Figure 5
Expression patterns of Vasa homologs in two Asian amphioxus species ( B. belcheri and B. japonicum ) are mostly identical to that of B. floridae . (A-T) Bb-Vasa and Bj-Vasa expression patterns. Embryos in A, B, D, E, K, L, N, and O are in lateral view with the animal side up and vegetal side down; four-cell stage embryos in C and M are in vegetal view; embryos and larvae in F-J and P-T are in left side view with the anterior to the left. Black arrowheads indicate aggregated maternal Vasa mRNA, while hollow arrowheads indicate zygotic Vasa expression around the blastopore during the gastrula stage. Black arrows indicate expression in the putative PGCs located near the posterior growing zone. White arrows indicate the weak expression of Vasa in the anterior somites. Scale bars, 50 μm. (U-W) Higher-magnification images showing that aggregated maternal Bb-Vasa transcripts are frequently observed in multiple blastomeres in late-cleavage-stage B. belcheri embryos. Arrowheads indicate the individual Bb-Vasa mRNA granules in different blastomeres. Scale bars, 50 μm, can be applied to embryos in the same developmental stage. (X-Y) Distribution of the observed cell numbers harboring the maternal Vasa mRNA granules during B. belcheri and B. japonicum early embryogenesis. The sample size for each developmental stage is shown on top of the graphs.