Conserved and novel functions for Netrin in the formation of the axonal scaffold and glial sheath cells in spiders

► Axonal tracts form in the same sequence in spiders, insects and crustaceans. ► Cs netrin expression is adapted to the morphology of the spider ventral midline. ► Cs netrin shows a conserved function in axonal guidance at the ventral midline. ► We show a novel function of Cs netrin in the formation of glial sheath cells. ► Loss of glial sheath cells leads to premature segregation of neural precursors.