Michalis Averof and Nipam Patel compared the expression of Ubx-AbdA Hox genes in different thorax segments during embryonic development in four crustaceans. To probe the question of maxillipeds further, Averof, Patel, and colleagues turned to an emerging model organism: a small type of crustacean called an amphipod. The photo at the beginning of this case study shows a ventral view of the expression pattern of Ubx (red area) in an amphipod embryo. In which tagma does Ubx appear to be expressed>