The haemolymph of larvae of Tenebrio molitor contains a factor which produces a thermal hysteresis (a difference between the freezing and melting points) of approximately 0.75 °C. When larvae were acclimated to low temperatures or short photoperiod the thermal hysteresis increased more than twofold. Coincident with the increase in thermal hysteresis the supercooling points and lower lethal temperatures of the larvae were depressed. Therefore, the thermal-hysteresis-producing factor seems to function as an antifreeze.
The factor may also act as an adaptation to prevent desiccation. Thermal hysteresis increased almost three-fold in larvae acclimated to low relative humidity. Also, larvae with high levels of the thermal hysteresis factor survived low relative humidities much better than did larvae with lower levels.
- © 1978 by Company of Biologists