Fig. 9

Musculature of the first septum in the competent larva of Siboglinum fiordicum. Surface rendering in AMIRA of the longitudinal muscles of the first septum between trunk segment and the first segment of the opisthosoma. Musculature is shown in red; nuclei stained with DAPI as well as autofluoresce of the opisthosomal chaetae are shown in yellow. A, C Ventral view from the inside the body of the larva. B, D Ventral view from the outside the larva. co—opisthosomal chaetae, mcn—nuclei of large myoepithelial cells of the 1st septum, mls—longitudinal muscles of the first septum, moc1-2—the first and the second circular muscle bundles in opisthosoma, mv—ventral longitudinal strand, mvvl—ventral component of the ventrolateral longitudinal muscle strand, sI—the first septum in the larval ontogenesis, sII—the second septum in order of formation