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

Abstract

Summary We studied the structure of the walls of the central gonadal duct in Limnadia lenticularis, the structures responsible for eggshell formation. The longitudinal duct wall is made of a single layer of somatic glandular cells, mixed with female germ cells. The material forming up the shell was produced within a system of vesicles derived from the nuclear membrane and then transported to the lumen's surface and released in the form of drop-like secretions that came together gradually in a mass that would eventually fill the gonad. We then studied eggshell maturation in newly spawned and mature eggs and observed it through its various transformations until they reached their 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 the results we concluded that eggshell resistance in the Branchiopods we observed is correlated to the species reproductive strategies.