Snouts: A star is born in a very odd way 

 During fetal development in star-nosed moles, little cylinders form on the sides of the face surrounding the two nostrils. (Catania) The 22 pink rays that sprout from the snout of the star-nosed mole develop in a way unlike any other animal appendage, a Tennessee-based research team says.

 The wiggling, touch-sensitive nose rays don't bud straight out from the body wall-the basic strategy for human limbs, insect legs, fish fins, sea urchin spines, and a huge range of other animal equipment, reports Kenneth C. Catania of Vanderbilt University in Nashville.

 Instead, the sides of the mole's face swell into ridges that round into fat little cylinders embedded in the skin. After the moles are born, the cylinders come loose at the back end and spring forward to form the species' distinctive nose fringe.

 In a sense, the rays end up backwards. Adult tissue that once lay toward the rear of the face turns into the ray tip, and what had been at the front becomes the ray's base. Catania and his colleagues document the process, with images of fetal and newborn moles, in the Sept. 30 Journal of Experimental Biology.

"Why would you peel up an appendage from the side of your face instead of growing it out, the way everybody else in the universe does it?" asks Catania.

 This novelty offers a great opportunity for molecular investigation, he argues. The outgrowths in all other creatures so far studied rely on the same genetic tool kit, even in organisms as different as fruit flies and people. Does the mole nose's oddball development come from some novel function of these same genes? Or does the peculiarity signal a different suite of genes for limb formation?

"It's going to be interesting either way," comments Grace Panganiban of the University of Wisconsin-Madison, who studies the genetics of development. Like the Tennessee researchers, she can't think of a similar developmental trajectory. Catania's description was "fascinating," she says, and she, too, wants to know the molecular mechanisms.

 A mature mole's nose checks out the world with 100,000 nerve fibers, outdoing the 17,000 or so in a human hand. (Catania)

 The reversed orientation of the nose rays intrigues Catania. "If you were an engineer drawing on a chalkboard, you would never think of developing limbs that way," he says. "When you can point to something that's done in a stupid way," it may signal how the process evolved, retaining bits of previous systems. Catania suspects that he's found a trace of history in a different mole species. It develops sensory strips on its snout, but they don't burst into stars.

 Exotic as a star-nosed mole looks, the species burrows through most wetlands in the northeastern United States and ranges into Canada. The nose, with abundant nerves and skin only one-twentieth as thick as a person's, gives these moles what Catania ranks as "the most developed sense of touch of any mammal on the planet."