VGLUT expression in developing amphioxus embryos. Whole mounts with anterior to the left (scale bars = 50 μm) and cross-sections (scale bars = 25 μm) viewed from the caudal end of the animal. A: 14-hr neurula showing expression in single ectodermal cells in the ventrolateral region and in three spots of the neural tube (arrows). B: 16-hr neurula with expression in three spots of the neural tube (arrows). C: Dorsal view of the embryo in B showing three pairs of VGLUT positive neurons in the neural tube (arrows). D: Side view of a 22-hr neurula. E: Magnification of the anterior part of the embryo in D, showing expression in three cell clusters of the cerebral vesicle (CV) and in several neurons located in close proximity to the first pigment spot. Labeled ectodermal sensory cells are conspicuous near the first pigment spot. F-H: Consecutive transverse sections starting at the level of f in E. I: Anterior end of a 24-hr larva. J-O: Transverse sections at levels indicated in I. P: 36-hour larva. Several labeled sensory cells are visible along the body of the larva and at the tip of the rostrum. VGLUT transcripts are also detectable in cells of the frontal eye complex (arrow), in neurons of the posterior cerebral vesicle (black arrowhead) and in cells of the neural tube anterior (red arrowhead) and posterior (yellow arrowhead) to the first pigment spot. N, notochord. The first pigment spot in E, N and P is indicated by a red arrowhead.