Ultrastructure of the prezoeal cuticle and integument of the first zoea of Pagurus brachiomastus (Thallwitz) (Anomura,Paguridae) just after hatching

Transverse sections of the prezoea stage of Pagurus brachiomastus (Thallwitz) were made to determine the fine structure of the prezoeal cuticle and the exoskeleton of the first zoea, by using transmission electron microscopy. The thin cuticle covering the newly hatched prezoea is 15–17 nm thick, which is approximately 24 times thinner than the zoeal cuticle. High resolution revealed a trilaminar structure of the prezoeal cuticle, which is composed of an outer layer, approximately 4·4 nm thick, a mid lighter layer, approximately 3·5 nm thick, and an inner layer, approximately 7·7 nm thick. During the prezoeal stage, the inner zoeal exoskeleton consists of an epicuticle and an exocuticle, measuring approximately 0·36 μm thick. At this stage, there were no indications of the formation of endocuticle.