Literaturdatenbank
Literaturdatenbank |
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Rosenberg, M. E. (1983). Vibration-sensitive receptors in the tortoise’s shell. Journal of Physiology, 346(Supplement), 57P.
Added by: Sarina Wunderlich (18 Nov 2012 17:43:54 UTC) |
| Resource type: Journal Article BibTeX citation key: Rosenberg1983 View all bibliographic details  |
Categories: General Keywords: akustische Kommunikation = acoustic communication, Physiologie = physiology, Schildkröten = turtles + tortoises, Testudinidae, Testudo, Testudo graeca, Testudo hermanni Creators: Rosenberg Collection: Journal of Physiology |
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| URLs http://jp.physoc.o ... ement/23P.full.pdf |
| Abstract |
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Testudinidae Testudo The existence of a sensory innervation within the outer layers of the tortoise's sheIl was recently revealed by means of evoked potentials (Rosenberg, 1978, 1980). It was shown that the responses were mediated by the larger-diameter fibres of the afferent nerve. The present experiments utilized the recording of unitary discharges of peripheral nerve fibres to obtain more information about the properties of the receptors. The observations were made on eight decerebrate-spinal animals (T. graeca and T. hermanni) ; the length of the carapace was 105-180 mm (mean 140 mm). Ambient (and body) temperature, in different experiments, was 19-26°C (mean 23°C). The discharges of sensory fibres were detected in the nerves supplying the shell. The territories examined were in the costal and marginal (epidermal) shields of the carapace and in the abdominal shield of the plastron: each of these regions exhibited sensitivity to 10caIly applied mechanical stimulation. Stroking the surface of the sheIl with a soft brush was an adequate local stimulus to cause firing in afferent nerve fibres; this was the method used for preliminary identification of a receptive site. The sensory units were rapidly adapting but they could be fired repeatedly and in synchrony with a vibratory stimulus (applied with a moving-coil-driven probe, tip diameter 0·4 mm). Frequency response to vibration was tested at 16 sites of high sensitivity. At aIl but two sites the sensory units could be synchronously driven up to 20 Hz and at 5 sites up to 70 Hz. Vibration at 150 Hz or more produced little or no firing. Receptive fields were mapped, using the vibrating probe, at uniform intensity and frequency (7-15 Hz). Twenty-one receptive sites were so examined, twelve related to presumed single afferent fibres and the remainder to multiple fibres. Response maxima were found to be sharply localized with respect to the surface of the sheIl: cut-off to 50 % of maximum response occurred over a distance of only 1-2 mm. Sensitive sites were found both in central and in peripheral parts of the epidermal shields but the greatest density of innervation seemed to be towards the edges of the shields. The actual grooves or junctions between adjacent shields were found, surprisingly, rwt to be places of special sensitivity. The sheIl of the tortoise appears thus weIl endowed with a mechanosensitive surface consistent with good localizing ability for innocuous body contact. Possibly the sensitivity to vibration, particularly in the plastron, is important in the detection of ground-born acoustic waves.
Added by: Sarina Wunderlich |