The Structure and Mineralization of the Carapace of the Crab (Cancer pagurus L.) 3. The epicuticle

Decalcified and undecalcified preparations of the crab Cancer pagurus in the intermoult condition were studied to examine the mineralization and structure of the epicuticle, using light microscopic, electron microscopic, and microradiographic methods. The epicuticle was found to be composed of two layers, one superficial membrane, and one thicker layer, measuring 1‐2 μm. From the base layer spines or microtrichia projected. These were approximately 18 μm long and built like the remainder of the epicuticle. The spines and the base layer of the epicuticle contained vertical canals which in undecalcified sections accomodated columns of crystals. These canals were the only location in which minerals occurred in the epicuticle. In decalcified preparations filamentous strands were observed in the canals. Elsewhere in the epicuticular tissue no fibrillar structure was observed. The canals and their contents seemed to extend across the junctional zone between the epicuticle and the exocuticle.