Fig. 5

Ultrastructure of clamp I. a The central part of two anterior jaw sclerites connected by an anterior joining sclerite and the posterior part of a median plate sclerite. The nerve fibres are located at the base of the anterior joining sclerite. b Terminal part of both jaws forming the clamp, i.e. the part coming in direct contact with host tissue (gills). c A cross-section of the clamp musculature, with hemidesmosomes connected to the lateral sclerite; note also the electron-dense material (arrows) adherent sclerite surface. d A detail of the sclerite surrounded by radial muscle fibers with clearly visible hemidesmosomes. e A detail of the posterior median plate sclerite; note the glandular cell with secretory vesicles and a nucleus with nucleolus in the cytoplasm at the basal area of the sclerite. Secretory vesicles are spread throughout the syncytial layer cytoplasm. f A detail of the anterior jaw sclerite, showing the large nerve plexus proximally to the external syncytial layer and the well-developed musculature, enabling clamp movement. Abbreviations: AJ, anterior jaw sclerites; AJS, anterior joining sclerite; BL, basal lamina; GC, glandular cell; Hd, hemidesmosomes; Lu, luminal part of the clamp; MF, muscle fibers; N, nucleus; Neo, Neodermis; Nu, nucleolus; NP, nerve fiber; PMP, posterior part of median plate; Sc, sclerite; SL, sclerite lumen