Cytochemical demonstration of acid Mucopolysaccharides in the epicuticular surface coat of the crab Carcinus maenas (L.) (Crustacea, Decapoda).

The epicuticle of marine decapod crustaceans is composed of three sublayers : the inner epicuticle, the cuticulin layer, and the surface coat which was previously described as an external layer rich in tannophilic proteins. Positive staining by ruthenium red and alcian blue suggests the presence in this layer of polyanionic sites and acid mucopolysaccharides. The surface coat might be viewed as a hydrophilic glycoproteinaceous layer reducing the surface tension between the hydrophobic cuticulin layer and the aqueous environment.