阶段性极端高温对七星瓢虫生长发育和繁殖的影响

Effects of periodical extremely high temperature on the growth,development and reproduction of sevenspotted lady beetle Coccinella septempunctata

为明确极端高温天气对七星瓢虫Coccinella septempunctata生长发育和繁殖的影响,通过模拟田间高温发生情况,设置6 h极端高温(36℃和39℃)与不同持续时间(1 d和3 d)对七星瓢虫卵和成虫进行胁迫,以25℃恒温饲养处理为对照,观察统计其发育历期、存活率、繁殖力及子代孵化率。结果表明,在相同高温胁迫模式下,七星瓢虫成虫的耐热性要明显高于卵,如在39℃处理1 d后,卵和成虫的存活率分别为52.09%和93.94%;处理温度越高,高温持续时间越长,七星瓢虫卵的存活率越低,36℃处理1、3 d和39℃处理1、3 d后卵的存活率依次为71.31%、62.87%、52.09%和24.98%。七星瓢虫卵经39℃处理3 d后,其孵化1龄幼虫的发育历期为2.77 d,显著长于对照组(2.11 d),其余龄期幼虫的发育历期、整个幼虫期和蛹期与对照组均无显著差异,说明七星瓢虫发育前期经历极端高温可能会导致其发育后期生长加速,出现生长补偿现象。卵期受极端高温的影响要显著大于成虫期,卵和成虫在39℃处理1 d后的单雌产卵量分别为42.67粒和139.79粒;所有高温处理组的子代卵孵化率均显著低于对照组(85.42%),介于0~64.13%之间。另外,各高温处理组的种群趋势指数在5.26~56.02之间,均低于对照组(78.76)。表明夏季极端高温天气频发可能导致七星瓢虫种群数量减少,不建议此时期在田间释放七星瓢虫卵进行害虫防控。

In order to evaluate the effect of extremely high temperature on the development and reproduction of sevenspotted lady beetle Coccinella septempunctata,the condition of high-temperature field was simulated by setting 6-h extreme heat(36℃and 39℃)and different durations(1 d and 3 d)to put the eggs and adults of C.septempunctata under stress,and the condition under 25℃was used as the control.The developmental duration,survival rate,fecundity and hatchability of offspring were observed and calculated.The results showed that,under the same stress pattern,the heat tolerance of adult was significantly higher than that of egg.For example,the survival rates of egg and adult were 52.09%and 93.94%,respectively,after being treated at 39℃for one day.Under the same insect state,the survival rate of C.septempunctata eggs was lower with increasing treatment temperature and time,and the survival rates of egg under four stress patterns(36℃for 1 d and 3 d,39℃for 1 d and 3 d)were71.31%,62.87%,52.09%and 24.98%,respectively.When the eggs were treated at 39℃for three days,the developmental duration of the first-instar larvae was 2.77 d,which was significantly longer than the control(2.11 d),but the entire larval stage and pupal stage was not significantly different from the control.It was suggested that the extremely high temperature experienced by C.septempunctata in the early stage of development might lead to the acceleration of its growth in the later stage of development or a phenomenon of growth compensation.The effect of extremely high temperature on egg stage was significantly greater than that on adult stage.The eggs laid were 42.67 and 139.79,respectively,when the egg and adult were treated at 39℃for one day.The hatchability of offspring in all treatment groups was significantly lower than that of the control(85.42%),ranging from 0 to 64.13%.In addition,the population trend index of each treatment group was 5.26-56.02,which was lower than that of the control group(78.76).Therefore,the frequent occurrence of extremely high temperature in summer might reduce the population of C.septempunctata,and it is not recommended to release C.septempunctata eggs in the field for pest control during this period.