grid was used -- one that interrupted the mole's bubble-smelling system -- the rate of success fell to simple chance.

The findings were reported in the journal Nature.

-- Marc Kaufman

Shark Aids Human Genome

Humans have more in common genetically with elephant sharks than with some other fish species, according to a new paper published Friday in the journal Science.

Twelve scientists in Singapore and the United States have generated a genome sequence for the elephant shark, one of the most primitive jawed vertebrates, and have compared it with the human genome sequence to examine key elements that help regulate the expression of genes in vertebrates. The elephant shark and other related species diverged from humans about 530 million years ago, while teleost fish such as zebra fish split off about 450 million years ago. Despite this, the sequence showed humans had twice as many of these non-coding elements in common with elephant sharks as with teleost fish.

Ewen F. Kirkness, an investigator at the Institute for Genomic Research in Rockville, and one of the paper's co-authors, said in an interview Friday that the findings suggest teleost fish species evolved faster than some shark species. This research also gives scientists clues on what aspects of the human genome they should explore in future studies.

"It tells us where we should be looking for in terms of regions of the human genome that have been conserved for vast amounts of time, and therefore we assume have important functions," Kirkness said. "This is really just the start."