Polyclad Neurobiology and the Evolution of Central Nervous Systems
The rationale for studying flatworm neurobiology has long been the fact that, anatomically, their nervous systems appear to be intermediate between those of the Cnidarians and the more centralized ones of higher metazoans. It has been thought that understanding flatworm nervous systems would lead to an appreciation of, and insight into, the events involved with the early evolution of brains and central nervous systems. One of the problems of this approach is that the early events that occurred during the initial centralization of nervous systems must have happened so long ago in time that present day organisms can only represent a mere shadow of the actual events. We do not know if centralization occurred several times and independently. Certainly one suspects that the centralization in the Cnidaria and in the Hemichordata might have been independent of those of other metazoans. It is not clear if this also implies that the initial centralization of the protostome and deuterostome lines is independent.
KeywordsInstrumental Conditioning Initial Centralization Response Decrement Multipolar Cell Electrotonic Coupling
Unable to display preview. Download preview PDF.
- Gruber, S., and D. W. Ewer, 1962, Observations on the myo-neural physiology of the Polyclad, Planocera gilchristi, J. exp. Biol. 39:459–477.Google Scholar
- Golubev, A. L., 1988, Glia and neuroglia relationships in the central nervous system of the Turbellaria (Electron microscopic data), in: Free-living and Symbiotic Platyhelminthes (P. Ax, U. Ehlers, and B. Sopott-Ehlers, eds.), Prog. Zool. 36:185–190.Google Scholar
- Hon, H., Muto, A., Osawa, S., Takai, M., Lue, K., and Kawakatsu, M., 1988, Evolution of Turbellaria as deduced from 5S ribosmal RNA sequences, in: Free-living and Symbiotic Platyhelminthes (P. Ax, U. Ehlers, and B. Sopott-Ehlers, eds), Prog. Zool. 36:163–167.Google Scholar
- Koopowitz, H., 1982, The neurobiology of free-living flatworms, in: Electrical Conduction and Behavior in Simple Invertebrates (G. Shelton, ed.), Clarendon Press, Oxford.Google Scholar
- Koopowitz, H., and Chien, P., 1974, Ultrastructure of nerve plexus in flatworms. I. Peripheral organization, Cell. Tiss. Res. 155:337–351.Google Scholar
- Koopowitz, H., and Chien, P., 1975, Ultrastructure of nerve plexus in flatworms. II. Sites of synaptic activity, Cell. Tiss. Res. 157:207–216.Google Scholar
- Kotikova, E. A., 1986, Comparative characterization of the nervous system of the Turbellaria, in: Advances in the Biology of the Turbellarians and Related Platyhelminthes (S. Tyler, ed.), Hydrobiologia 132:82–92.Google Scholar
- Kotikova, E. A., and Joffe, B. I., 1988, On the nervous system of the dalyellioid turbellarians, in: Free-living and Symbiotic Platyhelminthes (P. Ax, U. Ehlers, and B. Sopott-Ehlers, eds.) 36:191–194.Google Scholar
- Reuter, M., 1988, Development and organization of nervous system visualized by immunocytochemistry in three flatworm species, in: Free-living and Symbiotic Platyhelminthes (P. Ax, U. Ehlers, and B. Sopott-Ehlers, eds.), Prog. Zool. 36:181–184.Google Scholar
- Reuter, M., Lehtonen, M., and Wikgren, M., 1986, Immunocytochemical demonstration of 5-HT-like and FMRF-amide-like substances in whole mounts of Micostomum lineare (Turbellaria), Cell Tiss. Res. 246:7–12.Google Scholar