Fig. 2

Embryonic expression of He-elav. a, c, d Nuclei are stained with DAPI (blue). a Maximum projection of a H. exemplaris hatchling showing the central nervous system. The head and first three trunk segments are shown. Neurons are stained with a fluorescent secondary antibody bound to a β-tubulin antibody (red). The scale bar in the bottom left corner of the top panel equals 10 μm. b DIC image of an in situ hybridization targeting He-elav (blue) in a laterally mounted 45 hpl embryo. The dashed line traces the ventral surface of the embryo. c, d Confocal micrographs of He-elav (green) embryos in 45 hpl embryos. c Maximum projection of a laterally mounted embryo. Dashed lines trace the inner and outer brain regions. d, d′ Individual slices from a Z-series showing a frontal view of the head of an embryo. d′ A deeper slice than (d). The solid line in (d) traces the ventral part of the head. The dashed lines trace the inner brain space where neuropil and commissures are found in fully developed brains. e–g Results of in situ hybridizations targeting He-elav at different developmental stages. Arrows point to specimens that are enlarged (inset). In the inset panels, all specimens are laterally mounted, facing right, with anterior toward the top. Arrowheads in the inset panels point to He-elav expression in the developing brain and ventral nerve cord. Dashed lines trace the ventral surface of the specimens in the inset panels. cn, connective; ga1–ga4, ganglion 1–ganglion 4; hpl, hours post-laying; ib, inner brain region; L1–L4, leg 1–leg 4; mo, mouth; ob, outer brain region; st, stomodeal complex