Fig. 16

Histological sections through the inner mantle fold of Nodipecten nodosus. Sequence of sections (B–E) from proximal to distal region, showing gradual increase in margin-parallel musculature towards distal. Toluidine blue and basic fuchsin. a Schematic representation of the mantle margin, specifying the regions from the inner mantle fold that correspond to the sections seen in B–E. Ventral to the top. b Radial muscles from the mantle extend into the base of the inner fold. c At intermediate levels of the inner fold, there is a combination of radial and margin-parallel muscles. d Towards the margin, the connective tissue is reduced and margin parallel muscles increase in volume. e In the distal region, the radial muscles are compressed and margin-parallel muscles predominate. Abbreviations: rm, radial muscles; mp, margin parallel muscles