Morphological characteristics of the Pterodoras granulosus digestive tube (Valenciennes, 1821) (Osteichthyes, Doradidae)

Abstract

de Melo Germano, R., Stabille, S.R., de Britto Mari, R., Pereira, J.N.B., Faglioni, J.R.S. and de Miranda Neto, M.H. 2014. Morphological characteristics of the Pterodoras granulosus digestive tube (Valenciennes, 1821) (Osteichthyes, Doradidae). -Acta Zoologica (Stockholm) 95: 166-175.Little is known about the digestive tube (DT) morphology of the fish Pterodoras granulosus. Therefore, macro-, meso-and microscopic aspects of 15 P. granulosus DTs were analysed. The muscular layer was composed of striated skeletal muscle in the oesophagus and smooth muscle in the other segments. The epithelium progressed from a stratified pavement in the oesophagus to a simple column in the other segments, with a flat striated border in the intestine. A large number of mucus-secreting periodic acid-Schiff (PAS)-positive cells were observed in the oesophagus. In the stomach, the number of glands in the region decreased towards the cardiac-fundic region, and none were found in the pylorus. The intestine showed an epithelium with absorption cells and an increasing number of PAS-positive caliciform cells towards the distal region. Tests showed that the oesophagus is adapted for passing and preparing food for the chemical digestion that occurs in the stomach, which also has storage functions without grinding action. The proximal intestinal region was consistent with fat absorption, and the medium region, with the absorption of other nutrients. The distal region was short and consistent with a role in absorption for osmoregulation as well as in the formation, storage and disposal of faeces.Ricardode Melo Germano, Departamento de Ciências Morfol ogicas, Universidade Estadual de Maring a, Av. Colombo, nº. 5790 -Bloco H79 -CEP. 87020-900, Maring a -Paran a, Brasil.

Morphological characteristics of the digestive tract of Schizodon knerii (Steindachner, 1875), (Characiformes: Anostomidae): An anatomical, histological and histochemical study

“…Morphological studies of the digestive tract of fish are considered effective tools for understanding the mechanisms of ingestion, digestion and absorption of food, and have recently been carried out for several species (Xiong et al 2011, Germano et al 2013, Løkka et al 2013. The digestive system of fish show distinctive morphological and functional diversity (Diaz et al 2003), due to the high biodiversity in teleost fish and the different positions they occupy in the food chain (Santos et al 2007).…”

“…However, they present a wall consisting of four layers: mucosa, submucosa, muscularis and serosa (Albrecht et al 2001, Xiong et al 2011, Wilson and Castro 2011. Studies of those layers have indicated that the main differences occur in the epithelium and are related to the feeding habits (Albrecht et al 2001), type of food ingested (Germano et al 2013), absorption and production of mucosubstances (Albrecht et al 2001, Santos et al 2007). …”

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

“…In a species from the order Beloniformes, this mucin has been reported to be composed mainly of sialomucin, but also some sulphomucin (Tibbetts 1997). Pedini et al (2001) reported that the oesophagus mucus cells in Umbrina cirrosa (Perciformes) contain mainly acidic glycoproteins, whereas Germano et al (2014) found that the oesophagus mucus cells in Pterodoras granulosus (Siluriformes) contain mainly neutral mucin. Recently, it has been found that the oesophagus mucin in freshwater tubenose goby (Proterorhinus semilunaris) from the order Perciformes usually contains both neutral and acidic glycoproteins (Wolczuk et al 2014).…”

“…The oesophagus in carnivorous fish is adapted for passing and preparing large food particles for the chemical digestion that occurs in the stomach (Germano et al 2014). The high number of such cells in this tube in teleosts may reflect the fact that fish lack salivary glands and that the mucus may play similar lubrication roles in oesophagus as the saliva mucus in higher vertebrates.…”

“…The present knowledge indicates that the amount and detailed composition and carbohydrate pattern of mucus in the various parts of the digestive tract in fishes seem to vary much from species to species, and to be mainly determined by the diet and feeding habits, less so with the evolutionary relationships or how they evolved (e.g. recent studies by Carrassón et al 2006;Santos et al 2007;Díaz et al 2008a, b;Jaroszewska et al 2008;Banan Khojasteh et al 2009;Hernandez et al 2009;Cao and Wang 2009;Redondo and Alvarez-Pellitero 2010;Cao et al 2011;Leknes 2011;Germano et al 2014;Faccioli et al 2014). Most of the studies mentioned above have been performed on species from evolutionary young teleost orders like Pleuronectiformes and Perciformes, but also some species from old orders like Clupeiformes, Siluriformes, Cypriniformes, and Characiformes have been examined.…”