REGIONAL DISTRIBUTION OF MUSCLE FIBER TYPES IN THE ASYMMETRIC CLAWS OF CALIFORNIAN SNAPPING SHRIMP

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Abstract
The properties of the opener and closer muscles in the asymmetric claws of A. californiensis were investigated using sarcomere length measurements and histochemical techniques. In the smaller pincer claw 2 types of muscle fibers are regionally distributed within the single closer muscle. A central band of fibers have short (2.5 .mu.m) sarcomeres and high myofibrillar ATPase activity. Intermediate-type fibers have smaller diameters, sarcomeres 8.5-9 .mu.m in length and low myofibrillar ATPase activity. The snapper close muscle, by contrast, is composed of fibers with long (11-14 .mu.m) sarcomeres and low myofibrillar ATPase activity. Opener muscle fibers in the pincer claw have shorter sarcomere lengths than their counterparts in the snapper claw.