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deMeloGermano,R.,Stabille,S.R.,deBrittoMari,R.,Pereira,J.N.B.,Faglioni, J.R.S. and de Miranda Neto, M.H. 2014. Morphologicalcharacteristics 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 Pterodorasgranulosus. Therefore, macro-, meso-andmicroscopicaspectsof15 P. granulosusDTs were analysed. The muscular layer was composed of striated skeletal mus-cle in the oesophagus and smooth muscle i n the other segments. The epitheliumprogressed from a stratified pavement in the oesophagus to a simple column inthe other segments, with a flat striated border in the intestine. A large number ofmucus-secreting periodic acid-Schiff (PAS)-positive cells were observed in theoesophagus. In the stomach, the number of glands in the region decreasedtowards the cardiac–fundic region, and none were found in the pylorus. Theintestine showed an epithelium with absorptioncellsandanincreasingnumberof PAS-positive caliciform cells towards the distal region. Tests showed that theoesophagus is adapted for passing and preparing food for the chemical digestionthat occurs in the stomach, which also has storage functions without grindingaction. The proximal intestinal region was consistent with fat absorption, andthe medium region, with the absorption of other nutrients. The distal region wasshort and consistent with a role in absorption for osmoregulation as well as inthe formation, storage and disposal of faeces.Ricardode Melo Germano, Departamento de Ci^enciasMorfologicas, Universid-ade Estadual de Maringa, Av. Colombo, no. 5790 –Bloco H79 –CEP. 87020-900, Maringa –Parana, Brasil. E-mail: prof.ricardogermano@gmail.comIntroductionThroughout the evolutionary process, fish have developedtheir own mechanisms to obtain food and to survive, with spe-cific physiological and morphological changes of the digestivesystem associated with their feeding behaviour (Dzhumaliyev1982; Fanta et al. 2001).In general, the digestive tubes of fish present the classicstratigraphic organisation that is described for the tubularorgans of other vertebrates. However, the macro- and micro-scopic structures of the segments are indicative of the fairlyprecise nature of the fish diet and how food is ingested by thespecies (Chaves and Vazzoler 1984; Seixas-Filho et al. 2000;Fugi et al. 2001). These factors have led to the appearance ofmorphological changes from the oesophagus to the distalintestine, which can be used to distinguish fish structures fromclassical descriptions.Pterodoras granulosus, described by Valenciennes in 1821(Fowler 1951) and popularly known as ‘armado’, ‘armadocomum’ or ‘abotoado’, belongs to the Siluriformes order,Doradidae Family and is found in the basins of the Paran a,Paraguay, Uruguay, Amazonas and Goias rivers. This specieswasnotfoundintheupperParana River and its floodingchannels until the construction of the Itaipu reservoir andwater levelling, when the P. granulosus increased its distribu-tion (Agostinho et al. 2003; Feitoza et al. 2004).