Thermoconforming rays of the star-nosed mole

Abstract

The star-nosed mole (Condylura cristata) is well known for its unique star-like rostrum ("star") which is formed by 22 nasal appendages highly specialised for tactile sensation. As a northerly distributed insectivorous mammal occupying both aquatic and terrestrial habitats, this sensory appendage is regularly exposed to cold water and thermally conductive soil, leading us to ask whether the surface temperature, a proxy for blood flow to the star, conforms to the local ambient temperatures as a means to conserve body heat. Alternatively, given the high functioning and sensory nature of the star, we posited it was possible that the rays may be kept continually warm when foraging, with augmented peripheral blood flow serving this tactile sensory organ. To test these ideas, we remotely monitored the surface temperatures of the star and other uninsulated appendages in response to changes in local water or ground temperature in wild-caught star-nosed moles briefly studied in captive situation. While the tail responded to increasing heat load through vasodilation, the surface temperature of the star consistently thermoconformed, effectively passively varying in surface temperature, suggesting little evidence for thermoregulatory vasomotion. This thermoconforming response may have evolved as a compensatory response related to the high costs of heat dissipation to water or soil in this actively foraging insectivore.