Worm Breeder's Gazette 9(3): 109
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.
We previously reported that ablation of the BDU cells at hatching disrupts the ability of the postembryonic touch cell AVM to mediate a head touch response (CSH meeting, 1985). This dependence of AVM on the BDU cells is restricted to early postembryonic development, as removal o at 24 hours or more after hatching no longer affects the touch sensitivity mediated by AVM. We have examined in the electron microscope AVM neurons that have grown in the absence of the BDU cells and found a range of changes in the morphology of the synaptic branch. Five animals were examined: one had a normal synaptic branch directed toward the nerve ring; a second had a small, anteriorly displaced branch that appeared to enter one of the circumferential commissures In the other three no sign of a synaptic branch was seen We interpret these results to mean that the process giving rise to the synaptic branch of the postembryonic AVM is dependent upon the presence of the BDU neurons BDU may affect AVM development in two ways. First, the BDU cell may induce the formation of the synaptic branch. Alternatively, BDU may provide a path into the nerve ring and the synapses formed between these cells serve both to stabilize the branch and to guide it through an essentially mature nerve ring In the absence of the stabilizing influence the branch must find an alternative to survive Because branches were present in two of the five animals we examined and because based on adult reconstructions White, et al , 1986) the AVM process appears to branch before contacting the BDU cell, we favor the second hypothesis