Histochemical research of enzymes involved in cellular digestion in the digestive tract of tub gurnard, Chelidonichthys lucerna.

Abstract

The tub gurnard Chelidonichthys lucerna (Linnaeus, 1758), Triglidae, is an opportunistic, demersal carnivorous fish. Data on the digestive enzymes of tub gurnard have not been reported in the literature. Therefore, the aim of this research was to investigate the distribution and intensity of alkaline phosphatase, acid phosphatase, non-specific esterase, and aminopeptidase in the digestive tract of tub gurnard. To investigate data about those enzymes tissue samples of the esophagus, anterior and posterior part of the stomach, pyloric caeca, anterior, middle and posterior part of the intestine proper, and rectum were taken. Azo-coupling methods were used to detect the enzymatic reactions. The intensities of the reactions were measured using ImageJ software. Alkaline phosphatase, acid phosphatase, and non-specific esterase activities were found in all parts of the digestive tract. The brush border of the pyloric caeca and intestine proper were the main sites of alkaline phosphatase reaction, with intensity decreasing toward the posterior parts of the digestive tract. The high intensities of acid phosphatase were found in the epithelium of the anterior part of the stomach, pyloric caeca, anterior part of the intestine proper, and in the rectum. The intensity of non-specific esterase was mainly increased from the anterior to the posterior parts of the digestive tract. Aminopeptidase activity was found in the esophagus, pyloric caeca, and intestine proper. Our results suggest that the entire digestive tract of the tub gurnard is involved in the digestion and absorption of dietary components.