F. Scanabissi et C. Mondini, Origin and formation of eggshell in Limnadia lenticularis (Linnaeus, 1761), Crustacea, Branchiopoda, Conchostraca, INVERTEBR R, 37(1), 2000, pp. 1-9
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.