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The family Potamotrygonidae are the only species of stingrays restricted to fresh water and located exclusively in South America. The objective of this research was to analyze the morphological aspects and germ cells of the male reproductive tract of Potamotrygon amandae. The samples were fixed in 10% formalin, and then dehydrated in an ascending ethanol series (70 to 100%). To carry out light microscopy analyses, they were embedded in paraffin, cut and stained; as for scanning electron microscopy analyses, the samples were dried, glued in metallic bases and metalized. The gross morphology consisted of the following paired organs: testis, epididymis, deferent duct, Leydig gland, seminal vesicle, clasper, and the clasper gland. Microscopically, several stages of spermatogenesis were observed in the testis, occurring in spherical follicles, similar to other stingrays. The epididymis was formed by one duct subdivided in various tubules. The deferent ducts were continuous with the epididymis, and the lumen was full of spermatozoa. The Leydig glands consisted of glandular units with eosinophilic content in the lumen of some, and the deferent ducts ran parallel to the ventral portion. The seminal vesicles possessed numerous compartments to store the sperm, with a wall similar to a hive, and the lumen was full of spermatozoa. Alcian Blue (AB) and Periodic Schiff-Acid (PAS) performed in the Leydig Gland, deferens ducts and seminal vesicle was positive only in the connective tissue, the cilia were PAS+ and the nuclei stained weakly for AB. The clasper gland was composed of unit glands and was covered with striated muscle externally. It stained very well with Periodic Schiff-Acid. The morphological aspects of the male reproductive tract of Potamotrygon amandae were similar to other stingrays. [ABSTRACT FROM AUTHOR]

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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. [ABSTRACT FROM AUTHOR]