National Geographic : 2011 Nov
NOW PHOTO: WOLF HANKE, MARINE SCIENCE CENTER, UNIVERSITY OF ROSTOCK. ART: MARC JOHNS KOI STORY Legend has it that a fish named Hanako was the world's longest lived. After swimming for 226 years in Japan, the story goes, the scarlet koi died in 1977. Her scales were said to determine her elderly age---a notion that holds water with science today. Much as trees have rings, fish have micro- scopic "zones" within their scales that reflect seasonal growth patterns. In summer, when food is abundant, fish grow quickly and produce wide zones. Winter lines are narrow. A pair of zones represents one year. In Hanako's case, adding them up must have taken an eternity. ---Catherine Zuckerman Whiskers at Work Not much gets by a harbor seal. That's because its whiskers, or vibrissae, pick up highly detailed data about the animal's environment. A seal's snout hairs protrude from follicles containing about ten times as many nerve endings as a rat's sensitive whiskers. Sensory biologist Wolf Hanke of the University of Rostock says seal vibrissae have adapted over 25 million-plus years to read minute changes in water movement. Hanke and colleagues study this phenomenon with Henry, a trained harbor seal (above). Wearing a blindfold and headphones, Henry has shown that he can detect the traces of an object in calm water even 30 seconds after the object has passed. And the latest trials reveal that he can also distinguish among shapes and sizes---using just his whiskers. Other species likely share this ability, which, Hanke posits, helps seals nab darting fish. It even lets them "see" the meatiest prey in the murkiest waters, for a more fruitful chase. ---Jennifer S. Holland A harbor seal named Henry is outfitted for sensory studies at a lab in Rostock, Germany.