Histoarchitectural features of the hepatopancreas of the Amazon River prawn Macrobrachium amazonicum / Histoarquitectura del hepatopáncreas del camarón de la Amazonia Macrobrachium amazonicum

In decapod crustaceans, the digestive gland is concerned with the digestion, absorption of nutrients, the storage of reserves and excretion. The metabolism and the histological and histochemical changes of the hepatopancreas are observed in response to physiological demands as moult, reproduction, digestive process. Thus the hepatopancreas structure should be recognized to provide important morphological information to future studies involving the nutrition requirements of freshwater prawn culture. In this study, second-generation Macrobrachium amazonicum produced from wild broodstock collected in the state of Para in Brazil were used. Thirty adult male and female M. amazonicum were selected and randomly transferred to five experimental units for macroscopic and microscopic studies. The hepatopancreas of M. amazonicum is a large, yellowish-brown, compact organ, which occupies much of the cephalothoracic cavity. It has right and left halves that are enclosed together in a laminar connective tissue capsule, and at the same time they are separated by an interstitial connective tissue. The two halves are thereby called the right and left hepatopancreatic lobes. The principal tubule gives rise to four secondary tubules at each hepatopancreatic lobe. The morphological and functional unit consists of a blind-ended hepatopancreatic tubule, considered in the present study as the hepatopancreatic lobule. Each hepatopancreatic tubule can be subdivided into distal, medial and proximal zones. The hepatopancreatic tubule is lined by a pseudostratified epithelium that consists of five different cell types, which include the E-cell (embryonic), F-cell (fibrillar), B-cell (blister-like), R-cell (resorptive) and M-cell (midgut or basal). It is important to emphasize that the function of each cell type in the hepatopancreas during the digestive cycle is not yet established for decapods.

La glándula digestiva en los crustáceos decápodos asume las funciones de digestión, absorción de nutrientes, almacenamiento de las reservas energéticas y excreción de metabolitos. El metabolismo y las alteraciones histológicas e histoquímicas son observados como respuesta a necesidades fisiológicas, tales como: muda, reproducción y procesos digestivos. Por lo tanto, se requiere conocer la estructura histológica del hepatopancreas con el fin de reunir información morfológica para futuros estudios que consideren las necesidades nutricionales para el cultivo de los camarones de agua dulce. Fueran utilizados 30 animales, machos y hembras de Macrobrachium amazonicum, producidos a partir de reproductores colectados en el Estado de Para, Brasil. Las observaciones macro y microscópicas permitieron concluir que el hepatopancreas del M. amazonicum es un órgano grande y compacto de color amarillo tendiendo a marrón, que ocupa la mayor parte de la cavidad céfalo-torácica. El órgano presenta dos mitades, derecha y izquierda, las cuales están envueltas por una cápsula de tejido conjuntivo, y al mismo tiempo, separadas por tejido conectivo intersticial. Las dos mitades del órgano son identificadas como lobos derecho e izquierdo. Cada lobo presenta un túbulo principal que origina cuatro túbulos secundarios. Por lo tanto, la unidad morfofuncional del hepatopancreas consiste en un túbulo hepatopancreático de fondo ciego, considerado en esta investigación como lóbulo hepatopancreático. Cada lóbulo hepatopancreático puede ser dividido en 3 regiones: distal, media y proximal, y en su totalidad, se observa revestido por epitelio seudo estratificado que reúne cinco tipos celulares: célula E (embrionaria), célula F (fibrilar), célula B (globosa), célula R (reabsortiva) y célula M (basal). Es importante enfatizar que la función de cada tipo celular del hepatopancreas no está todavía aclarada para los decápodos.

Fine structural analysis of the epithelial cells in the hepatopancreas of Palaemonetes argentinus (Crustacea, Decapoda, Caridea) in intermoult

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