Anatomical and ultrastructural study of the pharyngeal bulb in Protodrilus (Polychaeta, Archiannelida) II. The stomodeal and its cuticle.
The epidermal and stomodeal cuticles of Protodrilus are described then compared. The thin epidermal cuticle, the thickness of which is about the same over all the body, is characterized  both by the absence of fibrils in its deepest part and by the extension of epidermal microvilli above the cuticle. The stomodeal cuticle, the thickness of which is as variable as that of the epithelium, presents two layers of fibrils comparable to the collagen fibrils described in the cuticle of other Annelida, as well as a relatively diversified supramicrovillous coating. The anterior cuticular thickening or grating plate, is characterized by the length of the epithelial microvilli, the thickness of the cuticular matrix and the superficial cuticular zone with supramicrovillous denticles supported by an axis of fibrous bundles. In the stomodeal cuticle, the fibrillar material seems to give to the cuticle best resistance to deformation during the pharyngeal bulb contraction, while an especially elaborated supramicrovillous coating is found in regions most exposed to friction. These features contrast with the relative simplicity of the epidermal cuticle.
D000818:Animals; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D004817:Epidermis / Q000648:ultrastructure; D004848:Epithelium / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000648:ultrastructure; D007365:Intercellular Junctions / Q000648:ultrastructure; D008247:Lysosomes / Q000648:ultrastructure; D008928:Mitochondria / Q000648:ultrastructure; D009940:Organoids / Q000648:ultrastructure; D010614:Pharynx / Q000648:ultrastructure; D011077:Polychaeta / Q000648:ultrastructure*