A histological study of the seminal vesicle of the armoured catfish Corydoras aeneus.

Most species of Corydoras exhibited a reproductive behaviour called 'T-position', and exhibited an accessory gland in the male genital tract, called the seminal vesicle. It appeared that both the structure and the composition of the fluid varied considerably between the species investigated. Consequently, different opinions were proposed regarding the possible role of seminal vesicle on this particular reproductive behaviour. Male adults of Corydoras aeneus were collected, anaesthetized, and samples of seminal vesicle were fixed in Bouin's solution. The sections were stained with haematoxylin-eosin and periodic acid Schiff. The seminal vesicle showed a system of anastomosed secretory tubules, forming a vesicular collective network, which gave rise to the vesicular ducts. The latter fused with the testicular efferent ducts and formed the spermatic ducts. Considering this fusion, when the sperm cells reached the spermatic ducts, the fluid produced at the seminal vesicle covered them. Histochemical studies evidenced the presence of neutral and acid glycosaminoglycans in the seminal fluid. Considering the reproductive behaviour of C. aeneus, it is believed that the protection associated with the immobilization of the sperm cells assures the sperm integrity during the passage through female's intestine until fertilization.

Morphological Study of the Liver in the Teleost Oreochromis niloticus / Estudio Morfológico del Hígado en el Teleósteo Oreochromis niloticus

Liver samples of Oreochromis niloticus cultivated in floating net cages were fixed for histological and ultrastructural studies with the objective of describing the hepatic parenchymal structure and the intrahepatic exocrine pancreatic tissue. Anatomically, the liver showed only two hepatic lobes. Histological analysis demonstrated that the hepatocytes were spread out as anastomotic cords, arranged in two cellular layers and surrounded by sinusoids. The intrahepatic exocrine pancreatic tissue exhibited an acinar arrangement and was diffused in the hepatic parenchyma. Structural analysis showed that the hepatocytes had a rounded nucleus and a rough endoplasmic reticulum with a parallel disposition to the nuclear membrane. The exocrine pancreatic cells showed secretion granules at the apical portion and the rough endoplasmic reticulum was concentrically distributed.

Con el objetivo de describir la estructura del parénquima hepático y del páncreas exocrino intrahepático del Oreochromis niloticus, fueron fijados para estudios histológicos y ultraestructurales fragmentos de hígado de peces cultivados en jaulas flotantes. Se evidenciaron sólo 2 lóbubos hepáticos. El análisis histológico demostró que los hepatocitos se encontraban organizados en forma de cordones anastomosados, dispuestos en dos capas celulares y cercados por sinusoides. El tejido pancreático exocrino intrahepático se encontró difuso en el parénquima hepático y se destacó por su organización acinar. El análisis ultraestructural demostró que los hepatocitos presentaban núcleos redondos y el retículo endoplasmático rugoso estaba dispuesto paralelamente a la membrana nuclear. Las células pancreáticas exocrinas presentaban gránulos de secreción localizados en la porción apical y el retículo endoplasmático rugoso estaba organizado de manera concéntrica.

Testicular ultrastructure and morphology of the seminal pathway in Prochilodus scrofa.

The seminiferous tubules of Prochilodus scrofa present a coiled morphological arrangement with intertubular anastomoses and unrestricted spermatogonial distribution. The structural pattern of the seminiferous tubules is cystic, with cysts formed by cytoplasmic prolongations of Sertoli cells. Inside the cysts are observed different types of germ cells. The seminiferous tubules open individually on the ventral surface of the main testicular duct present in each testis. Each main testicular duct prolongs as a spermatic duct, fusing with the spermatic duct of the opposite side to form the common spermatic duct which opens into the urogenital papilla. The mature sperm cysts break and extravasate their content into the lumen of the seminiferous tubules from which the seminal fluid and the spermatozoa penetrate the main testicular duct, the spermatic duct and the common spermatic duct for semen ejaculation.