Histology of the hepatopancreas of the freshwater prawn Palaemonetes argentinus (Crustacea, Caridea).

The aim of this study is to describe the histological structure of the hepatopancreas of P. argentinus in intermoult stage in order to provide a baseline for future analysis of its modifications as indicator of environmental stress. Adults at sexual rest of both sexes were collected from Sotelo stream, tributary of Mar Chiquita lagoon, Argentina (38 degrees S 55 degrees W). P. argentinus hepatopancreas was studied by using histological techniques. The hepatopancreas is a bilaterally bilobed brown-yellowish organ. The structure is formed by a mass of blind tubules, with scarce intertubular space. Each tubule consists of a cylindrical epithelial layer surrounded by a basal lamina and myoepithelial cells. Four cellular types were recognized which represent E (embryonic), F (fibrillar), R (resorptive) and B (blisterlike) cells of other decapods. E-cells were found in mitosis and some F-cells had signs of cellular death. B-cells were observed in different phases of holocrine secretion and some groups of desquamated cells appeared at medial and proximal zones, revealing an important cellular turnover rate. According to these observations F, R and B cells are differentiated independently from E-cells.