Morphology, Ultrastructure and Contractile Properties of Muscles Responsible for Superior Tentacle Movements of the Snail
Bending, twitching and quivering are different types of tentacle movements observed during olfactory orientation of the snail. Three recently discovered special muscles, spanning along the length of superior tentacles from the tip to the base, seem to be responsible for the execution of these movements. In this study we have investigated the ultrastructure, contractile properties and protein composition of these muscles. Our ultrastructural studies show that smooth muscle fibers are loosely embedded in a collagen matrix and they are coupled with long sarcolemma protrusions. The muscle fibers apparently lack organized SR and transverse tubular system. Instead subsarcolemmal vesicles and mitochondria have been shown to be possible Ca2+ pools for contraction. It was shown that external Ca2+ is required for contraction elicited by high (40 mM) K+ or 10−4 M ACh. Caffeine (5 mM) induced contraction in Ca2+-free solution suggesting the presence of a substantial intracellular Ca2+ pool. High-resolution electrophoretic analysis of columellar and tentacular muscles did not reveal differences in major contractile proteins, such as actin, myosin and paramyosin. Differences were observed however in several bands representing presumably regulatory enzymes. It is concluded that, the ultrastructural, biochemical and contractile properties of the string muscles support their special physiological function.
KeywordsString muscles Helix ultrastructure contractile properties contractile proteins
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- 2.Brooks, D. D., Huddart, H., Lennard, R., Hill, R. B. (1990) Calcium utilization in contractures induced by acetylcholine or high-potassium saline in molluscan proboscis muscles. J. Exp. Biol. 149, 379–394.Google Scholar
- 5.Chen, C.-J. (1983) A study of the longitudional body wall muscle of the sea cucumber Sclerodactyla briareus. PhD thesis, University of Rhode Island, USA.Google Scholar
- 9.Frescura, M., Hodgson, A. N. (1989) On collagen and its potential role in the columellar muscle of some gastropod molluscs. Suid-Afrikaanse Tydskrif Vir Wetenskap, 85, 613–614.Google Scholar
- 15.Kier, W. M. (1992) Hydrostatic skeletons and muscular hydrostats. In: Biewener, A. A. (ed.) Biomechanics (Structure and Systems): A Practical Approach. Oxford Univ. Press, New York, pp. 205–231.Google Scholar
- 23.Motokawa, T. (1982) Factors regulating the mechanical properties of holothurian dermis. J. Exp. Biol. 99, 29–41.Google Scholar
- 30.Zakharov, I. S. (1992) Avoidance behavior of the snail. J. Higher Nerv. Act. 42, 1156–1169. (in Russian)Google Scholar
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