Ecdysis in the isopod Porcellio Scaber (Latreille).

Abstract

The outside layers of specimens of the isopod Porcellio scaber (Latreille) were examined at various times during the moult cycle, using transverse sections of the whole animal. Several structures associated with the cuticular layers were noted to alter over this period. The epidermal cells are active and vacuolated during the ecdysal phase but are inactive and at times non-vacuolated during that of the intermoult. The new epicuticle appears before the endocuticle and is apparent at least 21 hr prior to moulting. About 5 hr after moulting the new chitinous cuticle is differentiated into exocuticle and endocuticle; the deposition of these components of the cuticle being due to the progressive solidification of a secretion of the epidermal cells. By using the criteria set out in this paper, an individual's position in its moult cycle can be estimated.