MOLTING IN A PARASITIC NEMATODE, PHOCANEMA DECIPIENS: I. CYTOLOGICAL EVENTS

Abstract

The structure of the cuticles of the last-stage larva and of the adults of Phocanema decipiens, as well as the deposition of the adult cuticle, has been examined by light microscopy. The larval cuticle consists of a single layer of longitudinal fibers resting on a basal lamella, a matrix composed of two faintly osmiophilic bands lying in a less osmiophilic medium, and an inner and an outer cortical layer. The adult cuticle is produced by the hypodermis and arises as three successive waves of condensation at the outer edge of the hypodermis, resulting in a three-layered structure. The middle of these three layers later splits into three osmiophilic bands lying in a less osmiophilic matrix. Ecdysis occurs as soon as the second layer is complete, and the new cuticle continues to grow in thickness after the old cuticle has been shed. The secretion of the new cuticle is accompanied by enlargement of the nuclei, nucleoli, and mitochondria of the hypodermis. The muscle cells appear to secrete material into the hypodermis.