Abstract
Under drought stress, Phytoseiulus persimilis females are able to lay drought-resistant eggs through an adaptive maternal effect. The mechanisms making these eggs drought resistant still remain to be investigated. For this purpose, we studied the physiological differences between drought-resistant and drought-sensitive eggs. We compared the volume and the surface-area-to-volume ratio (SA:V) of the eggs, their sex ratio, their chemical composition (by gas chromatography-mass spectrometry), their internal and external structure [by scanning electron microscope (SEM) and transmission electron microscope (TEM) images], and their developmental time. Our results show that drought-resistant and drought-sensitive eggs have a different chemical composition: drought-resistant eggs contain more compatible solutes (free amino acids and sugar alcohols) and saturated hydrocarbons than drought-sensitive eggs. This difference may contribute to reducing water loss in drought-resistant eggs. Moreover, drought-resistant eggs are on average 8.4% larger in volume, and have a 2.4% smaller SA:V than drought-sensitive eggs. This larger volume and smaller SA:V, probably the result of a higher water content, may make drought-resistant eggs less vulnerable to water loss. We did not find any difference in sex ratio, internal or external structure nor developmental time between drought-resistant and drought-sensitive eggs. These results mark the first step in the understanding of the strategies and the energetic costs involved in the production of drought-resistant eggs in P. persimilis females.
Highlights
Parental care is a behavioral strategy through which parents increase the survival and growth of their offspring, often at a cost to their own survival and reproduction (Royle et al 2012)
We demonstrated that P. persimilis females start laying drought-resistant eggs when they are exposed to constant low relative humidity (RH) (65% RH) (Le Hesran et al 2019b)
Eggs laid by females exposed to constant low humidity had a bigger volume (4.8 × 10−3 ± 3 × 10−4 mm3) than eggs laid by females exposed to constant high humidity (4.4 × 10−3 ± 3 × 10−4 mm3)
Summary
Parental care is a behavioral strategy through which parents increase the survival and growth of their offspring, often at a cost to their own survival and reproduction (Royle et al 2012). In some spider and mite species, eggs are covered with silk layers or debris, to protect them against predators or stressful abiotic conditions (Marquardt et al 2016; Santos et al 2017). Besides these parental traits enhancing offspring fitness, parental care can benefit offspring through adaptive maternal effects (Benowitz et al 2015). Understanding the physiological adaptations involved in adaptive maternal effects is key to better estimate their consequences for offspring performance, as well as the costs of such maternal effects for the mothers, and the constraints to their evolution
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
