Calcitonin-like cells in the pharynx of the ascidian Styela clava.

A small group of granulated endocrine cells have been described in the endostylar region of the pharynx in Styela. These cells are argyrophilic and exhibit calcitonin-like immunofluorescence. Tests with antisera to other peptides all proved negative. Cells from animals exposed to elevated calcium levels showed a degree od degranulation. The possibility that these cells may represent ancestral ultimobranchial "C" cells is discussed.