Fig. 2

Myoanatomy of pediveligers of Nodipecten nodosus. Anterior to the top and ventral to the right in (a), (b), and (d). Ventral to the top in (c). a Confocal micrograph of the musculature of a pediveliger larva. Lateral view. b Transmission electron micrograph of the striated fibers of the velum retractor; asterisks indicate the Z-lines defining sarcomere limits. c Light micrograph of a semithin cross-section through a pediveliger showing the posterior and anterior adductor fibers. Toluidine blue and basic fuchsin (TB). d 3D reconstruction of the musculature of a pediveliger larva showing mantle muscles, adductors formed by striated and smooth portions, and foot retractor with combined arrangement of bundles originating from the median region (arrowhead) and from the posterior adductor region (arrow). Lateral view. Larval retractors (i.e., velum retractors and ventral retractors) are depicted in dark green to allow for prominent visualization of other muscle groups. Abbreviations: aa, anterior adductor; mm, mantle margin-parallel muscles; mr, mantle retractors; pa, posterior adductor; sm, smooth portion; st, striated portion; vl, ventral larval retractor; vr, velum retractors