铅胁迫对甜菜夜蛾连续五代生殖力的影响研究

Effect of lead stress on the fecundity of five successive generations of the beet armyworm

【目的】甜菜夜蛾Spodoptera exigua是蔬菜等作物上的主要害虫,而蔬菜地常会遭到重金属的污染和侵蚀。本文系统探究了重金属铅对甜菜夜蛾多个世代生殖力的影响,为评价重金属污染对昆虫等生物的长期累积效应提供依据。【方法】人工饲料中添加一定量的Pb(NO_3)_2溶液,配制成浓度为0(CK)、0.3、4.8、76.8 mg/kg的Pb^(2+)饲料连续饲养甜菜夜蛾5个世代,研究不同浓度的铅胁迫对该虫生殖力的系统影响。【结果】随着饲养世代的延续和铅浓度的增加,会使甜菜夜蛾的雌雄比出现分化,且呈现浓度优势现象。特别是饲养到第3、4代,高浓度铅胁迫后,甜菜夜蛾的雌性比达到60%以上,与对照比差异显著;甜菜夜蛾的生殖腺指数、产卵量和卵的孵化率也与工人饲料中铅的浓度及饲养世代数密切相关:总的表现为饲养世代数越长、铅浓度越大,该虫的生殖腺指数越小、产卵量越少、卵的孵化率越低。以最高浓度(76.8 mg/kg)的铅处理甜菜夜蛾5个世代为例,生殖腺指数仅是对照组的60.4%,产卵量与卵的孵化率分别是对照处理的60.5%和46.2%。【结论】铅胁迫对甜菜夜蛾生殖力影响的程度与重金属浓度及污染的世代数有关。

[Objectives] To understand the effect of lead on the fecundity of the beet armyworm. [Methods] the effects of different concentrations of dietary lead （0, 0.3, 4.8, 76.8 mg/kg） on the fecundity of five successive generations of the beet armyworm were measured and compared. [Results] Increased lead concentration affected the sex ratio of later generations, especially the 3rd and 4th generations in which the proportion of female offspring reached 50% at high dietary lead concentrations, significantly higher than in the control. The production gland index, number of eggs and hatching rate were also highly correlated with lead concentration and generation; the more generations and the higher the lead concentration, the smaller the production gland index, the lower the number of eggs produced and the lower the hatching rate. Compared to the control group, the high lead （76.8 mg/kg） treatment group had significantly reduced gonad and oviposition indices. The gonad index was just 60.4% that of the control, whereas the number of eggs laid and the hatching rate were 60.5% and 6.2% those of the corresponding control group. [Conclusion] The effect of dietary lead on the fecundity of the beet armyworm increased with the lead content of the diet and generation.