Developmental Neurobiology of the Leech
The leech CNS consists of a ventral chain of 32 segmentally iterated ganglia. The first four and last seven segmental ganglia are fused, constituting a rostral and caudal ganglionic mass, respectively. The rostral ganglionic mass, or subesophageal ganglion, is connected at its anterior end to a dorsally situated supraesophageal ganglion. Each segmental ganglion contains about 400 bilaterally paired neurons, as well as a few unpaired neurons. Their somata form a cortex around the outer surface of the ganglion. The neurons are monopolar; their processes project into a central neuropil, where they make synaptic contacts. From there, the processes of some neurons project to other ganglia via a connective nerve. Sensory and effector neurons project their processes to targets outside the CNS via segmental nerves, whose roots emerge from the lateral edge of the ganglion. In each ganglion, the neuronal somata are distributed over six cell packets, of which two form an anterior and two a posterior pair of lateral packets. The remaining two packets are unpaired, one lying anterior and the other posterior on the ventromedial aspect. Each cell packet contains one giant glial cell, whereas two giant glial cells are associated with the ganglionic neuropil. Additional giant glia are present in the interganglionic connective nerves.
KeywordsHydrogen Peroxide Serotonin Germinal Assure Polypeptide
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- Blair, S.S. and D.A. Weisblat, 1982, Ectodermal interactions during neurogenesis in the Glossiphoniid leech Helobdella triserialis, Develop. Biol., 76:245–262.Google Scholar
- Fitzpatrick-McElligott, S. and G. S. Stent, 1981, Appearance and localization of acetylcholinesterase in embryos of the leech, Helobdella triserialis, J. Neurosci., 1:901–907.Google Scholar
- Kuwada, J.Y. and A.P. Kramer, 1982, Embryonic development of identified leech neurons, submitted for publication.Google Scholar
- Muller, K.J., J.G. Nicholls and G.S. Stent, eds., 1981, Neurobiology of the Leech, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York.Google Scholar
- Schleip, W., 1936, Ontogonie der Hirudineen, in: Klassen und Ordnungen des Tierreichs, Vol. 4, Div. III, Book 4, Part 2, 1–121, H.G. Bronn, ed., Akad. Verlagsgesellschaft, Leipzig.Google Scholar
- Stent, G.S. and D.S. Weisblat, 1982, Cell lineage in the development of the leech nervous system, Trends in Neurosciences, 4(10): 251–255.Google Scholar
- Stent, G.S., D.A. Weisblat, S.S. Blair and S.L. Zackson, 1982, Cell lineage in the development of the leech nervous system, Neuronal Development, N. Spitzer, Ed., Plenum, New York, pp. 1–44.Google Scholar
- Whitman, C.O., 1878, The embryology of Clepsine, Quart. J. Microscop. Sci. (N.S.), 18:215–315.Google Scholar
- Whitman, C.O., contribution to the history of germ layers in Clepsine, J. Morphol., 1:105–182.Google Scholar
- Zackson, S.L., 1982, Cell clones and segmentation in leech development, submitted for publication to Cell.Google Scholar