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Figure 4 | Frontiers in Zoology

Figure 4

From: Developmental dynamics of myogenesis in the shipworm Lyrodus pedicellatus (Mollusca: Bivalvia)

Figure 4

Myogenesis from late veliger to the early juvenile in Lyrodus pedicellatus (confocal micrographs) . Scale bars: 50 μm. A, B: Lateral view. C: Dorso-lateral view. D: Ventro-lateral view. Anterior up and ventral right, except for C, where ventral is left. (A) Late veliger with paired dorsal (dvr) and ventral velum retractors (vvr). An accessory velum retractor (avr) is attached to the anterior adductor (aa). The pedal plexus (pp) contacts the oral velum musculature (ovm). The pedal plexus projects toward the foot retractor (fr). The posterior adductor (pa) has developed ventrally of the ventral velum retractor. Compact fibres indicate the margin of the mantle musculature (mm). (B) Mid-pediveliger. The velum (v) becomes smaller. The velum ring musculature (vrm) loses its solid appearance. The accessory velum retractor (avr) disappears, the dorsal (dvr) and ventral velum retractor (vvr) are predominant. An accessory adductor (aca) has developed. Pedal plexus and foot retractor have fused and form the foot musculature. The accessory foot retractors (afr) divide halfway into two branches. A diffuse mantle musculature (mm) and a U-shaped mantle musculature (um) originate at the anterior edge of the anterior adductor. (C) Late pediveliger showing disintegration of larval structures. The velum (v) shrinks, the oral velum musculature (ovm) is pushed together, the velum ring musculature disappears. The U-shaped mantle musculature (um), connected to the anterior adductor (aa), elongates. The velum retractors have largely disintegrated, except for one bundle of the ventral velum retractor (vvr). Lateral (lm) and dorsal mantle musculature (dm) lie close to the shell. Foot retractors (fr), accessory foot retractors (afr) and pedal plexus (pp) form the foot musculature. Posterior adductor (pa) and accessory adductor (aca) are well-developed. A finger-shaped mantle musculature (fm) is formed. (D) Early juvenile with velum lost. U-shaped mantle musculature (um) fuses with finger-shaped mantle musculature (fm).

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