Fine-grained secretory cells in the intestine of the lancelet,Branchiostoma (Amphioxus) lanceolatum,studied by light microscopy

Summary In the posterior part of the mid-gut epithelium in the lancelet, Branchiostoma lanceolatum, fine-grained cells occur. The appearance of the these cells is conspicuous with a basal and an apical swelling with small secretory granules. At the end of the secretion cycle the granular content is released into the gut lumen. The secretion product seems to consist of proteins and probably has an enzyme function. The restricted localization, the fine granulation, and the characteristic shape are features, that make these cells distinguishable from other secretory cells in the lancelet intestinal epithelium. A possible endocrine capacity of the cells is discussed.This work was supported by grant 2124-23 from the Swedish Natural Science Research Council and by grants from the Faculty of Science, University of Stockholm, Sweden.