Figure 4

AmphiSyn expression in amphioxus neurulae. Whole mounts in side views, except for B and M in dorsal view, anterior is to the left. Cross sections counterstained pink are viewed from the caudal end of the animal. Whole mount and cross section scale bars are 50 and 25 μm, respectively. A, B: 14-hour neurula showing expression in four spots of the neural plate at the somite boundaries, beginning at S1/2 (between somites 1 and 2) and extending to S4/5. C: Cross section through level c in A, showing a pair of ventrolateral labeled cells. D: Enlargement of 16-hour neurula showing a new cluster of labeled nerve cells at level of the posterior part of somite 1. E: In 18-hour neurula AmphiSyn expression extends in the posterior neural tube and a new expression appears in single epidermal cells in the ventro-lateral region of the embryo. F-K: Cross sections trough levels shown in E. The labeled sensory cells are mostly confined into the subepidermic layer (black arrowheads). Few positive sensory cells were located in epidermal layer (red arrowheads). In the nerve cord, labeled cells were mainly located ventrolaterally (F-I), except for few cells located dorsolaterally (E, G). L: In 20-hour neurula the most caudal epidermal labeled cells showed a periodically arrangement following the somite boundaries (red arrowheads in L). M: Dorsal view of two-thirds of the specimen in L. N-P: Cross sections through levels shown in L and M.