Fig. 6

Pallial-like accumulation of glutamatergic neurons in the adult amphioxus brain. a–c Distribution of glutamatergic neurons in one-gill-slit embryos (1GS) detected by in situ hybridisation of VGluT in whole mount preparations. Glutamatergic neurons at these stages are mostly located in the neural tube (arrows), with the exception of a couple of cells located beneath the pigment of the frontal eye, as indicated by the arrowheads. Their ventral position is obvious in a cross section of the same embryo (c) at the level of the dashed line in a and b. d–i Distribution of glutamatergic neurons in the adult amphioxus brain, detected by immunohistochemistry and shown in frontal thick vibratome sections ordered in an anterior-to-posterior direction. Glutamatergic neurons are dorsally restricted in the anterior part of the cv. Neurons in this area can also be observed in the coronal sections shown in Additional file 9 Figure S9. i A magnified view from panel h showing the pseudostratified structure of the neuroepithelium. All scale bars are 20μm. Colour code: red, VGluT/glutamate; green, neuropil and intraventricular cilia (acetylated tubulin); blue/cyan, nuclear staining (Dapi). Abbreviation: np neuropore