四环素对孤雌产雌松毛虫赤眼蜂生殖表型及适合度的影响

Effects of tetracycline on the reproductive phenotype and fitness of thelytokous Trichogramma dendrolimi Matsumura(Hymenoptera:Trichogrammatidae)

共生菌Wolbachia能够诱导许多节肢动物发生产雌孤雌生殖现象。由于该菌无法在宿主细胞外离体培养,人们常采用抗生素处理获得Wolbachia去除或滴度降低的宿主种群,用以研究Wolbachia对宿主的调控作用,但抗生素可能会对宿主产生附加效应。前人研究主要集中在抗生素处理是否可以恢复感染寄生蜂的两性生殖,较少关注抗生素对宿主适合度的影响。本研究利用不同浓度四环素(0、5 mg/mL、15 mg/mL和25 mg/mL)连续饲喂5代来明确四环素对产雌孤雌生殖的松毛虫赤眼蜂Trichogramma dendrolimi适合度的影响。研究结果如下:(1)随各浓度四环素处理世代的增加,雌蜂的繁殖力先降低后升高。在F 1代、F 2代和F 5代中,雌蜂繁殖力随四环素浓度的增加而显著下降,但在F 3代和F 4代中,抗生素浓度对雌蜂繁殖力无显著差异;(2)在四环素不同浓度处理下,F 1代和F 3代的羽化率与对照无显著差异,在F 2代、F 4代和F 5代中,四环素对羽化率存在负面影响;(3)经四环素处理的松毛虫赤眼蜂子代雄性比显著高于对照组。在5 mg/mL的四环素处理条件下,松毛虫赤眼蜂子代雄性比随处理世代的增加而升高,但在25 mg/mL的四环素处理条件下随世代的增加先升高后下降。结果表明:四环素能够使孤雌产雌松毛虫赤眼蜂恢复两性生殖,但对松毛虫赤眼蜂的适合度存在不利影响。此外,随着四环素处理世代的增加,松毛虫赤眼蜂对抗生素产生了一定的适应能力。

Endosymbionts Wolbachia are able to induce parthenogenesis in numerous arthropod species.Since they cannot be cultured in vitro,the common way of studying their effects on hosts is using antibiotic treatment to remove Wolbachia or reduce their titer in a host population.However,antibiotic treatment might bring side effects on hosts.Previous studies only focused on curing effect of an antibiotics to get Wolbachia-free bisexual host strains,and paid less attention to the side effects on host fitness.In this study,we used different concentrations of tetracycline(0,5 mg/mL,15 mg/mL and 25 mg/mL)for 5 consecutive generations to determine the side effects of tetracycline on the fitness of parthenogenetic Trichogramma dendrolimi infected with Wolbachia.The results were as follows:(1)as the generation of each concentration increased,the female fecundity significantly decreased at first,but then significantly increased.With higher concentrations,female fecundity significantly decreased in F 1,F 2,or F 5 generation,but showed no significant differences in F 3 or F 4 generation;(2)under different concentrations of tetracycline,the emergence rate in either F 1 or F 3 generation did not significantly differ from control group,while significantly negative effects of tetracycline were found in generation F 2,F 4 and F 5;(3)the male ratios of T.dendrolimi offspring in treatment groups were significantly higher than that in control group.Under 5 mg/mL tetracycline,male offspring ratio significantly increased over generations,whereas under the concentration of 25 mg/mL,it significantly increased and then decreased with higher generations.Our results indicated that:Tetracycline could force parthenogenetic T.dendrolimi to restore bisexual reproduction,but this antibiotic also inflicted negative effects on fitness of the latter;in addition,T.dendrolimi showed progressive adaptability to tetracycline with the increase of generation.