ULTRASTRUCTURE OF ALIMENTARY EPITHELIA OF LOBSTERS, HOMARUS-AMERICANUS AND HOMARUS-GAMMARUS, AND CRAB, CANCER MAGISTER

The ultrastructure of the alimentary tract lining, excluding the hepatopancreas, of lobsters, Homarus americanus and H. gammarus, and Dungeness crab, Cancer magister, was investigated with transmission electron microscopy. The foregut lining consists of a cuboidal epithelium with extensive interdigitations of the lateral cell membranes and adhering junctions. The ultrastructural organization of the midgut and midgut caeca resembles that of other transporting epithelia. The cells possess a microvillous border, and the basal cytoplasm contains numerous mitochondria and an anastomosing system of smooth endoplasmic reticulum. Hemocytes, presumed neurosecretory axons, and putative endocrine cells occur within the epithelium of the midgut and midgut caeca. Hindgut epithelial cells have numerous mitochondria in the apical cytoplasm, and their basal cell membranes are elaborately infolded. These observations suggest that one of the principal functions of the midgut, midgut caeca, and hindgut epithelia is the transport of ions and water. © 1979 Springer-Verlag.