Figure 6

Adult musculature of S. roscoffensis . A, B. CLSM micrographs. The bodywall contains longitudinal (lm), circular (cm) and diagonal muscles (dm) in the anterior (A) and posterior (B) dorsal part of the animals, respectively. In the anterior part outer diagonal muscles (odm) are present. Arrowheads mark the filaments of sensory receptor cells, which exhibit a collar of microvilli (inset: arrow), three of which being associated with the rootlet (double arrow); scale bar: 5 μm. C-F. 3D reconstructions. C. Close-up of the ventral surface showing musculature associated with the mouth (asterisk). U-shaped muscles (um) curve around the posterior rim of the mouth. D. Dorsal view of the posterior body region. The bodywall musculature encircles the dorsoventral musculature. E. Detail of the boxed area in (D) showing the arrangement of the dorsoventral musculature (dvm). F. The anterior parenchymal musculature is shown by omitting the dorsal bodywall musculature. Horizontal muscle fibres run from the lateral sides to the midline (hpm), while others fan in longitudinal direction (lpm). Scale bars: 50 μm (A-D, F), 10 μm (E).