| Due to the limitation of the environmental conditions, many parasitic wasps resorb the ovum nutrients to survive. Therefore, the parasitic wasps should have the ability to independently control the generation and developmental progress of ova in their body according to environment conditions.However, there are a few documents to prove it. In this study, we chose three parasitoid species Encarsia sophia, Encarsia formosa and Eretmocerus hayati with different reproductive modes, and investigated the dynamical change of ovum development after feeding on whitefly hosts and honey solution. The main results obtained as followed:1、The eggs of three parasitoid species were all divided into three grades.Three parasitoid species have similar grade I eggs, spherical, and about 22μm in diameter. The grade II and grade III eggs of En. sophia were long elliptic, 148 and 179 μm in length, respectively. Similarly, the grade II and grade III eggs of En. formosa were long elliptic, 100 and 130 μm in length, respectively. However, the grade II eggs and grade III eggs of Er. hayati were short elliptic. 185 and 1115 μm in length, respectively.2、Mature eggs(grade III) of mated and unmated En. sophia after feeding on Bemisia tabaci nymphs and honey solution had completely different variation trends. 12 h after feeding on whitefly nymphs, the number of mature eggs of mated females(5.4) was significantly higher than that of unmated females(2.7), and 24 h after feeding on whitefly nymphs, total number of various grade eggs(9.2) and number of mature eggs(4.9) of mated females was significantly higher than those of unmated females. However, 12 h after feeding on honey solution, the number of mature eggs of mated females decreased, which indicated that some of mature eggs were resorbed to sustain their lives. The results indicated that En. sophia females could independently control ovum development according to host species faced and their own nutritional situation.3、0, 12, 24 h after feeding on B. tabaci nymphs, the numbers of mature eggs in En. formosa females were 4.3, 7.7, 5.5, respectively, significantly higher than those of individuals fed on honey solution and without any feeding. 12 h after feeding on B. tabaci nymphs, total number of various grade eggs was 16.5, significantly higher than those of individuals fed on honey solution and without any feeding. 24 h after feeding, there was no difference in total number of various grade eggs between the females fed on whitefly nymphs(13.2) and honey solution(12.0). The decrease of mature eggs in females without any feeding indicated that nutrition of ova was resorbed to sustain life in En. formosa. The results indicated that host feeding on whitefly nymphs could improve ovum mature and oogenesis in En. formosa; feeding on honey solution could also improve their oogenesis; En. formosa could independently control ovum development according to their own nutritional situation. In addition, there was no difference in longevity of En. formosa fed on honey solution(84 h) and whitefly nymphs(78 h) for 12 h..4、0 h after feeding on B. tabaci nymphs, the number of mature eggs in Er. hayati females was 36.8, significantly higher than that of individuals fed on Trialeurodes vaporariorum nymphs(27.3). 24 h after feeding on B. tabaci nymphs, total number of various grade eggs(50.6) and number of mature eggs(44.6) in Er. hayati females were significantly higher than those of individuals fed on T. vaporariorum nymphs and honey solution. 24 h after starvation, the number of mature eggs decreased to 25.4 from the initial 30.7 eggs, which indicating that some of mature eggs were resorbed to sustain their lives. The results indicated that Er. hayati could independently control ovum development according to host species faced and their own nutritional situation, and feeding on B. tabaci nymphs could improve their ovum mature and oogenesis. In addition, Er. hayati survived for 100 h after feeding on honey solution for 12 h, significantly longer than that of individuals fed on whitefly nymphs, which indicated that feeding on non-host foods(honey solution) could significantly extend their longevity.On the whole, three whitefly parasitoid species with different reproductive modes have the ability of independent control ovum development. Under the starvation, all three parasitoid species could resorb the nutrition of ova to sustain their lives. The nutrition from feeding on whitefly hosts could improve their ovum mature and oogenesis. Whereas feeding on non-host food... |
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