Fig. 2

Musculature of Pycnophyes kielensis; anterior with introvert inverted. Micrographs obtained with a confocal laser scanning microscope of two kinorhynchs with introvert slightly everted. The musculature was stained with Alexa-488-labeled phalloidin and appears green. a and i are maximum projections, b–h are single scans from the maximum projection shown in A from ventral to dorsal. j–l are single scans from the maximum projection shown in I from ventral to dorsal. Numbers indicate segment number, the animals are oriented with the anterior end upwards, and the scale bar is the same for all micrographs. a P. kielensis with overlay of a musculature over a transmission image to show the position of the muscles relative to the cuticle. b Ventral scan with ventral longitudinal muscles. c Ventral scan slightly more dorsal than b showing the lateral longitudinal muscles between segment 1 and 2. d Ventral view slightly more dorsal than c showing the insertion of the lateral longitudinal muscles on the cuticle in segment 1. e Ventral view slightly more dorsal than d showing the pharyngeal bulb and attached mouth cone muscles. f Dorsal view slightly more dorsal than e with pharyngeal bulb protractor muscles and inner and outer pharyngeal bulb circular muscle layers. g Dorsal view slightly more dorsal than f with placid retractors and DAPI staining in blue to show the position of the brain. h Dorsal view with dorsal longitudinal musculature. i Maximum projection of a specimen with partly everted introvert. j Ventral scan with complete placid retractor muscles. k Longitudinal scan with the mouse cone musculature that is connected to the pharyngeal bulb and overlain by pharyngeal bulb protractor muscles. i Dorsal scan with view on the scalid muscles. dlm dorsal longitudinal muscle, dvm dorsorventral muscle, ipbcm inner pharyngeal bulb circular muscle, llm lateral longitudinal muscle, mcr mouth cone ring muscle, nm neck muscle, opbcm outer pharyngeal bulb circular muscle, mcm mouth cone muscle, pb pharyngeal bulb, pbr pharyngeal bulb retractor, plr placid retractor, pp pharyngeal bulb protractor, ysm y-shaped muscle, vlm ventral longitudinal muscle