Abstract:

Anatolica polita borealis lives in desert environment where the temperature difference varies greatly in the year around. In order to explore the cold tolerance of the beetle and its possible mechanisms, changes in the supercooling point (SCP), body water content, glycerol content, and thermal hysteresis activity (THA) of hemolymph of the adults from March to September were assayed, and the effect of 4℃ cold acclimation on its cold tolerance were also evaluated. The SCP of the larvae at different developmental stages were determined. The results showed that the SCP of adult A. polita borealis changed apparently over seasons, being －12.5℃ in March, －6℃ in July and －13.6℃ in September. Cold acclimation at 4℃ for 2 h or 24 h enhanced the cold resistance of the adult beetles at －10℃ for 40 min, and the survival rates were 70% and 90%, respectively, while it was 50% in the non-acclimated group. Body water content significantly decreased in summer compared to those in spring and autumn. The ratio of bound water to free water in March, July and September were 10.8∶1, 2.6∶1 and 5.4∶1, respectively. The regression equation of the glycerol content and the SCP of the adult was y=－0.6204x－5.681, R²=0.7714, and that of the hemolymph THA and the SCP was y=－5.26x－1.713, R²=0.9049, showing that the hemolymph THA had more effect on the decrease of the SCP of the adult than the glycerol content did. The SCP of the larvae decreased with the larval development. The results suggest that A. polita borealis obtains high cold tolerance by keeping low SCP via increasing the ratio of bound water to free water and the amount of antifreeze protein and glycerol.

Key words: Anatolica polita borealis, cold tolerance, supercooling point, thermal hysteresis activity, water content, physiological mechanisms