Membranous tubular system in R-cells of decapod hepatopancreas investigated using electron-opaque tracers

Summary Ultrastructural studies of the hepatopancreatic R-cells of Palaemonetes zariquieyi revealed a basal tubular network. Tannic acid and lanthanum nitrate techniques established the presence of numerous infoldings of the basal and lateral plasma membranes that constitute the tubular system. Lipoprotein-like particles were detected inside this system. The contrast of these particles was increased by the osmium-thiocarbohydrazide-osmium (OTO) method. The ultrastructure of the membranous tubular system displays several morphological variants: (a) the tubular membranous system is curved and branched, with a regular reticular aspects, and is often associated with smooth endoplasmic reticulum (SER); (b) the basal and lateral plasma membranes exhibit shallow invaginations that are curved, and (c) the invaginations of the plasma membrane form a membranous branching system with a similar morphology to that of the SER. The possible intervention of the membranous tubular system in exchange processes with the haemolymph is discussed.