Fig. 10. Stages 20–22 in Development and gastrulation in Hyloxalus vertebralis and Dendrobates auratus (Anura: Dendrobatidae)

Fig. 10. Stages 20–22: External gill development in H. vertebralis. (A) Stage 20: Circulation to the external gills. Three branches were visible in the first gill pair. The second gill pair was unbranched. (B) Stage 22: The external gills enlarged. Seven branches were visible in the first gill pair. The second gill pair was unbranched. (C) Stage 20: Horizontal section at the level of the brain. (D) Stage 22: Horizontal section at the level of the internal gills. bn, brain; ey, eye; ec, ectoderm; fg, first gill pair; g, internal gill; nt, notochord; ot, otocyst; s, somite; sg, second gill pair.