Worm Breeder's Gazette 3(1): 18b

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Ventral Cord Motor Neurone Ablation Experiments

J. White

There are only three out of the adult complement of five classes of 
motor neurone present in the ventral cords of L1 juveniles.  The total 
of 15 cells is made up of 5 DB's, 6 DA's and 4 DD's.  The sequence of 
cell types is invariant in juvenile cords thus enabling cells to be 
identified in live animals by their relative positions in the cord.  
All cells of a particular class were killed by means of a laser 
microbeam and any subsequent alterations in behavior observed.  It was 
found that larvae with ablated DA's could not back up but moved 
forward normally, whereas those without DB's had difficulty moving 
forward but showed normal backing behavior.  The latter effect is 
somewhat masked by head movements which were always normal.  Animals 
without DD's were severely uncoordinated when moving in either 
direction.  These observations are in accord with the predictions of 
Dick Russel's model of the functioning of the ventral cord.