Fig. 5

Late larval and early juvenile myoanatomy of Leptochiton asellus (Polyplacophora). Apical/anterior faces up in all panels. All panels are maximum intensity projections of confocal image stack subsets. Hatched area of the simplified schematic cross sections in the lower left corner of (a)-(c) indicates the processed confocal image stack subset. Age of depicted specimens is 15 days post hatching (dph) in (a)-(c) and 31 dph in (g) and (h). a Dorsal musculature of a late larva. The pretrochal musculature forms an apical grid (agr). Dorsal insertion sites of the multiple inner dorsoventral muscles (idvm) are clearly visible. b Part of the ventral musculature of a late larva. c Ventral-most musculature of a late larva. d Detail of (a). e Detail of (b). f Detail of (c). g Dorsal musculature of an early juvenile. Note the condensed seven muscle strands of the inner dorsoventral musculature (arrowheads), which are associated with seven juvenile shell plates. h Ventral musculature of an early juvenile. Mantle groove is indicated by dashed line. Note the ventral vestiges of the larval apical grid (agr) in the anterior region. Ventral transversal musculature (vtm) as well as ventrolateral muscles (vlm) are still present in the foot. Abbreviations: apical grid (agr); dorsal transversal musculature (dtm); enrolling muscle (em); inner dorsoventral musculature (idvm); outer dorsoventral musculature (odvm); prototroch muscle ring (ptr); rectus muscle (rem); spicule-secreting cells (sp); ventrolateral muscle (vlm); ventromedian muscle (vmm); ventral transversal musculature (vtm). Scale bars: 50 μm in (a)-(f) and 100 μm in (g) and (h)