Adhesive papillae ofAscidia malacaswimming larvae: investigations on their sensory function

Summary Swimming larvae of Ascidia malaca bear, in the anterior region of cephalenteron, three adhesive papillae through which they can attach to a substratum prior to metamorphosis. The ultrastructural investigations described in the present work have mainly revealed the presence of three cell types constituting the papillae: (a) collocytes, (b) axial columnar cells, (c) sensory cells. Collocytes, whose ultrastructure is typical of secretory cells, form the adhesive secretion. The ultrastructural observations of the axial columnar cells are insufficient to explain their function. Probably this cell type plays a supporting role though some sensory function cannot be excluded due to the pres…