Morphological and Histochemical Characterization of the Mucosa of the Digestive Tract in Engraulis anchoita (Hubbs and Marini, 1935)

Abstract

The histomorphological aspects as well as the histochemical content and distribution of glycoproteins (GPs) in the mucosa of the digestive tract of the anchovy Engraulis anchoita were studied. The buccopharyngeal cavity is lined by a squamous stratified epithelium with mucous superficial cells; the oesophagus shows two zones, cranial with a squamous stratified epithelium with mucous superficial cells and caudal with a columnar secretory epithelium. Finally, the stomach presents both the cranial and pyloric portion lined with a simple columnar epithelium. Tubular branched glands, formed by a single type of glandular cell, located along the stomach, are more numerous in the cranial portion. The GPs were identified with (1) oxidizable vicinal diols; (2) sialic acids and some of their chain variants, C7 or C9; (3) sialic acid residues with O-acyl substitution at C7 or C8; (4) carboxyl groups and (5) sulphate groups. Histochemical tests showed that the buccopharyngeal cavity presented the largest amount of the different types of mucosubstances. Epithelial secretory cells were found in the oesophagus, which synthesized a large quantity of sialosulphoglycoproteins likely to be related to a protective role. The surface epithelium of the stomach synthesizes and secretes acid and neutral GPs, probably related to the movement of fluids and to the absorption of easily digested substrates, respectively. Although great differences exist between different species, in E. anchoita as in other fish species, the wall of the digestive tract is composed of the four layers classically described for vertebrates. The GPs secreted by the epithelial cells are suggested to be important for the protection and inhibition of microorganisms. In addition, they are involved in enzymatic digestion of food, absorptive functions and lubrication of the alimentary tract.

Histologia e caracterização histoquímica do tubo gastrintestinal de Pimelodus maculatus (Pimelodidae, Siluriformes) no reservatório de Funil, Rio de Janeiro, Brasil

“…O esôfago é curto e, como na maioria dos peixes estudados, contém todas as camadas características de um órgão tubular do sistema digestório dos vertebrados: camada mucosa, submucosa, muscular e uma serosa (GODINHO, 1967;GODINHO et al, 1970;GARRIDO et al, 1993;TIBBETS, 1997;ALBRECHT et al, 2001;DIAZ et al, 2003). A túnica mucosa caracterizou-se pela presença de pregas longitudinais menos proeminentes do que aquelas encontradas em peixes marinhos como Engraulis anchoita Hubbs & Marini, 1935(DIAZ et al, 2003, um provável efeito da diferenciação na dieta destas espécies, com esta última sendo filtradora planctófaga.…”

“…Apesar das diferenças interespecíficas no trato gastrintestinal, semelhanças estruturais básicas são comuns dentro do grupo (DIAZ et al, 2003). Em algumas espécies as diferenças estão proximamente relacionadas com a natureza do hábito alimentar, tamanho do corpo e sexo (KAPOOR et al, 1975;SMITH, 1989).…”

<b>Morphological and anatomical characterization of the digestive tract of Centropomus parallelus and <i>Centropomus undecimalis</i></b> - doi: 10.4025/actascibiolsci.v35i4.14352

“…In current study it was impossible to confirm the existence of these regions as well as a widelydeveloped muscular coat in the pyloric region, which facilitates the expulsion of gastric emptying and food to the foregut. According to Stroband and Van der Veen (1981), the main functions of the stomach are the storage of food and defense against microorganisms for the production of hydrochloric acid which initiates digestion process within the stomach (GARTNER; HIATT, 2007). The mucus of the stomach covered with simple epithelium was composed of cylindrical tubular gastric glands in the lamina propria.…”

“…According to Gartner and Hiatt (2007), the absorptive cells showed numerous microvilli where several enzymes were secreted. These cells acted in the process of the absorption of lipids, amino acids and carbohydrates.…”

“…The apical surface of epithelial cells in three regions of the stomach showed a strong reaction to PAS, indicating the place of secretion of neutral mucopolysaccharides in the epithelium, for the protection of the mucosal surface. According to Diaz et al (2003), the mucopolysaccharides secreted by the epithelial cells seemed to be important for the protection of the organ wall and for the inhibition of the action of microorganisms, also involved in enzymatic digestion of food. The neutral mucopolysaccharides, found in current study, may have a protective effect against high mucosal acidity of stomach contents.…”