Fig. 20

Himasthla elongata cercariae, spine musculature. a: oblique optical slice through the body wall (ventral side, preacetabular region); b: superficial frontal optical section through middorsal collar spines; c: deeper frontal optical section through middorsal collar spines; d: scheme showing the arrangement of muscle fibers connected with collar spines. bws – bow-shaped muscle fibers of the collar spines; cm – circular muscle fibers; crs – criss-cross muscle fibers of the collar spines; csp – collar spines; dm – diagonal muscle fibers; lm – longitudinal muscle fibers; prs – protractors of the collar spines; spm – muscle fibers connected with tegumental spines. Scale bars 10 μm