Fine structural survey of old cuticle degradation during pre-ecdysis in two European Atlantic crabs.

Light and transmission electron microscopy were used to monitor changes due to the degradation of the old exoskeleton and related events in the sclerites, articular membranes, and gills of two decapod crustaceans (Carcinus maenas and Macropipus puber) during pre-ecdysis. In both sclerites and articular membranes, degradation follows a similar general pattern in both crab species, while the gill cuticle appears unaltered. In early pre-ecdysis (D(0)), the degradation of the old cuticle starts with the secretion of ecdysial droplets by the epidermis.