Connectivity changes in a class of motoneurone during the development of a nematode

THE ventral nerve cord of the nematode Caenorhabditis elegans contains a linear array of motoneurones (Fig. 1) which innervate the body muscles that mediate locomotion. The adult ventral cord has about three times as many cells as that of the first stage larva. The development events that generate the adult complement of cells occur in a period preceding the first larval moult. During this period we find that a class of pre-existing, juvenile motoneurones changes its pattern of connectivity. Neuromuscular junctions are removed from ventral muscles and are reformed onto dorsal muscles. Similarly the dendritic input to these neurones changes over from the dorsal to the ventral side.