Cold resistance and adaptation of Pyrrhocoris apterus

This study aimed to investigate the cold tolerance and adaptation strategy of Pyrrhocoris apterus（ Heteroptera:Pyrrhocoridae） during the over-wintering period. The supercooling point（ SCP） of the wild population（ control group） and the cold acclimation group,the survival rate under low temperature,LT50 and the content of biochemical substances were determined from December of 2015 to March of 2016. The results showed that the minimum SCP was（-14.01±0.53） ℃ in the wild population,whereas that in the population treated at -5 or -10℃ for 30 min were（-19. 32 ± 0. 86） ℃ and（-25.56±1.09） ℃,respectively. After treatment at 0℃ for 30 min,followed by exposure to -5,-10 or-15℃ for 1 h,the maximum survival rates of P. apterus were 100%,39.1% ±8.6% and 10%,respectively. The minimum LT50 of the wild and acclimated populations at 0℃ for 30 min were -8. 53℃ and -9. 21℃,respectively. The free/combined water and free protein content of P. apterus females and males initially decreased,and then increased,to reach the maximum in December（ 144.504±26.219 and 140.317±21.92,（ 15.8102±0.0992） and（ 15.4688±0.01475） mg/g,respectively）. Fat,trehalose and glycerol content of P. apterus females and males first increased,and then decreased,reaching the maximum in February during the over-wintering period. The fat content for females and males were（ 16. 33 ± 0. 48） and（ 13. 15 ± 1. 32） mg/g,respectively. The trehalose content was（ 11.98±0.01） and（ 10.88±0.02） mg/g,respectively,and the glycerol content was（ 14.74±0.01） and（ 15.06±0.03） mg/g,respectively,in female and male P. apterus. The present study demonstrated that acclimation could lower the SCP and LT50 of P. apterus than those in the wild population. These results indicated that acclimation could improve the survival rate and enhance cold resistance in P. apterus by modulating the content of cryoprotectants during the over-wintering periods.