Light and Scanning Electron Microscope Examination of the Digestive Tract in Peppered Moray Eel, Gymnothorax pictus (Elopomorpha)

Abstract

The morphology of the digestive tract of the peppered moray eel, Gymnothorax pictus (G. pictus) (Elopomorpha: Anguilliformes) was examined using both light and scanning electron microscopy. The digestive tract is composed of the esophagus, the stomach, and the intestines; pyloric caeca were absent. The stomach was divided into a cardiac region that was continuous with the esophagus, a body which terminated in a long blind sac, and a pyloric region that was continuous with the intestine. The short intestine possessed several partitions that were created by the mucosal folds within the posterior region. The terminal region of the stomach was characterized by the thick longitudinal muscularis and subserosa, and the gastric glands and microvilli were absent. Ciliary tufts of ciliated cells were observed on the surface of the partition-like mucosal folds within the intestinal wall. Acidic mucus was secreted throughout the digestive tract. It was suggested that the terminal region of the stomach is specialized for storage of large food items. In addition, it is possible that the partition-like mucosal folds within the intestine perform a function similar to that of the spiral valve and, and along with ciliated cells, facilitated digestion and absorption. The acidic mucus likely maintained surface epithelium pH and protease activity. Within a phylogenetic context, the absence of a pyloric caeca in G. pictus while possessing an intestine implies that this species is affiliated to groups that had branched off earlier than basal teleosts. Anat Rec, 296:443-451, 2013. V C 2013 Wiley Periodicals, Inc.

Ultrastructure of the digestive tract in neotropical carnivorous catfish Hemisorubim platyrhynchos (Valenciennes, 1840) (Siluriformes, Pimelodidae)

“…Folds with different orientations were observed in the luminal surface of the fundic region, which probably enable the distension of the stomach during ingestion of large prey and also increase the surface area for digestive activity (Sinha and Chakrabarti, ; Namulawa et al ., ). The gastric surface of H. platyrhynchos presents polyhedron‐shaped cells, similar to those observed in other teleosts such as Anguilla anguilla that has a pentagonal mosaic pattern (Clarke and Witcomb, ), Salmo gairdneri that has square, pentagon, or hexagon cells (Ezeasor and Stokoe, ), Gymnothorax pictus (Takiue and Akiyoshi, ) and Lates niloticus (Namulawa et al ., ) that has polygon‐shaped cells. Moreover, the surface of epithelial cells of the studied species shows secretion granules.…”

“…These granules are secreted into the gastric lumen by exocytosis (Noaillac‐Depeyre and Gas, ; Ostos‐Garrido et al ., ) and they protect the epithelium of stomach from autodigestion processes caused by secretions produced in the gastric glands (Ferraris et al ., ). Other authors found microvilli related to absorption in the gastric epithelial cells in some teleosts, such as Salmo gairdneri (Ezeasor and Stokoe, ), Mystus aor (Sinha and Chakrabarti, ), Gymnothorax pictus (Takiue and Akiyoshi, ). However, the surface of stomach of H. platyrhynchos has no microvilli, which highlights the primary function of the stomach in food digestion.…”

Histological and Scanning Electron Microscopic Examination of the Digestive Tract in Whitespotted Conger, Conger Myriaster (Anguilliformes)

“…The digestive tract in Elopomorpha is characteristic of that in teleosts; some possess both a stomach and the pyloric caeca [5], while basal teleosts in Elopomorpha have a large blind sac stomach only with no pyloric caeca [6][7][8]. In the Elopomorpha, the stomach in Anguilloidei is histologically divided into the cardiac, fundus, and pyloric regions [9,10], and in Gymnothoraxpictus [Muraenoidei], the stomach forms the characteristic terminal region within the blind sac stomach [8]. The terminal region of the stomach is characterized by thick longitudinal muscularis and subserosa layers, and gastric glands are absent.…”

Mucin in epithelial cells in oesophagus and stomach of black tetra, Gymnocorymbus ternetzi (Characidae, Teleostei)

“…a somewhat younger order, has been shown to mostly contain both acidic and neutral glycoproteins (Garrido et al 1993;Díaz et al 2003;Santos et al 2007). Recently, peppered moray eel (Gymnotharax pictus) from the order Anguilliformes has been shown to display acidic mucin in stomach (Takiue et al 2013). However, in some species from the order Perciformes, the mucin in the stomach surface epithelial layer seems to be mainly neutral (Hernandez et al 2001;Carrassón et al 2006).…”