The ultrastructural evaluation of digestive cells in the hepatopancreas of the Amazon River prawn,Macrobrachium amazonicum

Abstract

The Amazon River prawn Macrobrachium amazonicum is endemic to tropical South America and is being intensively exploited by artisanal fisheries in Brazil. Limited information is available about the nutritional requirements of M. amazonicum, although the production of this species is now technically feasible. The digestive process in this species is still unclear and investigation into the digestive cells of its hepatopancreatic epithelium is required. Thus, the hepatopancreas from 15 specimens were fixed in Karnovsky Solution and processed for Transmission Electron Microscopy. Our results indicate that E cells are located at the distal portion of the hepatopancreatic tubule and are involved in mitotic activity. The cylindrical R cells are sparse and are only found in the proximal portion of the hepatopancreatic tubule. According to its ultrastructural characteristics, this cell is involved in pinocytosis. M cells are generally found near the R cells. The F cells are scattered throughout the length of the hepatopancreatic tubules, and B cells are observed mainly in the proximal and middle regions. F cells and B cells are likely related to, respectively, the synthesis of enzymes and the intracelular digestion. R-and M cells are probably related to material storage. Thus, these findings provide basic information on the cell types that perform protein digestion in M. amazonicum, and will be useful in further nutritional research. The identification and characterization of digestive cells is an important step towards understanding the digestive mechanisms.

Effects of dietary cholesterol on hepatopancreas associated with morphotypic differentiation in male Amazon River Prawns,Macrobrachium amazonicum(Heller, 1862)

“…Furthermore, Simon () and Cervellione et al () proposed that a prolonged supply of high levels of essential nutrients impairs the balance of digestive processes in the hepatopancreas of crustaceans due to a structure disorganisation and morphometric changes of the hepatopancreatic tubules. In this sense, M. amazonicum diets with 0.5% and 1.0% addition of cholesterol maintained the morphological characteristics of the digestive process described for the species (Franceschini‐Vicentini et al, ; Ribeiro et al, ). However, 2.0% addition of cholesterol causes changes in the morphological characteristics of F‐ and B‐cells.…”

“…B‐cells are frequent in M. amazonicum hepatopancreatic epithelium and present a large basal vacuole and some apical vesicles (Franceschini‐Vicentini et al, ; Ribeiro et al, ). In this study, the levels of vacuolization of B‐cells enhanced as the percentage of cholesterol increased, and these vacuoles could suggest different functional stages of this cell type (Ribeiro et al, ).…”

“…B‐cells are frequent in M. amazonicum hepatopancreatic epithelium and present a large basal vacuole and some apical vesicles (Franceschini‐Vicentini et al, ; Ribeiro et al, ). In this study, the levels of vacuolization of B‐cells enhanced as the percentage of cholesterol increased, and these vacuoles could suggest different functional stages of this cell type (Ribeiro et al, ). Furthermore, the high availability of essential nutrients for crustaceans, such as cholesterol, interferes with B‐cell endocytosis (Ahearn, Grover, & Dunn, ; Chen et al, ), possibly resulting in the hypervacuolization of this cell type in the 2.0% cholesterol treatment.…”

“…This cell type was found sparse in the epithelium 0% and 0.5% treatments, and it was not evidenced in treatments with 1.0% and 2.0% cholesterol. According to the literature, R‐cells are related to the stock of materials absorbed from the lumen and mobilized from B‐cells (Ribeiro et al, ; Zilli et al, ). Considering that B‐cells are hypertrophied and hypervacuolized, and probably the mobilization of nutrients to hemolymph is impaired, R‐cells presented a decreased demand for compounds storage.…”

“…In crustaceans, the hepatopancreas is the organ responsible for digestion, as well as the assimilation and storage of important compounds involved in several metabolic processes (Felgenhauer, ; Gibson & Barker, ; Rőszer, ). This organ takes up most of the cephalothorax of crustaceans and consists of a network of tubules that presents an epithelium with five cell types, E‐, R‐, F‐, B‐ and M‐ cells, which promotes the digestion, assimilation and storage of nutrients (Franceschini‐Vicentini et al, ; Ribeiro, Papa, Vicentini, & Franceschini‐Vicentini, ; Vogt, Storch, Quinitio, & Pascual, ).…”