Epitokous transformation of
pygidium. Confocal micrographs, showing acetylated α-tubulin immunoreactivity (green), TRITC-phalloidin stained muscles (red), and cell nuclei (blue). A-B: Pygidia of epitokous females. C-E: Pygidia of epitokous males. A, C, D - view from the dorsal side; B, E - view from the ventral side. vnc - ventral nerve cord; rn - pygidial ring nerve; pc - pygidial commissure; aln - additional pygidial longitudinal nerves; cpm - circular pygidial muscles; acm - additional circular pygidial muscle; opm - oblique pygidial muscles; fp - finger-like protrusions of the male pygidium filled with spermatozoa. Arrowheads show newly formed small longitudinal muscles of the male pygidium. Scale bar 100 μm.