Paiche (Arapaima gigas) belongs to the Kingdom Animalia, Phylum Chordata, Class Actinopterygii, Order Osteoglossiformes, Family Arapaimidae, Genus Arapaima, and its origin may date to the Jurassic period. The species has natural habitat in the Amazonian rivers, found mainly in marginal lakes, being considered an important fishing resource, with high market value and high demand for meat and leather in both Brazilian and international trade. This study aims to report the morphology of the esophagus and stomach by light microscopy and scanning electronics microscopy. The esophagus was presented as muscular, short, tubular and fan-shaped in the cranial portion, also presenting deep longitudinal folds, and the entire mucosa is covered by mucus secretory cells with distinct morphological characteristics. Pirarurcu’s stomach has a J-shape divided into three regions: cardiac with a lighter aspect, fundus portion with few folds in the mucosa, and pyloric with deeper folds, also presenting gastroliths in fundus and pyloric portions. Both microscopy studies highlighted three glandular regions, composed by mucoid columnar epithelial cells, gastric crypts with different shapes and sizes depending on each portion, in which the different shapes of the mucosal folds in each region of the stomach were evident, and digitiform microsaliences were found in the cardiac region, and micro-orifices and desmosome in the fundus region. Also, fundus and pyloric portions produce more mucus than the cardiac. Then morphology found was consistent with the eating habits and management of distinct characteristics of the digestive tract.
The study of the functional anatomy of the digestive system of fish, in particular the oropharyngeal cavity, is of great importance because it allows inferences about the feeding habit, mechanisms of capture, selection, and processing of food carried out by different species. Thus, the aim of this study was to describe the anatomical adaptations of the oropharyngeal cavity of the pirarucu (Arapaima gigas Schinz, 1822) using scanning electron microscopy (SEM) techniques. The oropharyngeal cavity of six specimens of pirarucu was collected in juvenile phase, from Aquaculture Research Center at the Universidade Federal de Rondônia (UNIR), created for commercial purposes. The anatomical pieces were fixed in 10% buffered formalin and processed for SEM analysis. Anatomically, the oropharyngeal cavity of the pirarucu is composed of five pairs of branchial arches, apical portion of the tongue, floor of the tongue, lower pharyngeal area, and upper pharyngeal plate. In SEM, we observed that the mucosa of the apex of the tongue and the upper pharyngeal roof have a smooth texture and are covered by squamous cells with numerous small openings scattered over the surface. The portions of the floor of the tongue and the lower pharyngeal area, on the other hand, have adaptations in the form of a projectile and numerous sensory papillae, giving a rough texture to the region. Thus, the oropharyngeal cavity of pirarucu is adapted for the capture, apprehension, and swallowing of its prey, with signs of carnivory.
Currently, the fish farming with Arapaima gigas has suffered from technological obstacles in the fields of reproduction, health and nutrition, making it necessary to know the morphology of its structures, so that it can advance in more technified research in scope of production in Rondônia state, as well as in aquaculture nutrition and health. Therefore, the aimed is to characterize the macro and microscopic morphology of posterior digestive system of A. gigas. The intestine of six specimens A. gigas in ideal slaughter size was analyzed. The analyzes were performed using light-sheet microscopy (LM) and scanning electron (SEM) techniques. The intestine basically showes similar histological characteristics in three analyzed portions (proximal, middle and distal). Same type of simple columnar epithelium with goblet cells was evidenced, with subtle variations in pattern of villi in each segment, and in number of goblet cells. In the rectum, the amount of goblet cells and evident longitudinal villi was expressive. Macroscopic anatomy and histology of the intestine A. gigas analyzed showes characteristics of adaptation to cultivation, according to their diet and habitat. The intestinal mucosa can divided into three distinct portions: proximal, middle and final intestine, in addition to the rectum and anus. In the pyloric cecum, the folds are slightly higher and poorly branched. The rectum, compared to the midgut, showed a higher occurrence of goblet cells in the mucosa. This increase in goblet cells observed in the posterior portion may related to the assimilation of ions and fluids that occur at this location.
Comparative Topographical Description of the Central Nervous System of the Macaw (Ara ararauna) and the Owl (Tyto furcata)Descripción Topográfica Comparativa del Sistema Nervioso Central del Guacamayo (Ara ararauna) y el Búho (Tyto furcata
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