光周期对中华通草蛉自然越冬成虫及实验种群幼虫耐寒能力的影响

Effects of two different photoperiods on cold hardiness of naturally overwintering adults and laboratory-bred larvae of Chrysoperla sinica( Neuroptera: Chrysopidae)

【目的】滞育诱导期进行短光照处理可影响昆虫耐寒性。为明确光周期对中华通草蛉Chrysoperla sinica(Tjeder)耐寒性的影响,针对中华通草蛉滞育解除过程及非滞育虫态的耐寒性进行了一系列研究。【方法】测定了中华通草蛉自然越冬成虫的过冷却点(supercooling point,SCP)以及长光周期(15L∶9D)和短光周期(9L∶15D)条件下自然越冬成虫在滞育解除过程中在-12℃下的死亡率,并测定了室内长、短两种光周期下实验种群2龄和3龄幼虫的过冷却点(SCP)、结冰点(freezing point,FP)以及-7℃下的死亡率。【结果】中华通草蛉12月份的自然越冬成虫SCP集中在-10^-14℃之间。SCP低于-12℃的个体占43.70%,且-12℃处理1 d死亡率为62.00%。-12℃处理1 d条件下的长、短光周期处理自然越冬成虫,除处理0 d外,长光周期处理死亡率均高于短光周期处理的,且在处理15(P=0.012),20(P=0.01)和25 d(P=0.001)差异显著。中华通草蛉试验种群相同龄期幼虫在短光周期下的SCP和FP均高于长光周期下,但差异不显著(P>0.05);但在-7℃下,2龄幼虫短光周期下的低温死亡率为67.00%±4.04%,显著低于长光周期下的低温死亡率(78.00%±1.33%)(P=0.011),3龄幼虫短光周期条件下低温死亡率为24.33%±1.33%,显著低于长光周期下的低温死亡率(53.00%±3.46%)(P=0.002)。【结论】中华通草蛉为结冰敏感型,诱导滞育的短光照处理可提高其幼虫期及滞育解除过程中成虫的耐寒能力。

[ Aim ] Short photoperiod can influence cold hardiness of insects in diapause-inducing period. In order to clarify the effects of photoperiod on cold hardening of Chrysoperla sinica （Tjeder）, our study focused on cold hardiness of Ch. sinica adults during the process of diapause-termination and non- diapause periods. [ Methods ] The supercooling ability （ supercooling point, SCP; freezing point, FP） and the mortalities of overwintering adults from the natural population at - 12~C and the 2nd and 3rd instar larvae of the laboratory population at - 7 ℃ were investigated during adult diapause termination and induction of the long （ 15L ： 9D） and short photoperiods （9L ： 15D） in the laboratory condition, respectively. [ Results ] The SCP values of overwintering Ch. sinica adults in December were mainly distributed between - 10℃ and - 14℃. The SCP values of 43.70% overwintering adults were below - 12℃, and the mortality of overwintering adults at - 12℃ for 1 d was 62.00%. The mortalities of overwintering adults at - 12℃ treated under the long photoperiod were higher than those under the short photoperiod except those treated for 0 d, and significant difference existed among adults treated for 15,20, and 25 d. The SCP and FP values of the 2nd and 3rd instar larvae in the short photoperiod were higher but had no significant difference from those in the long photoperiod （P 〉 0. 05 ）, but the mortalities of the 2nd and 3rd instar larvae at -7℃ under the short photoperiod were 67.00% ±4.04% and 24.33%±1.33% , significantly lower than those under the long photoperiod, which were 78.00% ±1.33% and 53.00%±3.46%, respectively. [ Conclusion] The results indicate that the Ch. sinica is a freeze-intolerant insect, and its cold hardiness could be enhanced under the diapause-inducing short photoperiod.