Origin and early development of female germ cells in Eoleptestheria ticinensis Balsamo-Crivelli, 1859 (Crustacea, Branchiopoda, Conchostraca)

We have studied the early stages of the development of the female germ cells in the Conchostraca Eoleptestheria ticinensis Balsamo-Crivelli, 1859. The gametes originate in a scattered way throughout the tubular units of the gonad, with no development gradient recognizable. The female germ cells arise from successive karyokineses not followed by cytokinesis, within an unorganised area in which a sort of plasmodium is formed. Each primordial nucleus of this germarium develops and then forms an individual plasmic membrane. Subsequently, the usual organules differentiate in the cytoplasm. The presence of synaptinemal complexes and the beginning of the endogenous vitellogenesis by the rough endoplasmic reticulum and the Golgi apparatus qualify the previtellogenesis. The general characteristics of this early development phase of the gametes, as well as several substantial differences in the gametogenesis with respect to the other Phyllopoda studied, lead us to suggest the systematic positioning of the Leptestheriidae.