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

Abstract

Histochemical properties of the mucus cells in oesophagus and stomach in a teleost, black tetra (Gymnocorymbus ternetzi), are described and compared. These cells were sac-shaped, very numerous, and embraced by ordinary epithelial cells with highly variable shape, throughout the entire length of oesophagus. The stomach luminal epithelial cells were filled with mucin apically, whereas the gastric gland cells lacked mucin. When treated with alcian blue (pH 2.5) before periodic acid-Schiff, the oesophagus mucin displayed a colour between blue and magenta, whereas it was strongly magenta in stomach. After high iron diamine followed by alcian blue (pH 2.5), the oesophagus mucin displayed a clean blue colour, whereas the stomach mucin was uncoloured. The present results for the lectin affinities in mucus cells in oesophagus of black tetra were similar to those of stomach and together suggest that these mucins contain significant amounts of Nacetylglucosamines, galactose-N-acetylgalactosamines sequences, and probably some sialic acid in terminal positions attached to the N-acetylglucosamine, but the mucin seems nearly or entirely to lack glucose and mannose. In addition, all its N-acetylgalactosamines in oesophagus, unlike in stomach, seem to be attached to galactose, as these amines were not coloured by DBA in oesophagus, but intensely coloured by PNA. Together the present results suggest that the oesophagus mucin in black tetra contains both neutral and carboxylated glycoproteins, but lacks sulphated glycoproteins, whereas the stomach mucin contains neutral glycoproteins only. The present results for black tetra suggest that the large amounts of oesophageal mucus and its increased toughness caused by anions may largely compensate for the lack of salivary glands. The stomach mucin lacks anions, a feature which may enhance the flow of the mucus and therefore also its ability to clean and protect the stomach wall against the gastric juice.

The Neuroendocrine Regulation of Food Intake in Fish: A Review of Current Knowledge

“…Diet and feeding habits is reflected in the anatomy and physiology of the gastrointestinal tract. For example, carnivores or omnivores (such as most Characiformes and Siluriformes) have stomachs, pyloric caeca, and relatively short and straight intestines, whereas herbivores or detrivores (e.g., Cypriniformes and Cyprinodontiformes) may lack both stomach and caeca and have long and convoluted intestines (Leknes, 2015). Different diets and guts translate into different digestive enzyme profiles and different methods of nutrient storage (Day et al, 2011), as seen for lipids (e.g., in muscle in “oily” fish such as salmon and herring vs. liver in “lean” fish such as cod and flatfish), which usage might also be affected by reproductive stages and modes (guarding vs. non guarding; mature vs. immature; oviparous vs. viviparous).…”

Central regulation of food intake in fish: an evolutionary perspective

“…(10) Gadiformes: Atlantic cod (Gadus morhua), burbot (Lota lota). both stomach and caeca and have long intestines (Leknes 2015). Different diets and GIT also translate into different digestive enzyme profiles and different methods of nutrient storage (Day et al 2011).…”

The digestive tube of Piaractus brachypomus: gross morphology, histology/histochemistry of the mucosal layer and the effects of parasitism by Neoechinorhynchus sp.

“…This result was similar to what was reported for two species of Anguilliformes (Domeneghini et al, ; Takiue & Akiyoshi, ). Gastric mucus that is rich in neutral glycoproteins has characteristics that enable it to clean and protect the walls of the stomach against enzymatic action of pepsin and the hydrochloric acid present in gastric juice (Leknes, ). Acid glycoproteins in acid mucus suppress the degradation of mucus by proteases and bacteria (Neuhaus et al, ).…”

“…Production of such substances is associated with increased secreted mucus viscosity and with protection against the various pathogenic agents than can come into contact with the oesophagus through swallowed food (Abidi & Parwez, 2015;Ferraris et al, 1987). Neutral mucins help in lubrication and, when predominant in the oesophagus, indicate pre-gastric digestion (Cao & Wang, 2009 that is rich in neutral glycoproteins has characteristics that enable it to clean and protect the walls of the stomach against enzymatic action of pepsin and the hydrochloric acid present in gastric juice (Leknes, 2015). Acid glycoproteins in acid mucus suppress the degradation of mucus by proteases and bacteria (Neuhaus et al, 2007).…”