Photoperiodic effects on thermoregulation in a 'blind' subterranean mammal.

Thermoregulatory responses to changes in photoperiod were studied in the 'blind' mole rat Spalax ehrenbergi (Nehring). Acclimation of cold-sensitive individuals to short photoperiod (8L:16D) at an ambient temperature (Ta) of 22 degrees C increased their thermoregulatory capacity in cold conditions, when compared to individuals which were acclimated to a photoperiod of 12L:12D at the same Ta. Acclimation of cold-resistant individuals to Ta = 17 degrees C but with a photoperiod of 16L:8D caused a decrease in thermoregulatory capacity. Evaluation of the visual pathway through the visual-evoked potentials showed that the mole rat does not respond to flash stimuli and can thus be considered to be effectively blind.