Title: The Biological bulletin
Identifier: biologicalbullet180mari (find matches)
Year: [1] (s)
Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983
Subjects: Biology; Zoology; Biology; Marine Biology
Publisher: Woods Hole, Mass. : Marine Biological Laboratory
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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32 C. K. GOVIND ET AL
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Figure 4. Cross-sections through the claws of two juvenile 8th stage lobsters (a. h) showing different degrees of interspersion of slow fibers (light staining) in the hand of fast fibers (dark-staining), resulting in a mosaic appearance in the closer muscle. Magnification 35x. for differentiating individual fiber types. Perhaps along similar lines is our observation that in the regenerated chelipeds of adult lobsters, the main limb nerve will often travel in a scattered, diffuse fashion rather than in discrete bundles. Although haphazard in appearance, the regen- erated nerve contains the requisite motor and sensory neurons. While a mosaic distribution of fiber types within a muscle occurs rarely in crustaceans, it is commonplace among vertebrates where individual limb muscles are in- nervated by a large number of motor neurons (Burke, 1981). Despite being randomly distributed within the muscle, fibers comprising a motor unit are of the same type. This has led to the suggestion that the innervating neuron regulates muscle fiber properties. Such neuro- trophic regulation in the lobster claw closer muscle is un- likely as there are only two excitor neurons (Wiersma, 1961), both of which distribute to most of the muscle fibers (Govind and Lang, 1974). Our findings also underscore the very robust nature of the regenerative capacity among juvenile lobsters. Apart from the slowing down in muscle differentiation and the occasional appearance of a mosaic distribution of fiber types, conditions that may be ameliorated, the regenerate muscle otherwise resembles its original counterpart. Thus, the loss of claws seen particularly in the early juvenile stages does not appear, in the long term, to impede the differentiation of a typical phenotype in the closer muscle. Acknowledgments We thank Michael Syslow and Kevin Johnson for gen- erous supplies of larval lobsters and the Natural Sciences and Engineering Research Council of Canada for financial support. Literature Cited Burke, R. K. 1981. Motor units: anatomy, physiology and functional units. Pp. 345-422 in Handbook oj Physiology: The Nen'ous System. Vol. II. J. M. Brookhart and V. B. Mountcastle, eds. Williams and Wilkens. Baltimore. Kmmel, V. E. 1908. The experimental control of asymmetry at different stages in the development of the lobster. J. Exp. Zoo/- 5: 471-484. Govind, C. K. 1984. Development of asymmetry in the neuromuscular system of lobster claws. Bwl Bull. 167: 94-119. Govind, C. K. 1989. Asymmetry in lobster claws. Am. Sci. 77: 468- 474. Govind, C. K., and H. L. Atwood. 1982. Organization of the neuro- muscular system. Pp. 63-103 in The Biology of Crustacea I '/. 3.. Neurobiology: Structure and Function, D. E. Bliss, H. L. Atwood, and D. C. Sandeman. eds. Academic Press. New York. Govind. C. K., and K. S. Kent. 1982. Transformation of fast fibres to slow presented by lack of activity in developing lobster muscle. Nature 298: 755-757. Govind, C. K., and F. Lang. 1974. Neuromuscular analysis of closing in the dimorphic claws of the lobster. Homams americanus. J Exp. Zoo/. 190: 281-288. Govind, C. K., and F. Lang. 1978. Development of the dimorphic claw closer muscles of the lobster llomarus americanus. III. Transfor- mation to dimorphic muscles in juveniles. Biol. Bull 154: 55-67.

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