DEVELOPMENT AND PATHWAY FORMATION OF PERIPHERAL NEURONS DURING LEECH EMBRYOGENESIS
Yueqiao Huang, John Jellies, Kristen M. Johansen and Jørgen Johansen
By labeling the germinal plates of staged leech embryos with monoclonal antibodies to the Ig-superfamily member Tractin we have documented the distribution and initial development of peripheral neurons in a hirudinid leech. We find, in addition to sensillar and extrasensillar sensory neurons, that there are 21 identifiable peripheral neurons in each hemisegment. These neurons are found in highly stereotyped positions and all but two of them are associated with the segmental nerves. We show that eight of the peripheral neurons have the characteristic morphology of stretch receptor neurons and that they form a circumferentially distributed grid aligned in such a way that each of five specialized longitudinal muscle fascicles are monitored by at least two stretch receptor cells covering both ventral, lateral, and dorsal regions of the body wall. Furthermore, we show that in contrast to the dorsal posterior nerve which is pioneered by central projections, the pathways of the three remaining segmental nerves are likely to be pioneered or guided by peripheral neurons.
Huang et al., J. Comp. Neurol. 397:394 (1998) [Full text PDF file]