Epithelial cytology and function in the digestive gland of Thenus orientalis (Decapoda: Scyllaridae)

Abstract

The morphology and epithelial cytology of the digestive gland of the slipper lobster Thenus orientalis is described. The primary ducts possess extensive musculature which indicate that they may move fluid into and out of the glands. Immunohistochemical localization of trypsin demonstrated that it is synthesized and secreted solely by the F-cells in the digestive gland. Trypsin is absent from tissue in the oral region, proventriculus, and hindgut, but is present in digestive fluid throughout the alimentary tract, indicating that it has a role in extracellular digestion. Substantial accumulations of lipid in the cytoplasm of R-cells indicate a role in the absorption and storage of digestion products. Residual bodies in the apical cytoplasm are consistent with metal-storing granular inclusions and supranuclear vacuoles in the R-cells of other decapods. Based on the presence of an apical complex of pinocytotic vesicles and subapical vacuoles, an absorptive role for B-cells is evident. The presence of trypsin in the central vacuole is consistent with a digestive role, although our results cannot distinguish whether the enzyme is endogenous (lysosomal versus digestive) or was absorbed from the tubule lumen for excretion.