Ultrastructure of the proboscidial papillae in some Glycera species (Annelida: Polychaeta: Glyceridae)

Abstract

The ultrastructure of the proboscidial papillae in five species of Glycera: G. alba, G. lapidum, G. tesselata, G. tridactyla, and G. unicornis is described based on transmission electron microscopy. The papillae are composed of four to five cells: one anterior mucous cell, one posterior serous cell and two to three multiciliated primary sensory cells which are presumed to be mechanoreceptors. The intracellular ciliary rootlets of the sensory cells are striated filamentous structures which might serve as skeletal elements. In two species (G. lapidum and G. tesselata) papillae sometimes bear lateral groups of cilia in addition to the cilia located apically. The physiological role of the papillae is discussed.