PATHFINDING OF PERIPHERAL NEURONS IN THE CENTRAL-NERVOUS-SYSTEM OF ANEMBRYONIC GRASSHOPPER (CHORTHIPPUS-BIGUTTULUS)

The peripheral leg nerves of grasshoppers are initially formed by a se t of pioneer neurons and guidepost cells. These cells are used as guid ing structures for later-arising axons of sensory neurons. The develop ment of the central projections of the pioneer cells, the guide-post c ells and some sensory cells is shown with Lucifer Yellow injection or with DiI application. The axons of the pioneer cells Ti1 enter the cen tral nervous system at 38% of embryonic development. They turn anterio rly close to the midline and ascend with no major branching to the bra in. The axons of the guidepost cells Fe1 and Tr1 follow the same path but do not ascend to the brain. Sensory axons of the subgenual organ a nd the femoral organ probably do not follow the central path pioneered by the former neurons. They end ipsilaterally in the respective thora cic neuromere, as is found in the adult.