低温对蝶蛹金小蜂卵成熟及其数量动态的影响

Effects of the low temperature treatment on egg maturation and its numerical dynamics in the parasitoid Pteromalus puparum(Hymenoptera: Pteromalidae)

寄生蜂卵成熟动态影响其产卵决策行为,因而对于认识寄生蜂搜寻行为生态学机理具有重要意义。以蝶蛹金小蜂(Pteromalus puparum)-菜粉蝶(Pieris rapae)为模式生物,首先连续3周每隔24 h详细观察子代蜂幼期不同发育阶段的体型、卵巢管以及寄主蛹的外部形态,以此为基础观察了低温处理(模拟越冬温度)被寄生蛹对子代蜂成熟卵数量动态的影响。蝶蛹金小蜂胚后发育历时约2周,其中卵期1 d;幼虫历期约7 d。初孵幼虫体透明;胚后第3—6天体积快速增大,然后减缓,体色由绿变黄;胚后第8天进入预蛹,第9—12天蛹淡色,复眼由淡黄变为深红,第13—14天蛹暗黑色,并逐渐带有金属光泽。卵巢管在羽化当天即开始沉积卵黄,并在羽化后1—4 d连续增加直到出现卵吸收;羽化后5—6 d成熟卵数量增速不明显甚至略有减小。寄主蛹随子代蜂从卵发育至幼虫再到蛹体色从绿色变为灰褐色再到土黄色。低温处理被寄生的寄主蛹(寄生蜂处于老熟幼虫或蛹期)后,羽化成虫的卵巢管略细,成熟卵数量较少。成熟卵数量的变化不仅受低温处理的影响,而且受雌蜂体型大小和日龄的影响;低温处理明显减缓卵成熟速率,各日龄期成熟卵数量均明显减少;适温下成熟卵数量于羽化后第4天达到峰值,而低温处理下成熟卵数量达到峰值的时间延迟至第7天。研究表明,越冬低温对来年羽化的蝶蛹金小蜂卵成熟动态具有不良影响。

Egg maturation dynamics is closely associated with oviposition decision behaviors in parasitoids.So,it is necessary to understand egg maturation dynamics and factors that may affect it with the goal of revealing characteristics of reproduction ecology.The present study,using the gregarious parasitoid,Pteromalus puparum and host Pieris rapae pupa as the model system,was undertaken first to describe daily changes in external morphology of postembryonic stages,and then to observe daily variations in number of mature eggs in adult parasitoids emerged from host pupae that previously received the treatment of low temperature.The postembryonic development took about 2 weeks,where egg stage lasted for 1 day and larva 7 days.Neonate larva was clear,and grew rapidly with body color from green to yellow during next 3—6 days.Prepupal stage appeared 8 days later in light color,and the eye color changed from pale yellow to dark red 9—12 days later.Pupa was dark in color with metallic luster on day 13—14.Egg yolk appeared in ovarioles on the same day of adult emergence,and increased during a next few days until osorption.Mature eggs did not obviously increase,or even decreased slightly during first 4—5 days after adult emergence.The host pupa,following development of the progeny parasitoid from egg to larva and pupa,varied in color from green to light brown and then to yellowish brown.Ovarioles were thinner and total matured eggs fewer in parasitoids receiving the low temperature（5℃） treatment than those from the control（25℃）.Egg maturation was not only influenced by the low temperature,but also by female body size and age.The low temperature treatment markedly reduced egg maturation progress,resulting in fewer daily mature eggs than did the optimal temperature treatment.The peak time for mature eggs appeared on the 4th day after adult emergence under the low temperature treatment,but as late as the 7th day under the optimal temperature treatment.Number of mature eggs increased with female body size under both optimal and low temperature treatments.This study suggests that egg maturation dynamics can be affected not only by low temperature on parasitized host pupae but also by female body size and age.