engleski

Histological characteristics of the posterior part of digestive tract in small-spotted catshark (Scyliorhinus canicula)

The posterior part of the digestive tract in the small-spotted catshark (Scyliorhinus canicula) consists of the foregut (esophagus and stomach), midgut (intestine) and hindgut (rectum). The aim of this study was to investigate the histological characteristics of the posterior part of the digestive tract in the small-spotted catshark. For this purpose, tissue samples of the esophagus, cardiac and pyloric parts of the stomach, proximal intestine, spiral intestine and rectum were taken from four small-spotted catsharks. The tissue samples were fixed in 10% neutral buffered formalin, embedded in paraffin and sectioned with microtome into 6 µm sections. The sections were stained using five different methods: hematoxylin and eosin, Mallory trichrome, Verhöeff-Van Gieson, Alcian blue-PAS kit and the seven-reagent kit for determining reticulin fibers. The general structure of the investigated parts was studied by an Olympus BX41 microscope. From interior to exterior, the wall of the digestive tract was composed of mucosa, submucosa, muscularis and serosa. The mucosa of the esophagus and rectum was lined by stratified cuboidal to columnar epithelium with projections on the apical part of the cells. Cardiac and pyloric parts of the stomach as well as proximal and spiral intestine were lined by simple epithelium with microvilli. Mucous cells were present in all investigated parts of the digestive tract except in the stomach. Lamina propria was composed predominately of connective tissue. In the cardiac part of the stomach, abundant gastric glands were present. Muscular lamina was identified in all parts except in the rectum. Submucosa was identified in all parts except in the rectum where it was blended with the lamina propria. Muscularis was composed of inner, circular and outer longitudinal layers of smooth muscle. Two exceptions were found. The outer muscular layer of the esophagus was composed of striated muscle while the spiral intestine mostly had just the circular layer. Serosa was composed of connective tissue with simple squamous epithelium. Further investigation will be focused on histochemical research to define enzyme activities of the posterior part of digestive tract in the small-spotted catshark.

small-spotted catshark ; digestive tract ; histology

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