Skip to main content
Figure 4 | EvoDevo

Figure 4

From: What is a segment?

Figure 4

Annelid, arthropod, and vertebrate heads. (A) The segmental nature of the anterior region, or ocular lobe, of the arthropod head is disputed (orange). Ventral view of a 96-hour Parhyale embryo. Definitively segmented head segments are shaded in gray (antennae 1, antennae 2, mandibles, maxillae 1, maxillae 2, and the maxillipeds). (B, C) Annelids have an unsegmented anterior region, or prostomium (yellow). Lateral view of a polychaete trochophore larva (B), and ventral view of the anterior region of an earthworm (C after [54]). (D) Vertebrates have head structures with segmental characteristics, such as the rhombomeres (red) and pharyngeal arches (blue). Lateral view of the anterior region of a 24-hour zebrafish embryo, head slightly curved ventrally. a, anterior; p, posterior.

Back to article page