Fig. 3

Musculature of Pycnophyes kielensis; anterior with introvert everted. Micrographs obtained with a confocal laser scanning microscope of one kinorhynch with introvert fully everted. The musculature was stained with Alexa-488-labeled phalloidin and appears green. a is an average projection, b–g are single scans from the average projection shown in a from ventral to dorsal. Numbers indicate segment number, the animal is oriented with the anterior end upwards, the scale bar is valid for all micrographs and represents 75 µm. a Average projection overlay over a transmission micrograph to show the position of the muscles within the cuticle. b Ventral most view with placid retractors and primary spinoscalid musculature. c Slightly more dorsal view than b with pharyngeal bulb retractors. d Slightly more dorsal view than c with pharyngeal bulb protractors, gut musculature and mouth cone muscles. e Slightly more dorsal view than d with pharyngeal bulb protractors inserting at the same position as the dorsoventral muscles in segment 1. f Slightly more dorsal view than e with dorsal longitudinal muscles. g Slightly more dorsal view than f with y-shaped muscles on the dorsal side and DAPI staining of the brain in blue. h Maximum projection of the trunk of another specimen showing the insertion points of the pharyngeal bulb retractors in segments 4, 5, and 6. br brain, dlm dorsal longitudinal muscle, dvm dorsoventral muscle, gm gut musculature, llm lateral longitudinal muscles, mcm mouth cone muscle, mcr mouth cone ring muscle, pb pharyngeal bulb, pbr pharyngeal bulb retractor, plr placid retractor, pp pharyngeal bulb protractor, ysm y-shaped muscle, vlm ventral longitudinal muscle