Differences in the permeability and function of eggshell in different-aged eggs of Frankliniella occidentalis (Thysanoptera: Thripidae)

Abstract

The western flower thrips Frankliniella occidentalis (Pergande) is an economically important invasive pest of crops in China. Previous work showed that the insecticide spirotetramat has lethal effects on Frankliniella occidentalis eggs, but that these effects decrease as the eggs age. It was hypothesized that the eggshell becomes less permeable to spirotetramat as the egg ages. Thus, the current study examined age-related changes in eggshell permeability by removing the eggshell using sodium hypochlorite solution. Eggs that were 0-h old ruptured, whereas 24-h-old eggs developed insoluble endoplasmic layers and embryonic development was normal. However, these eggs were more sensitive to spirotetramat treatment compared with control eggs, with only 11.67% of eggs surviving. Furthermore, when exposed to air, the rate of water loss from eggs reduced with age, with 0-h-old eggs shriveling within 10 min of exposure to air compared with 20 min for 24-h-old and 48-h-old eggs. Together, these results suggest that 0-h-old eggs have only thin eggshells, with poor water retention ability and weak resistance to chemicals; therefore, exposure of F. occidentalis eggs to insecticides should occur as early as possible during the egg-laying cycle. Thus, this study provides a basis for improving the biochemical control of F. occidentalis by using spirotetramat.