Figure 7
Germ cell labeling with Vasa antibody (Bf-Vasa) during embryogenesis and larval development in B. floridae , and position of mature gonads in three amphioxus species. (A) Bf-Vasa antibody staining showing putative PGCs (arrow, brown signal) at ventral tail bud at N2 neurula stage. Scale bar, 50 μm. (B) Fluorescent immunostaining using Bf-Vasa antibody showing putative PGCs (arrow, red signal) at stage N2. (B′) Higher-magnification image of posterior end of embryo in B, showing putative PGCs. (C) Dorsal view of embryo in B with CellMask counterstaining to show numbers of somites (arrowheads); R, right; L, left. (D-G) PGC staining in 4 days post-fertilization (dpf) larva. Arrows in D, E indicate Vasa-positive cells located near the tail bud. Arrowheads in F, G indicate Vasa-positive cells distributed along myomere boundaries. G Ventral view showing distribution of Vasa-positive cells on both sides of body in B. floridae larva. (H-J) PGC staining in 14 dpf larva. Arrows in H, I indicate Vasa-positive cells located near the tail bud. Arrowheads in J indicate Vasa-positive cells concentrated at the ventral extremity of the myomeres. (J′) Higher-magnification image of ventral tip of myomere, showing putative PGCs. (K) Lateral view of adult amphioxus showing gonad morphology. White dashed line indicates outline of a myomere, while yellow dashed line encircles gonad underneath that particular myomere. (L-N) Position of most anterior gonad (in terms of myomere level) in B. floridae, B. belcheri, and B. japonicum. Photos are left side view of adult amphioxus with the anterior to the left. Red arrowhead indicates first gonad; red dashed line indicates the myomere associated with first gonad; red chevrons indicate anterior gonad-less myomeres. Bar graphs show distribution of myomere positions of first gonad (the most anterior) in three amphioxus species. Sample sizes are indicated under species names.