Worm Breeder's Gazette 1(1): 20a
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.
Two young adult animals have been serially sectioned from the tip of the tail forward through the anterior end of the preanal ganglion. The 9 cells of each lumbar ganglion and the 12 cells of the preanal ganglion can be reproducibly identified on the basis of a set of morphological features, including cell body position, direction and extent of fiber projection, fiber size, and cytoplasmic appearance. A total of at least 6 bilaterally homologous pairs can be identified among the lumbar cells. Virtually all the synaptic contacts occur in the preanal ganglion; very few are found in the lumbar ganglia. However, the most prominent participants in these synapses are lumbar cells and a few cells whose bodies lie anterior to the sectioned region; the preanal ganglion cells themselves are relatively minor participants. A complete connectivity matrix has been constructed for both animals, involving about 90 synapses in each case. Certain cells make repeated contacts with one another (up to 13 contacts) in both animals. Other instances of non-reproducible synapses are found, usually involving one contact in one animal and none in the other. Homologously paired cells make similar sets of synaptic contacts. Most (~85/90) of the contacts are diadic, with one presynaptic cell and two postsynaptic ones. Several instances of 'multiple routes of information flow' are found, in which cell A sends to cell C in two ways, both by direct synaptic contact and through an intervening cell, B. No self-synapses are observed, but sensory cells frequently synapse onto their bilateral homologs. One case of reciprocal synapse formation is found. Most of the contacts can be included in a simple wiring diagram by which information flows from sensory cells through multiple routes to converge on a pair of interneurons that apparently constitute one of the major outputs of the system.