ABSTRACT
The present work describes the effect of different salinities on the functional morphology of the P. argentinus hepatopancreas and analyses the tissue recovery after re-acclimation to freshwater. Adult prawns of both sexes at sexual rest were collected from a tributary of the Mar Chiquita coastal lagoon. The prawns were acclimated in aquaria to four salinity conditions: 0 (control), 8, 16 and 24. To evaluate the possible tissular recovery, after 60 days individuals from all the treatments were gradually acclimated to freshwater and maintained for other 30 days. Hepatopancreas samples were processed at the beginning of the trial and every 30 days using standard histological techniques for OM and TEM. The individuals from all the treatments, except the controls, showed a continuous weight decrease, and survival was lower when higher the salinity. At 30 days from the beginning of the experiment, hepatopancreas from 16 and 24 salinities showed an enlarged tubular lumen and an infolded basal lamina. Ultratructurally, nuclear retraction, cytoplasmolysis, and RER membranes separated with electron-dense content were observed in all the treatments except 0. After 60 days, profound alterations were observed with the three treatments. After the re-acclimation period, there was no reestablishment of the functional cytology. The tolerance to short-term salinity changes explains the capability of this prawn to inhabit in estuarine environments.
ABSTRACT
The aim of this study is to describe the ultrastructure of the hepatopancreas of P argentinus in intermoult. P argentinus hepatopancreas was studied using standard TEM techniques. Each tubule consists of four cellular types: E (embryonic), F (fibrillar), R (resorptive) and B (blister like). E-cells have embryonic features and some of them were found in mitosis. F, R and B cells possess an apical brush border. F-cells have a central or basal nucleus, a conspicuous RER, and dilated Golgi cisternae. R cells show a polar organization of organelles in three areas: apical, with numerous mitochondria and sER tubules, a central are a with the nucleus and RER, and a basal area containing a sER-like tubule system and mitochondria. B-cells were observed at different stages of their life cycle. In an early differentiation stage they comprise an apical endocytotic complex and Golgi vesicles. The fusion of endocytotic and Golgi vesicles originates subapical vacuoles. During maturation, a big central vacuole is formed by coalescence of subapical vacuoles. The central vacuole is eliminated by holocrine secretion. The ultrastructure suggests that F-cells synthesize proteins, R-cells storage nutrients and B-cells have a secretory or excretory function, and confirms the independent origin of F, B and R cells from the embryonic cells
Subject(s)
Adult , Animals , Crustacea , Environmental Pollution , Epithelial Cells , Epithelium , Hepatopancreas/anatomy & histology , ShellfishABSTRACT
The present work describes the histological changes in the hepatopancreas of Palaemonetes argentinus during the moulting cycle. The hepatopancreas of individuals at different moult stages were dissected and studied using histological techniques. The hepatopancreas in intermoult presents four typical cell types (E, F, R and B) and follows the general plan of the rest of decapods. During early premoult (D1), there is an important secretory activity and many R-cells have several subapical vacuoles and are highly columnar. In early postmoult (A), B-cells are confined to the proximal zone of the tubules. Some of the tubules show a folded basal lamina in late premoult and postmoult. Degenerative desquamation occurs at the proximal zone of the tubules in all the stages, this zone being replenished by mitosis of E cells. Mucopolysaccharides and glycogen reserves are more abundant in premoult than in the rest of the cycle. Cellular height increased in premoult and decreased towards the intermoult, stage of more stability. R-cells are the most abundant, and F-cells do not change significantly through the cycle. The observations suggest that the hepatopancreas of P. argentinus undergoes a significant dynamic and cellular turn over rate in relation to moult.
Subject(s)
Animals , Male , Female , Decapoda , Molting , Decapoda , Digestive System , Glycogen/analysis , Glycosaminoglycans , MicrovilliABSTRACT
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.