Grossniklaus-Bürgin C, Lanzrein B
Division of Animal Physiology, University of Berne, Switzerland.
Arch Insect Biochem Physiol. 1990;14(4):201-16. doi: 10.1002/arch.940140402.
The egg-larval parasitoid Chelonus sp. induces the precocious onset of metamorphosis in the 4th (penultimate) stadium of its host Trichoplusia ni, emerges from the prepupa, and then feeds on it. Qualitative and quantitative changes in ecdysteroids and juvenile hormone were measured. Hemolymph of 3rd-to 4th-instar host larvae and the parasitoids they contained, as well as nonparasitized and parasitized eggs, were analyzed. In the host hemolymph a broad peak of ecdysteroids during molting into the 4th stadium and a continuous increase from day 2 (onset of precocious wandering) until day 4 (emergence of parasitoid) were observed; 20-hydroxyecdysone and 20,26-dihydroxyecdysone were predominant. The juvenile hormone titer fluctuated in the 3rd and early 4th stadium and fell to undetectable levels shortly before the precocious onset of wandering. The parasitoid's ecdysteroids started to increase on the molt to the 2nd instar (= early 4th instar of the host) and thereafter fluctuated on a high level, 20-hydroxyecdysone, 20,26-dihydroxy-ecdysone, and ecdysone being predominant. The juvenile hormone titer was high in late 1st-instar parasitoids, decreased to low levels at ecdysis into the 2nd instar, and increased again to high levels in the 2nd-instar larvae at the time when their shape changed from flat to cylindrical. After ecdysis to the 3rd instar the juvenile hormone titer fell. A comparison revealed that both ecdysteroids and juvenile hormone fluctuate independently in parasitoid and host at most stages, suggesting that the parasitoid produces its own hormones. The first data on ecdysteroids and juvenile hormones in the egg stage of a parasitoid/host system are reported. At the stage of eye pigmentation parasitized eggs contained more immunoreactive midpolar ecdysteroids than non-parasitized ones. 20-Hydroxyecdysone and 20,26-dihydroxyecdysone were the predominant ecdysteroids in both nonparasitized and parasitized eggs, but the latter contained several additional ecdysteroids which were not seen in nonparasitized eggs. The titer of juvenile hormone was similar in both. Shortly before hatching the ecdysteroids were low in parasitized and nonparasitized eggs, but the content of juvenile hormone was much higher in the former. At this stage the majority of parasitoids have already eclosed and teratocytes are released. The results of HPLC analysis indicated the presence of juvenile hormone III together with juvenile hormones I and II in parasitized eggs, but only juvenile hormones I and II in nonparasitized eggs.
卵-幼虫寄生蜂Chelonus sp.可诱导其寄主粉纹夜蛾在倒数第二龄（即第4龄）提前进入变态期，寄生蜂从预蛹中羽化后便取食寄主。研究测定了蜕皮甾体类激素和保幼激素的定性及定量变化。分析了3龄至4龄寄主幼虫及其体内寄生蜂的血淋巴，以及未被寄生和被寄生的卵。在寄主血淋巴中，进入第4龄时蜕皮甾体类激素出现一个宽峰，从第2天（提前开始徘徊）到第4天（寄生蜂羽化）持续增加；其中20-羟基蜕皮酮和20,26-二羟基蜕皮酮占主导。保幼激素滴度在第3龄和第4龄早期波动，在提前开始徘徊前不久降至无法检测的水平。寄生蜂的蜕皮甾体类激素在蜕皮至第2龄（即寄主的第4龄早期）时开始增加，此后在高水平波动，20-羟基蜕皮酮、20,26-二羟基蜕皮酮和蜕皮酮占主导。保幼激素滴度在第1龄后期的寄生蜂中较高，蜕皮至第2龄时降至低水平，在第2龄幼虫形状从扁平变为圆柱形时又升至高水平。蜕皮至第3龄后保幼激素滴度下降。比较结果表明，在大多数阶段，寄生蜂和寄主的蜕皮甾体类激素和保幼激素均独立波动，这表明寄生蜂能产生自身的激素。报道了寄生蜂/寄主系统卵期蜕皮甾体类激素和保幼激素的首批数据。在眼色素沉着阶段，被寄生的卵比未被寄生的卵含有更多的免疫反应性中极性蜕皮甾体类激素。20-羟基蜕皮酮和20,26-二羟基蜕皮酮在未被寄生和被寄生的卵中均占主导，但后者还含有几种未在未被寄生的卵中发现的额外蜕皮甾体类激素。两者的保幼激素滴度相似。在孵化前不久，被寄生和未被寄生的卵中蜕皮甾体类激素含量都很低，但前者的保幼激素含量要高得多。在这个阶段，大多数寄生蜂已经羽化并释放出畸形细胞。高效液相色谱分析结果表明，被寄生卵中存在保幼激素III以及保幼激素I和II，而未被寄生的卵中只有保幼激素I和II。
