The principal cell types of the trunk epidermis of Phoronis psammophila are categorized and described on the basis of their ultrastructural and histochemical properties. There are seven cell types: uniciliated supporting cells with a well-developed microvillar layer, fine-granule-containing cells with distinctive finger-like processes that contain vesicles and extend into the microvillar layer, and five types of generalized gland cells distinguished mainly by the fine structure of their secretory granules. Gland cells lack cilia but possess intact basal body complexes within the cytoplasm in close association with the Golgi complex. This is an unusual feature for gland cells, and suggests that they may have recently evolved from more typical ciliated epithelial cells. The secretory product of the gland cells contains either acidic mucopolysaccharides, which are mostly sulfated, or neutral mucopolysaccharides and protein. The possible functions of these cell types are discussed. The supporting cells are presumably involved in direct uptake of nutrients and (or) the protection and cleaning of the epidermis. The fine-granule-containing cells may help the animal adhere to the tube, whereas the gland cells probably function in the secretion of the tube.
S3c1-5 Two-photon functional imaging of neurons and secretory gland cells(S3-c1: "Imaging Science for Biophysics",Symposia,Abstract,Meeting Program of EABS & BSJ 2006)