Egg-shells in mites. Vitelline envelope and chorion in a water mite, Limnochares aquatica L. (Acari, Limnocharidae)



Results of ultrastructural investigations (SEM and TEM) of the formation and structure of eggshells in the water mite, Limnochares aquatica, are presented. The material of the vitelline envelope is secreted in two stages by the oocyte commencing vitellogenesis. The vitelline envelope is later transformed into endochorion and during the passage through the reproductive tract it becomes covered with exochorion, produced by the female reproductive accessory gland. The exochorion swells in water to acquire a foamy structure.