Fine structure of the epithelium of the gut in the crayfish (Procambarus clarkii) with special reference to the cytoplasmic microtubules.

The epithelial cells of the midgut and hindgut in the crayfish were studied by electron microscopy. The epithelial cells of the midgut are characterized by formation of cytoplasmic tubules or lamellae in the basal half of the cells. These structures appear to be specified infoldings of lateral plasma membranes, and are assumed to be similar in terms of structure and function to the cytoplasmic tubular structures in the chloride cell of fish gill filaments. In the hindgut, the epithelial cells are prominently provided with cytoplasmic microtubules. Thick bundles of them are attached to both luminal and basal plasma membranes. When attached with microtubules, the basal plasma membrane of the epithelial cells usually makes an epithelio-myonal junction with that of the processes of striated muscle fibers derived from the muscular coat, in a manner similar to that of the intercalated disc of the cardiac muscles.