Body temperature regulation in the amphisbaenian Trogonophis wiegmanni

We studied the thermal ecology of the amphisbaenian Trogonophis wiegmanni at the Chafarinas Islands (North Africa). We aimed to evaluate the extent of thermoregulation in this fossorial amphisbaenian by analyzing the relationships between environmental available operative (T-e) and body (T-b) temperatures of active individuals found under stones. Amphisbaenians are typical thigmotherms that obtain heat through contact with soil and, thus, T-b was closely correlated to T-e under stones. However, the comparison of T-b with T(e)s available in the study area indicated that T-b deviated less from the set-point range of preferred temperatures than would result from a random response, which is indicative of behavioral temperature regulation. Measurements of T-e under rocks selected by T. wiegmanni deviated significantly less from the range of preferred temperatures than T-e beneath available rocks. This suggests that amphisbaenians occupied rocks with or when thermal properties were suitable for maintaining their preferred T-b. We found a bimodal pattern of T-b during the day, with amphisbaenians being active at higher T-b during the afternoon than in the morning. This did not reflect changes in the thermal environment, but was presumably a voluntary selection pattern, as indicated by similar results obtained in thermal gradients in a previous study. Also, juveniles had higher T-b than adults, but this might be a biophysical effect of differences in body size and heating rates. We conclude that amphisbaenians seem capable of regulating body temperature to an extent that comparable with epigeal diurnal lizards.