Origin and formation of eggshell in Limnadia lenticularis (Linnaeus, 1761), Crustacea, Branchiopoda, Conchostraca

We studied the structure of the walls of the central gonadal duct in Limnad ia lenticularis, the structures responsible for eggshell formation. The lon gitudinal duct wall is made of a single layer of somatic glandular cells, m ixed with female germ cells. The material forming up the shell was produced within a system of vesicles derived from the nuclear membrane and then tra nsported to the lumen's surface and released in the form of drop-like secre tions that came together gradually in a mass that would eventually fill the gonad. We then studied eggshell maturation in newly spawned and mature egg s and observed it through its various transformations until they reached th eir definitive shape, that of so-called "twisted" eggs. We compared data on ultrastructure, obtained from comparison of the eggshell in Limnadia with those from other Branchiopods as Triops and the Leptestheriidae, and from t he results we concluded that eggshell resistance in the Branchiopods we obs erved is correlated to the species reproductive strategies.