About 10% of rodent species have adapted to subterranean live style. Some of the challenges faced by these animals are the risks of overheating, lack of oxygen (hypoxia) and high levels of carbon dioxide (hypercapnia). Some of the key adaptations these species have developed are low resting metabolic rate and low core body temperature.

Unusually low serum concentrations
It has been shown in previous studies that the Ansell’s mole-rat (Fukomys anselli), as well as the African mole-rats (Heterocephalus glaber), have unusually low serum concentrations of the thyroid hormone T4, so much that it is more in line with poikilothermic reptiles rather than mammals. In a recent study, researchers looked at what effect raising the serum thyroid hormones had on resting metabolic rate and body temperature in Ansell’s mole-rats.

Core body temperature measured with DST nano-T
Scientists from the University of Duisburg, Charité – Universitätsmedizin Berlin, and German Centre for the Protection of Laboratory Animals implanted 15 non-reproductive Ansell’s mole-rats with Star-Oddi DST nano-T temperature loggers in the abdominal cavity, 5 females and 10 males. The loggers were set to measure core body temperature every 20 minutes throughout the whole treatment period to investigate the effects of increasing thyroid hormone on body temperature.

Higher body temperature seen with T4 treatment
The research team worked from the hypothesis that T4 treatment would result in higher resting metabolic rate, increased core body temperature and heat dissipation. Surprisingly the effects of the treatment were not as pronounced in the female mole-rats as in the males. Different statistical tests showed significantly higher body temperature in the T4 treated animals. It was however significantly more effective in the male rats compared to the females. Also, the trend of heat dissipation from the ventral or abdominal was also higher in the male rats compared to the females.

Further tests were performed, all results can be found in the article published in Frontiers in Endocrinology and can be found here.

Photo: iNaturalist