Ultrastructural study of yolk formation in Porcellio scaber Latr. (Isopoda).

Two types of yolk are formed in the developing oocytes of a terrestrial crustacean, Porcellio scaber. The intra-oocytic yolk, arises through autosynthesis, and the extra-oocytic yolk, is derived from micropinocytosis. the so-called disc shaped bodies, which occur in large numbers within the cisternae of a branched system of endoplasmic reticulum, are precursors of the intra-oocytic uolk. Dictyosomes are not involved in yolk formation in this species. Thus, the vitellogenesis of Porcellio scaber occurs in a manner analogues to that described in the aquatic crustaceans, which indicates that environmental factors have relatively little effect on this process.