Functional morphology of the digestive tract epithelium in Phoronis vancouverensis (Pixell): An ultrastructural and histochemical study
✍ Scribed by John H. Vandermeulen
- Publisher
- John Wiley and Sons
- Year
- 1970
- Tongue
- English
- Volume
- 130
- Category
- Article
- ISSN
- 0362-2525
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✦ Synopsis
The ultrastructure of the gut regions of the marine filter-fceder Phoroais vancouvrrensis was correlated with enzyme activity as revealed histochemically. The oesophagus, proventriculus, and stomach epithelia showed intense csterase and acid and alkaline phosphatase aclivity. The ataining reaction was contined primarily to small globulcs in the apical cytoplasm of the epithelial cells. Elcctron micrographs of the samc regions showed a high incidence of zymogenlike granules, with a corresponding abundance of ribosomes and of rough endoplasmic reticulum. Also, the proventricular and to a lesser cxtent the stomach epithelia were found to contain a large number of lipid bodies. This was confirmed with positive Sudan 11' staining for fats.
The intestinal region of the gut was found devoid of csterase and phosphatase activity. The epithelial surface in this region was found elaborated into microvilli. The entire gut is ciliated. A new paired-cilium apparatus is described in this phylum.
From these findings Phoronis vancouvercnsis is concluded to he suitably adapted to its continuous filter-feeding exislencc, with the anterior gut epithelia synthesizing hydrolytic enzymes for relcase into the lumina of the proventriculus and stomach. Subsequently, in the hindgul the products of initial extra-cellular digestion are absorbed via the microvilli and treated intracellularly within the intestinal epithelium. The proventriculus is further thought to function in lipid absorption and storage. The presencc of chromaffin-like granules obscrved in some proventricular and intcstinal epithclial cells suggests that digestion i n this phylum may in part be under ncurosecretory control