The fast-acting, synchronous "remotor" muscle of the lobster second antenna was examined by light and electron microscopy and was found to have a more profuse sarcoplasmic reticulum (SR) than any other muscle known. Myofibrils are widely separated from one another and occupy only about one-fourth of the volume of the muscle; most of the remaining volume is taken up by the SR, which resembles the smooth-surfaced reticulum of steroid-secreting cells. Dense granules (0.03–0.1 µ in diameter) are scattered through the reticulum. T-tubules penetrate into the fibers and form dyads along the A bands of myofibrils; however, ferritin-labeling experiments show that the volume of the T-system is very small compared with that of the SR. Myofibrils are ∼0.5 µ x 1.0 µ in cross section and consist of thick filaments, which appear tubular except at the M region, and thin filaments, which are situated midway between neighboring thick filaments. The ratio of thin to thick filaments is 3:1. The extreme development of the SR in this muscle is discussed in relation to the exceedingly short duration of the contraction-relaxation cycle.
Article| August 01 1969
SARCOPLASMIC RETICULUM OF AN UNUSUALLY FAST-ACTING CRUSTACEAN MUSCLE
From the Departments of Physiology and Rehabilitation Medicine, New York University Medical Center, New York 10016
Received: September 20 1968
Revision Received: March 24 1969
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1969 by The Rockefeller University Press.
Jack Rosenbluth; SARCOPLASMIC RETICULUM OF AN UNUSUALLY FAST-ACTING CRUSTACEAN MUSCLE . J Cell Biol 1 August 1969; 42 (2): 534–547. doi: https://doi.org/10.1083/jcb.42.2.534
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