File:The Biological bulletin (19757343833).jpg

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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Figure 2. Cross-sections through the paired original (a, hi claws of a juvenile 6th stage lobster and through the paired regenerated (c. d) claws of another 6th stage lobster in which the claws had been removed in the 4th and 5th stages. Histochemical detection of myofibrillar ATPase activity shows fast fibers staining more intensely than slow, and hence the small, dorsally located opener muscle (arrow) is entirely slow while the large closer muscle occupying most of the cross-sectional area has a central band of fast fibers sandwiched dorsally and ventrally by slow fibers. The fast band varies considerably in size between the paired original muscles being narrow in the putative crusher muscle (a) and broad in the putative cutter muscle (b). In the paired regenerate muscles, however, the fast band is similar in size. Magnification 25X. stage), however, the regenerate muscles have not com- pletely differentiated into cutter types in the subsequent 3-5 stages. Thus the absence of the muscle during the critical juvenile stages results in regenerate phenotype being retarded. How long the muscle is retarded appears to depend on how often the claws are lost; when lost for two successive stages, the retardation is temporary but when lost over several successive stages, the retardation is more permanent. A few of the regenerate muscles had slow fibers inter- spersed in the fast muscle band, giving rise to a mosaic distribution of these two types of fibers. This is an unusual distribution of fast and slow fibers in the closer muscle of lobsters as well as other decapod crustaceans. Thus, in the claw closer muscle of lobsters (Ogonowski el ill., 1980), crayfish (Govind and Pearce, 1985), snapping shrimps (O'Connor el til. 1984), and hermit crabs (Stephens el al. 1984), fast and slow muscle is regionally distributed; the fast fibers are restricted to a band in the central region. The closer muscle in the more anterior walking limbs in lobsters (Mearow and Govind, 1986) and hermit crabs (Stephens el ill. 1984) have a similar pattern. In no in- stance has a mosaic distribution of fast and slow fibers in the closer muscle been reported in the above mentioned species. Apart from the closer muscles listed above containing discrete populations of fast and slow fibers, other muscles that have been examined are composed of a single fiber type, e.g., the abdominal extensor and flexor systems that have separate fast and slow muscles in tailed crustaceans (Govind and Atwood, 1982). Consequently, the appear- ance of a mosaic distribution of fiber types is an uncom- mon finding among decapod crustaceans. That such a mosaic pattern occurs only in regenerated closer muscles and not in the originals suggests that the instructions for differentiating an entire muscle are not as robust as those
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Figure 3. Cross-sections through the paired original (a, b) claws of a juvenile 8th stage lobster and through the paired regenerated (c, d) claws of another 8th stage lobster in which the claws had been removed in the 4th, 5th, 6th, and 7th stages. The proportion of fast fibers is highly asymmetric in the paired original closer muscles being restricted to a narrow central band in the crusher claw (a) but widespread in the cutter claw (b). In the paired regenerate muscles, however, the band of fast fibers is symmetric. Magnification 15X.

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