The parietal eye and thermoregulatory behavior of Crotaphytus collaris (Squamata: Iguanidae)

Abstract

1. 1. Male Crotaphytus collaris with shielded parietal eyes, sham shielded parietal eyes and non-shielded controls acclimatized to 25 ± 1°C and an LD 12:12 photoperiod did not select significantly different body temperatures over a 24 hr period with uniform light (UL) over a linear thermal gradient, a point-source of light over the hot end (LH) or a point-source of light over the cold end of the gradient (LC). 2. 2. Mean body temperatures of the shielded LH lizards from 2100 to 0900 hr (32.1 ± 0.70°C) were significantly higher ( P < 0.05) than those of the non-shielded LH lizards (28.6 ± 0.86°C). 3. 3. Diel cycles of temperature selection were observed in all 3 UL groups and in the non-shielded LH group but not in the shielded LH or any of the LC groups. 4. 4. The parietal eye did not have an effect on thermoregulatory precision, but did affect diel cycles of temperature selection and, in the LH groups, body temperatures during scotophase.