Quantification and ultrastructure of oosorption in Eretmocerus eremicus (Hymenoptera: Aphelinidae)

The potential for and ultrastructure of oosorption were examined in Eretmocerus eremicus, a short-lived whitefly parasitoid that obligately produces anhydropic oocytes. In the absence of hosts, median egg load decreased by approximately 12% per day between 2 days and 8 days following eclosion. Parasitoid mating status had no significant effect on either egg load alone or the relationship between egg load and age. Yolk degradation in E. eremicus is autolytic, with the enzymes required for yolk sphere digestion apparently being derived from within the ooplasm. The exochorion appear to be digested by the follicular epithelium concurrent with the uniform degradation of the entire ooplasm. The potential adaptive benefits of this novel oosorption mechanism to E. eremicus females include a reduction in the total digestion time per oocyte and resorption of chorion remnants. Finally, to our knowledge, the results of this study provide the first unequivocal ultrastructural evidence of a purely autolytic oosorption mechanism in Insecta.