Fig. 5.

Summary of Hox gene expression in T. transversa and N. anomala. Schematic drawings of late larvae of T. transversa (A) and N. anomala (B) depicting the expression of each Hox gene. The Hox genes pb (not in N. anomala), Hox3, and Dfd show staggered expression, at least in one of their domains, associated with the mesoderm (light-blue box). In both brachiopods, the genes Scr and Antp are expressed in the periostracum, or the shell-forming epithelium (red boxes), and lab and Post1 are associated to the developing chaetae (green boxes; asterisk in Post1). Post1 is expressed in the chaetae only during late embryonic stages, not in the mature larva, and only in T. transversa. The expression of Lox4 and Post2 in N. anomala could not be determined in this study. The gene Post1 is missing in N. anomala. Drawings are not to scale.