Morphology of the alimentary canal of the gecko Hemidactylus mabouia (Moreau de Jonnès, 1818) (Squamata: Gekkonidae) / Morfologia do tubo digestivo da lagartixa Hemidactylus mabouia (Moreau de Jonnès, 1818) (Squamata: Gekkonidae).




Hemidactylus mabouia is the gecko species more thoroughly distributed in Brazil, being common in anthropic atmospheres, what turns easy its use as model for study of the reptiles. Likewise, aiming at to describe morphologically the alimentary canal of H. mabouia, 17 adult specimens were used, being collected fragments of the esophagus, of the oesophagogastric transition, of the stomach and of the small and large intestines, that were processed according to routine methods for anatomical, histological, histochemical and ultra-structural analyses. Histological sections were stained with Toluidine Blue or submitted to techniques for identification of glycoconjugates, proteins, alkaline phosphatase activity, mitochondria and argyrophil and argentaffin endocrine cells. The esophagus of H. mabouia is a tubular straight- lined organ, with the cranial portion more dilated, what favours the ingestion of whole preys and contributes to a rapid clearance of the bucco-pharyngeal cavity. The stomach has "J" form, with a long fundic region, which can be subdivided in oral fundic and aboral fundic, and a short pyloric region. The presence of macrophages in the gastric surface constitutes singular fact and reflects the defense need against invader microorganisms. As the one of the other carnivorous reptiles, the intestine of H. mabouia is short, being the small intestine more long and convoluted that the large intestine, that possesses a quite dilated colon followed for a short rectum. The oesophageal covering epithelium is pseudostratified with cells that secrete neutral and acid mucins; at the oesophagogastric transition there is a mixture of this epithelium with mucussecreting prismatic simple epithelium, whose cells secrete neutral mucins predominantly; in the stomach it is prismatic simple secreting neutral mucins; in the small intestine it is prismatic simple with absorptive cells and mucous cells secreting acid and neutral mucins; in the large intestine the absorptive cells are scarce, without brush border or with very short brush border, and the mucus-secreting cells are abundant. In the esophagus, the lamina propria is thin and aglandular; in the esophagus-gastric transition it becomes thick and filled by branched simple acinous glands, with mucous cells secreting neutral mucins and zymogenic cells producing of pepsinogen. Those multicellular glands were not observed in several reptiles, but they were described in many anuran amphibians, what can be related with the food habit of those animals. In the stomach, the oral fundic region presents long tubularacinous ramified simple glands, that become smaller, less ramified and more tubular in the aboral fundic region, and they are short tubular simple in the pyloric region. The fundic glands possess mucous cells secreting neutral mucins and oxynticopeptic cells, which differ of the oral fundic for aboral fundic in relation to the density of zymogen granules and mitochondria, indicating the existence of a secretion gradient of pepsinogen and hydrochloric acid. The pyloric glands just possess mucous cells secreting neutral mucins and argyrophil and argentaffin endocrine cells, which were also observed dispersed in the coating epithelium and in the glands of other segments of the alimentary canal, except in the esophagus. Surprisingly, argentaffin but non argyrophil cells were located in the oesophagogastric transition. In the intestine there are neither villi nor Lieberkühn crypts.


esophagus histochemistry microscopia eletrônica de varredura stomach large intestine intestino delgado scanning electron microscopy histoquímica estômago histologia small intestine esôfago biologia geral histology

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