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To study the gross and microscopic anatomy of the digestive system and adjoining organs (liver and pancreas) of Megaleporinus muyscorum, 25 adult specimens of both sexes, with a total length of 32.5 cm and 339 g, were euthanized. Serial 5 µm sections were obtained by paraffin technique and stained with hematoxylin-eosin. The mouth is relatively small in a subterminal position, with large flat teeth directed forwards, the gills are long, separated, and defined, the esophagus and stomach are short and muscular, and the latter is “V” shaped and low volumetric capacity. The pyloric ceca are digitiform and range between ten and 15, the intestine is relatively long, with little distention capacity and three convolutions. The liver is prominent, trilobed, and brownish, and the pancreas is diffuse. Histologically, the digestive system is composed of four layers: mucosa, submucosa, muscle, and serosa. The mucosa in the esophagus was made up of longitudinal folds and stratified flat epithelium with abundant goblet cells. The submucosa presented loose connective tissue in the three organs evaluated: the esophagus, stomach, and intestine. The muscular layer of the esophagus is made up of striated muscle with internal and external circular orientation, different from that reported for the stomach and intestine (smooth muscle with circular and longitudinal orientation). The structure of the digestive system of M. muyscorum is like that presented by other teleost, the position of the mouth and the teeth suggest that it has omnivorous feeding habits. [ABSTRACT FROM AUTHOR]

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Introduction: Ornamental Angel fish (Pterophyllum scalare) is one of the main commercialized species from South America, with an important number of national and international dealers. Objective: To make a histological and morphometric description of P. scalare digestive tract. Methods: Nineteen adult individuals were used. Intestinal coefficient values were obtained, and a macroscopic and microscopic description of esophagus, stomach, and intestine (anterior, middle and posterior) was carried out. Samples were processed for paraffin embedding, and 5 µm sections were stained with H&E and P.A.S. Positive P.A.S. cells were counted. Lumen area and tissue area were measured in representative digitalized sections from each region. Results: P. scalare exhibited a short esophagus, followed by a blind bag shaped, scarcely muscular stomach, and a short intestine (intestinal coefficient 1.66 +/- 0.52). Four constitutive tissue layers were identified: mucosa, submucosa, muscular and in some areas also a serosa layer. Esophagus exhibit abundant globet P.A.S. + cells and shows the larger tisular area was observed. Luminal area and perimeter are larger in anterior intestinal region. Conclusions: the intestinal coefficient value (1.66 +/- 0.52), and the histological and morphometric characteristics of the evaluated organs, suggest that P. scalare is omnivorous with soft prey preferences. [ABSTRACT FROM AUTHOR]

The study of feeding habits in fishes can give important information about their role in the fish community, their functional role in the ecosystem, and their relationships with all available resources. We studied H. sierraensis from Gaira River and performed eight bi-monthly samples between May 2014 and November 2015. We analyzed fish stomach contents by the numerical (% N), volume (% V) and frequency of occurrence (% FO) methods; we also calculated the index of food importance (IA), coefficient of emptiness (CV), trophic niche breadth (used H') and condition factor (K). Additionally, we determined the sex ratio, gonadosomatic index (RGS), fecundity, minimum and average size at sexual maturity, and oocyte diameter by standard methods. The Gaira River has irregular meanders with clear waters, and high current velocity through its drainage; it is generally oligotrophic, with a tendency to eutrophic condition in some places. Observed dissolved oxygen values were high (5.4 mg/L), electrical conductivity was 68.63 μS/cm, and pH was found neutral. We analyzed stomach contents of 477 specimens, and found a 1.59 % coefficient of vacuity. The species was found euryphagic in its feeding habits (H'= 0.69), omnivorous tending to insectivorous; its diet consisted mainly of Trichoptera larvae (Atanatolica sp.), followed in importance by snails (Gastropoda Pomacea sp.) and dipteran larvae such as Simulium sp. Significant differences in both frequency of occurrence and the volume consumed were observed for the different size classes, as well as between different seasons of the year. The condition factor indicated that the species was well fed. Sex was determined for 424 fish, of which 241 were male and 183 female, given a ratio of 1.3: 1 (male-female) which resulted significantly different (Chi 2: 16.14; p= 0.02). The gonadosomatic index indicated that reproduction occurs during the high water river phase, fecundity was high, and oocyte diameter was relatively small. Males reached sexual maturity at an average size of 67.08 mm SL, and females at 70.68 mm SL. Their life history strategy is seasonal r. Management and conservation plans for this species are required due to human intervention in their habitat, originated by the growing tourist activity in the area. [ABSTRACT FROM AUTHOR]