Figure 8

Condensation of actin filaments during the differentiation of muscle cells. A, D, G: Early planula. F-actin is weakly pronounced in the mesenteries but not orientated uniformly. B, E, H: In the late planula, F-actin becomes increasingly accumulated and oriented along the oral-aboral axis adjacent to the mesoglea. Moreover, future tentacle cells become enriched in F-actin (B, inlet 1). C, F, I: Early primary polyps show distinct longitudinal muscle strands and increased F-actin accumulation in tentacle muscle cells (C, inlet 1). The parietal muscle and retractor muscle can clearly be identified. Images in A (6 sections), B (8 sections) and C (20 sections) constitute maximum projections. pam, parietal muscle; rem, retractor muscle.