Abstract The purpose of this study was to describe the structure of the midgut (hepatopancreas and intestine) in the endemic species, Macrobrachium carcinus. Thirty specimens were collected, and the midgut was fixed in Bouin's solution for histological and histochemical analyzes by light microscopy. The hepatopancreas consists of two lobes that connect to the end of the stomach by primary ducts, which originate secondary tubules or hepatopancreatic ducts, that branch into hepatopancreatic tubules. The hepatopancreatic duct presents a columnar epithelium composed of R- and F- cells with evident brush borders for absorption and storage. The hepatopancreatic tubule is lined by epithelium with five cell types (E, F, R, B, and M). The distal region presents all cell types, with a predominance of E-cells that correspond to epithelial renewal. The middle region presents F- and B- cells, characteristic of extracellular and intracellular digestion. The proximal region, with B- and R- cells, performs the final digestion, storage, and extrusion of the cells with waste material. The intestine is lined by a single cell type with an evident brush border, suggesting luminal absorption. This cellular arrangement along the length of the midgut proposes distinct morpho-functional characteristics of digestion, absorption, and storage in this species.

O estresse é um dos maiores obstáculos na criação de rãs e pode ser causado por fatores como sistemas de criação inapropriados; manejos inadequados bem como outras situações. O objetivo do presente estudo foi avaliar o hemograma, eritrograma e o leucograma da rã-touro (L. catesbeianus) quando expostas ao estresse de diferentes manejos: adensamento e manipulação desenvolvidos no laboratório e repetidos no campo para as devidas comparações em um período experimental de 30 dias. O experimento de densidade foi conduzido com quatro tratamentos: 70 animais m-2 (D70); 100 animais m-2 (D100), Controle; 150 animais m-2 (D150) e 200 animais m-2 (D200) com respectivos 10, 14, 21 e 28 animais/caixa no laboratório. Cada tratamento foi realizado com três réplicas simultâneas. O experimento de triagem foi conduzido com três tratamentos: Tratamento Sem Triagem (ST); Tratamento com Triagem Parcial (TP) a cada 15 dias e Tratamento com Triagem Total (TT) a cada 15 dias. Cada tratamento foi realizado com quatro réplicas simultâneas. A metodologia das análises de sangue seguiu as recomendações internacionais. No presente estudo pode-se observar que os animais experimentados em campo não refletiram a mesma resposta de estresse observada no laboratório nos dois experimentos, o que conferiu a plasticidade destes animais.

Stress is one of the major obstacles in frog culture and can be caused by factors such as inappropriate farming systems; inadequate management among other situations. The objective of the present study was to assess the hemogram, erythrogram and leukogram of bullfrogs (L. catesbeianus) when exposed to stress caused by different types of management: density and handling (manipulation), developed in the laboratory and repeated in the field for the appropriate comparisons in a experimental period of 30 days. The density experiment was conducted with four treatments: 70 animals m-2 (D70); 100 animals m-2 (D100), Control; 150 animals m-2 (D150) and 200 animals m-2 (D200), with 10, 14, 21 and 28 animals/box in the laboratory, respectively. Each treatment was performed with three simultaneous replicates. The handling experiment was conducted with three treatments: Treatment Without Handling (WH); Treatment with Partial Handling (PH) every 15 days and Treatment with Total Handling (TH) every 15 days. Each treatment was performed with four simultaneous replications. The methodology of the blood analysis followed international recommendations. In the present study we could observe that the animals of the field experiment did not reflect the same stress response observed in the laboratory in both experiment, which demonstrated the plasticity of these animals.

The aim of this study was to characterize the normal structure of the liver of Hemisorubim platyrhynchos, a carnivorous freshwater catfish found in Neotropical region, using gross anatomy, histology and histochemistry. Anatomically, the liver presents C-shaped and only two lobes: smaller right and bigger left. The gallbladder is located in right lobe and shows elongated shaped. Histological analysis demonstrated that the hepatic parenchyma is made of two hepatocytes plates surrounded by sinusoids. The hepatocytes are polygonal-shaped cells, with spherical nucleus and a dark prominent nucleolus. The cytoplasm presents large amount of lipids and glycogen deposits PAS positives. There are no hepatic lobules or portal triads. Bile ducts are lined by columnar epithelial cells with apical mucosubstances PAS and AB positive. Furthermore, the liver presents melano-macrophages centers, distributed next to the blood vessels and bile ducts, constituted by cells accumulating pigments, whose presence may be related to the nutritional status of the fish. Moreover pancreatic tissue was observed in visceral portion of liver, formed by exocrine pancreatic tissue and islet organ, constituting an extrahepatic pancreas.

El objetivo de este estudio fue caracterizar la estructura normal del hígado de Hemisorubim platyrhynchos, un bagre carnívoro de agua dulce encontrado en la región neotropical, utilizando anatomía macroscópica, histología e histoquímica de mucosustancias. Anatómicamente, el hígado presenta una forma de C y sólo dos lóbulos de tamaño diferente: menor derecho y mayor izquierdo. La vesícula biliar se encuentra en el lóbulo derecho y presenta forma alargada. El análisis histológico demostró que el parénquima hepático está hecho de dos placas de hepatocitos rodeados por sinusoides. Los hepatocitos son células poligonales con núcleo esférico y un nucléolo oscuro prominente. El citoplasma presenta gran cantidad de lípidos y depósitos de glucógeno PAS positivos. No hay lóbulos hepáticos o triadas portal. Los conductos biliares están revestidos por células columnares epiteliales con mucosustancias apicales PAS y AB positivos. Además, el hígado presenta centros de melanomacrófagos, distribuidos junto a los vasos sanguíneos y conductos biliares, constituidos por células que acumulan pigmentos, cuya presencia puede estar relacionada con el estado nutricional de los peces. Por otra parte, el tejido pancreático se observó en la porción visceral de hígado, formado por tejido pancreático exocrino y órgano islote, que constituye un páncreas extrahepático.

The aim of the present study was to analyze the ultrastructural aspects of spermatogenesis in Phalloceros caudimaculatus, during cell proliferation. The parenchyma is organized morphologically as lobular restricted spermatogonial testis. Spermiogenesis in this species is characterized by four morphological stages of development (spermatids S1 through S4). The mature spermatids and spermatozoa heads are situated at the periphery of the cyst surrounded by the cytoplasm of the Sertoli cells. The germ cell's ultrastructure and spermatogenesis in P. caudimaculatus are very similar to that of other poeciliids.

El objetivo del presente estudio fue analizar los aspectos ultraestructurales de la espermatogénesis en Phalloceros caudimaculatus, durante el periodo de proliferación celular. El parénquima testicular está morfológicamente organizado como lobular espermatogonial restricto. La espermiogénesis en esta especie se caracteriza por cuatro etapas morfológicas de desarrollo (espermátidas S1 hasta S4). Las cabezas de las espermátidas maduras y espermatozoides están situadas en la periferia de los cistos, rodeados por el citoplasma de las células de Sertoli. La ultraestructura de las células germinativas y la espermatogénesis en P. caudimaculatus son muy similares a las de otros poecílideos.