Do Glial Cells Exist in the Nervous System of Parasitic and Free-Living Flatworms? An Ultrastructural and Immunocytochemical Investigation
Abstract
It is still unclear whether flatworms have specialized glial cells. At present there are no special methods available for the identification of glial cells in flatworms. The aim of this research was to carry out detailed investigations of the CNS in two species of cestodes, and to get an idea whether these cells may fit into the concept of glia. Three types of glial cells have been found in Grillotia erinaceus: (1) fibroblast- like cells in the cerebral ganglion (CG); (2) glial cells in bulbar nerves with filaments and laminar cytoplasm; (3) a 3rd type of cells forms multilayer envelopes in the main cords (MC); also they make contacts with the excretory epithelium. To demonstrate the existence of glial cells, an immunocytochemical and ultrastructural investigation of Ligula intestinalis was undertaken. Intensive S100b-like immunoreaction (IR) was found in the GG and in the MC. IR-varicosities were mostly located asymmetrically on the MC, and no IR was found in neuropiles. Small glial cells were found on the surface of the MC; they have oval nuclei and dense cytoplasm with slim processes going around the neuropile and enclosing neurons. Long junctions are seen between cell processes but with neurons they usually possess juxtaposition contacts. Glial cells lack vesicles or synapse-like structures. Intensive S100b-like-IR has been shown in the CNS of cestodes for the first time. Results from ultrastructural research support the immunocytochemical date.
Keywords
Glia flatworms S100b ultrastructure immunocytochemistryAbbreviations
- A
axon
- CG
cerebral ganglion
- GAx
giant axon
- EX
excretory vessel and cells
- F
fibrillar matrix
- GC
glial cell
- GP
glial processes
- InM
invaginations of the neuron membrane
- M
muscle cells and processes
- MC
main nerve cord
- Mh
mitochondria
- N
neuron
- NP
nervous processes
- npl
neuropile
- Nu
nucleus
- L
lipid drop
- sy
synapse
- T
tegument and subtegument
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References
- 1.Bedini, C., Lanfranchi, A. (1998) Ultrastructural study of the brain of a Typhloplanid flatworm. Acta Zool (Stock). 79, 243–249.CrossRefGoogle Scholar
- 2.Biserova, N. (2000) The ultrastructure of glia-like cells in lateral nerve cords of adult Amphilina foliacea (Amphilinida). Acta Biol. Hung.. 51, 439–442.PubMedGoogle Scholar
- 3.Biserova, N. (2000) Do glia cells exist in parasitic flatworms? Europ. J. Neurosci. 12, 11, 354.Google Scholar
- 4.Biserova, N., Korneva, J. (2006) The nervous system ontogeny in cestodes and amphilinids. Invertebrate Zool.. 3, 157–184.CrossRefGoogle Scholar
- 5.Biserova, N., Salnikova, M. (2002) The ultrastructure of main lateral nerves cords and associated cell elements in Triaenophorus nodulosus (Cestoda: Pseudophyllidea). Cytologia. 44, 611–622.Google Scholar
- 6.Bockerman, I., Reuter, M., Timoshkin, O. (1994) Ultrastructural study of the central nervous system of endemic Geocentrophora (Prorhynchida, Platyhelmintes) from Lake Baikal. Acta Zool. (Stockh). 75, 47–55.CrossRefGoogle Scholar
- 7.Coles, J. A., Abbott, N. J. (1997) Signaling from neurons to glial cells in invertebrates. General Pharmacology: The Vascular System. 29, 39–47.CrossRefGoogle Scholar
- 8.Cooper, M. (1996) Intercellular signaling in neuronal-glial networks. Brain Research. 716, 53–58.CrossRefGoogle Scholar
- 9.Ferrero, E., Lanfranchi, A., Bedini, C. (1985) An ultrastructural account of otoplanid Turbellaria neuroanatomy. I. The cerebral ganglion and the peripheral nerve net. Acta Zool. (Stockh). 66, 63–74.CrossRefGoogle Scholar
- 10.Golubev, A. (1982) Electron Microscopy of the Nervous System in Worms. Kazan. Publishing house of the Kazan State University.Google Scholar
- 11.Halton, D., Gustafsson, M. (1996) Functional morphology of the platyhelminth nervous system. Parasitology. 113, 47–72.CrossRefGoogle Scholar
- 12.Halton, D., Maule, A., Shaw, C. (1997) Trematode Neurobiology. In: Fried, B., Graczyk, Th. (eds) Advances in Trematode Biology. CRC Press. N.Y. pp. 345–381.Google Scholar
- 13.Koopowitz, H. (1986) On the evolution of central nervous systems: Implications from polyclad turbellarian neurobiology. Hydrobiologia. 132, 79–87.CrossRefGoogle Scholar
- 14.Michetti, F., Cocchia, D. (1982) S-100-like immunoreactivity in a planarian. Cell Tissue Res.. 223, 575–582.CrossRefGoogle Scholar
- 15.Pentreath, V. (1989) Invertebrate glial cells. Comp. Biochem. Physiol. A 93. 1, 77–83.CrossRefGoogle Scholar
- 16.Reuter, M. (1990) From innovation to integration. Trends of the integrative system in microturbellarias. In: Gustafsson, M., Reuter, M. (eds) The Early Brain. Åbo Acad. Press, pp. 161–178.Google Scholar
- 17.Riehl, B., Schlue, W. (1998) Morphological organization of neuropile glial cells in the central nervous system of the medicinal leech (Hirudo medicinalis). Tissue and Cell. 30, 177–186.CrossRefGoogle Scholar
- 18.Rohde, K. (1971) Untersuchungen an Multicotyle purvisi Daves, 1941 (Trematoda: Aspidogastrea). III. Licht- und elektronmikroskopischer Bau des Nervensystems. Zool. Jahrb. Anat.. 88, 320–363.Google Scholar
- 19.Rohde, K., Webb, R. (1986) Ultrastructure of neuroglia in the peripheral nervous system of Temnocephala sp. (Turbellaria, Temnpcephalida). Zool. Anz.. 216, 53–57.Google Scholar
- 20.Sukhdeo, S., Sukhdeo, M. (1994) Mesenchyme cells in Fasciola hepatica (Platyhelminthes): primitive glia? Tissue and Cell. 26, 123–131.CrossRefGoogle Scholar
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