Summary
Whip spiders (Amblypygi) are arachnids with a specialized first pair of legs. These legs are unusually long (20–25 cm) and are not used for walking. Instead their lengthy tarsi (7–8 cm) are covered with thousands of sensory hairs (mechano- and chemoreceptors). The legs thus resemble antennae of insects. Each sensory hair is associated with 4–40 neurons whose axons are grouped together to form two large tarsal nerves. The nerves contain about 23 000 sensory axons. Whereas most of the axons measure only 0.1–0.2 μm in diameter, a few are exceptionally large (3–20 μm). These are giant fibres. Their large somata are located in specific segments of the tarsi. The branched dendrites of the giant neurons receive hundreds of chemical synapses, presumably from the sensory axons of the hair sensilla. Since stimulation of the tarsal tip elicits fast withdrawal reaction (⩾80 ms), it is likely that the giant fibres provide the pathway for the rapid conduction of nerve impulses to the motor centres of the C.N.S. The system is comparable to the giant fibre system of certain insects. In contrast, however, the giant interneurons and associated synapses of whip spiders are not located in the C.N.S., but lie some 20 cm removed in the periphery. Thus, some primary sensory information already becomes processed in the peripheral nervous system, before it reaches the C.N.S.
Similar content being viewed by others
References
Babu, K. S. (1961) ‘Giant’ fibres in the central nervous system of scorpion.Journal of Animal Morphology and Physiology 8, 11–8.
Beck, L. &Görke, K. (1974) Tagesperiodik, Revierverhalten und Beutefang der GeißelspinneAdmetus pumilio C. L. Koch im Freiland.Zeitschrift für Tierpsychologie 35, 173–86.
Beck, L., Foelix, R., Gödeke, E. &Kaiser, R. (1977) Morphologie, Larvalentwicklung und Haarsensillen der GeißelspinneHeterophrynus longicornis Butler (Arach., Amblypygi).Zoomorphologie 88, 259–76.
Bliss, C. I. (1967)Statistics in Biology. New York: McGraw-Hill.
Boeckh, J., Ernst, K.-D., Sass, H. &Waldow, U. (1976) Zur nervösen Organisation antennaler Sinneseingänge bei Insekten unter besonderer Berücksichtigung der Riechbahn.Verhandlungen der Deutschen Zoologischen Gesellschaft 1976, 123–39.
Bullock, T. H. &Horridge, G. A. (1965)Structure and function in the Nervous Systems of Invertebrates. Vol. II. San Francisco, London: Freeman.
Cahmi, J. M. &Tom, W. (1978) The escape behaviour of the cockroachPeriplaneta americana I. Turning response to wind puffs.Journal of Comparative Physiology 128, 193–201.
Castel, M., Spira, M. E., Parnas, I. &Yarom, Y. (1976) Ultrastructure of region of low safety factor in inhomogeneous giant axon of the cockroach.Journal of Neurophysiology 39, 900–8.
Drewes, C. D., Landa, K. B. &McFall, J. L. (1978) Giant nerve fibre activity in intact, freely moving earthworms.Journal of Experimental Biology 72, 217–27.
Esslen, J. &Kaissling, K.-E. (1976) Zahl und Verteilung antennaler Sensillen bei der Honigbiene (Apis mellifera L.).Zoomorphologie 83, 227–51.
Fahrenbach, W. H. (1979) The brain of the horseshoe crab (Limulus polyphemus) III. Cellular and synaptic organization of the corpora pedunculata.Tissue and Cell 11, 163–200.
Foelix, R. F. (1975) Occurrence of synapses in peripheral sensory nerves of arachnids.Nature 254, 146–8.
Foelix, R. F. (1976) Rezeptoren und periphere synaptische Verschaltungen bei verschiedenen Arachnida.Entomologica Germanica 3, 83–7.
Foelix, R. F. &Choms, A. (1979) Fine structure of a spider joint receptor and associated synapses.European Journal of Cell Biology 19, 149–59.
Foelix, R. F., Chu-Wang, I.-W. &Beck, L. (1975) Fine structure of tarsal sensory organs in the whip spiderAdmetus pumilio (Amblypygi, Arachnida).Tissue and Cell 7, 331–46.
Foelix, R. F. &Hauser, M. (1979) Helically twisted filaments in giant neurons of a whip spider.European Journal of Cell Biology 19, 303–6.
Govind, C. K. &Lang, F. (1976) Growth of lobster giant axons: Correlation between conduction velocity and axon diameter.Journal of Comparative Neurology 170, 421–34.
Graziadei, P. P. C. &Gagne, T. H. (1976) Sensory innervation in the rim of the octopus sucker.Journal of Morphology 150, 639–80.
Griffin, A. J. &Fahrenbach, W. H. (1977) Gill receptor arrays in the horseshoe crab (Limulus polyphemus).Tissue and Cell 9, 745–50.
Günther, J. (1976) Impulse conduction in the myelinated giant fibres of the earthworm. Structure and function of the dorsal nodes in the median giant fibre.Journal of Comparative Neurology 168, 505–32.
Hayes, W. F. (1971) Fine structure of the chemoreceptor sensillum inLimulus.Journal of Morphology 133, 205–40.
King, D. G. (1977) An interneuron inDrosophila synapses within a peripheral nerve onto the dorsal longitudinal muscle motor neurons.Neuroscience Abstracts 3, 180.
Matsumoto, S. G. &Murphey, R. K. (1977) The cercus-to-giant interneuron system of crickets IV. Patterns of connectivity between receptors and the medial giant interneuron.Journal of Comparative Physiology 119, 319–30.
Murphey, R. K. &Palka, J. (1974) Efferent control of cricket giant fibres.Nature 248, 249–51.
Palka, J. &Olberg, R. (1977) The cercus-to-giant interneuron system of crickets III. Receptive field organization.Journal of Comparative Physiology 119, 301–17.
Parnas, I. &Dagan, D. (1971) Functional organization of giant axons in the central nervous system of insects: New aspects.Advances in Insect Physiology 8, 95–143.
Ritzmann, R. E. &Camhi, J. M. (1978) Excitation of leg motor neurons by giant interneurons in the cockroachPeriplaneta americana.Journal of Comparative Physiology 125, 305–16.
Roeder, K. (1948) Organization of the ascending giant fibre system in the cockroach (Periplaneta americana).Journal of Experimental Zoology 108, 243–61.
Roeder, K. (1963)Nerve Cells and Insect Behavior. Cambridge, Massachusetts: Harvard University Press.
Schaller, D. (1978) Antennal sensory system ofPeriplaneta americana L. Distribution and frequency of morphologic types of sensilla and their sex-specific changes during postembryonic development.Cell and Tissue Research 191, 121–39.
Steinbrecht, R. A. (1969) On the question of nervous syncitia: Lack of axon fusion in two insect sensory nerves.Journal of Cell Science 4, 39–53.
Valentino, K. L. (1977) Identified neurons make identical synapses inMusca andDrosophila.Neuroscience Abstracts 3, 190.
Westin, J., Langberg, J. &Camhi, J. (1977) Responses of giant interneurons of the cockroachPeriplaneta americana to wind puffs of different directions and velocities.Journal of Comparative Physiology 121, 307–24.
Wiese, K., Calabrese, R. L. &Kennedy, D. (1976) Integration of directional mechanosensory input by crayfish interneurons.Journal of Neurophysiology 39, 834–43.
Wood, M. R., Pfenninger, K. H. &Cohen, M. J. (1977) Two types of presynaptic configurations in insect central synapses.Brain Research 130, 25–45.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Foelix, R.F., Troyer, D. Giant neurons and associated synapses in the peripheral nervous system of whip spiders. J Neurocytol 9, 517–535 (1980). https://doi.org/10.1007/BF01204840
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01204840