Freeze-fracture and deep-etched view of the cuticle of Caenorhabditis elegans.

At ultrastructural level, the Caenorhabditis elegans (C. elegans) cuticle shows the presence of well-defined layers, one of them is a membrane-like structure designated as epicuticle, always present on the outermost surface of nematodes. Freeze-fracture replicas revealed the existance of two faces of the epicuticle: a inner face containing numerous particles, and a almost smooth outer face. Deep etching replicas confirmed the existance of these two faces of the epicuticle showing in some replicas two particle populations on the outer face of L4 and adult forms of C. elegans. Also a previously unrecognized structure was noted in the cuticle of C. elegans, a matrix composed by network of globular and filamentous structures, leaving in between them spaces, which probably are occupied by water in the living adult and L4 larvae specimen. This network demonstrates either a compact nature or loose nature according to their cuticle location. Deep etching replicas of the adults nematode revealed large spaces between the cortical and basal layers which are regularly interrupted by struts connecting each other by fibers in a particular arrangement.