(Philadelphia, PA) Otters cavorting in the water is a scene with which we're all familiar. Yet, unlike many other mammals that spend a considerable amount of time in the waterpolar bears, seals, dolphins, and whalesriver otters do not have a thick layer of body fat to keep warm. They rely, instead, on a few unique adaptations; namely, their fur and the densely packed layer of specially adapted underhairs.
Using scanning electron microscopy and polarizing light microsopy, John W. Weisel, PhD, Professor of Cell and Developmental Biology at the University of Pennsylvania School of Medicine, and colleagues, examined the structure of these hairs for clues to their exceptional insulation abilities. They found that the cuticle surface structure of the underhairs and base of the less-abundant guard hairs are distinctively shaped to interlock, with wedge-shaped fins or petals fitting into wedge-shaped grooves between fins of adjacent hairs. Weisel and colleagues report their findings in the Canadian Journal of Zoology.
Weisel and Research Specialist Chandrasekaran Nagaswami, MD, also in Penn's Department of Cell and Developmental Biology, usually work on defining the physical properties of blood clots and applying this knowledge to find better treatments for heart disease. Two years ago when Weisel, an avid hiker, climber, and white-water kayaker, took a month of his sabbatical year to study wolvesa life-long intereston Isle Royale National Park in Lake Superior, Michigan, he also collected hair samples from the island's mammals--including wolves, moose, and otters. (The ecological studies of wolves and moose on Isle Royale, which started in 1959, are part of the longest-running animal ecology study in the world. Isle Royale has been a training ground for many ecologists, and lessons learned here have been applied to the re-introduction of wolves to Yellowstone National Park.)