Jahromi S S, Govind C K
Cell Tissue Res. 1976 Feb 12;166(2):159-66. doi: 10.1007/BF00227037.
The physiological and ultrastructural properties of muscle fiber.s comprising three motor units in the gastric mill of blue crabs are described. In their contractile properties muscle fibers in all motor units are similar and resemble the slow type fibers in crustacean limb muscles. The majority of fibers generate large excitatory post-synaptic potentials which do not facilitate strongly. Structurally two types of fibers are found. The one type has long sarcomeres (greater than 6 mum), thin to thick myofilament ratios of 5-6:1 and diads located near the ends of the A-band. The other type has shorter sarcomeres (less than 6 mum), thin to thick myofilament ratios of 3:1 and diads located at mid sarcomere level. Both types of fibers occur within a single motor unit and this differs from the vertebrate situation. Furthermore, the finding of fibers with a low thin to thick myofilament ratio of 3:1 demonstrates that they are not exclusive to fast type crustacean muscle but also occur in slow stomach muscles.
本文描述了青蟹胃磨中三个运动单位所含肌纤维的生理和超微结构特性。在收缩特性方面，所有运动单位中的肌纤维相似，类似于甲壳类动物肢体肌肉中的慢肌纤维。大多数纤维产生大的兴奋性突触后电位，且不易产生强直增强。在结构上发现了两种类型的纤维。一种类型的肌节长（大于6μm），细肌丝与粗肌丝的比例为5-6:1，二联体位于A带末端附近。另一种类型的肌节较短（小于6μm），细肌丝与粗肌丝的比例为3:1，二联体位于肌节中部水平。两种类型的纤维都存在于单个运动单位中，这与脊椎动物的情况不同。此外，细肌丝与粗肌丝比例低至3:1的纤维的发现表明，它们并非甲壳类快肌所特有，也存在于慢肌胃中。
