Some Aspects of Cuticular Organization of the Branchiopod, Streptocephalus dichotomus

ABSTRACT The structural features of the cuticle of Streptocephalus are described. The epicuticle and endocuticle, unlike those of other Crustacea, stain alike and show similar chemical characters (apart from the absence of chitin in the epicuticle). This feature appears to be related to the absence of tanning of the cuticle, which remains soft and colourless in all stages of growth. In the epicuticle the outermost very thin layer, whose presence can be inferred from chemical tests, seems to correspond to the outer epicuticle of Crustacea, but this layer lacks histological distinctness. The protein constituent of the cuticle is unlike that of other arthropod cuticles so far studied. It differs markedly from arthropodin or sclerotin and recalls collagen. The significance of the peculiarities of the cuticle is discussed. It is suggested that the structure and chemical characteristics of the cuticle may indicate that it represents a generalized and unspecialized condition of the arthropod cuticle.