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A Multifunction Muscle in Squid. | LitMetric

AI Article Synopsis

  • Some striated muscles in animals have multiple functions during movement, acting as motors, brakes, or struts.
  • Researchers discovered a multifunctional muscle in cephalopods, specifically the nuchal retractor muscle, which has two types of fibers (MR and MP) responsible for different actions during locomotion.
  • The study findings indicate that the nuchal retractor muscle assists in various roles such as retracting the head, stabilizing it during direction changes, and supporting rapid extensions post-escape jet, highlighting that multifunctionality isn't limited to animals with complex skeletal systems.

Article Abstract

Some striated muscles are multifunctional; they serve several different roles during locomotion and movement, including acting as motors, brakes, struts, or springs. The few multifunctional muscles that have been reported occur in the cross-striated muscles of animals with complex, jointed, skeletal support systems. In the comparatively simple muscular system of a cephalopod mollusc, we identified an obliquely striated muscle, the nuchal retractor muscle, which appears to be multifunctional. The nuchal retractor is composed of two different fiber types, mitochondria-rich (MR) and mitochondria-poor (MP) fibers; shortening of these fibers retracts the head toward the mantle. Synchronized measurements of head movement (as a proxy for nuchal retractor length) and muscle activation revealed that, while the MP nuchal retractor muscle fibers were activated only for head retractions that occurred during escape jet locomotion, the MR fibers were activated 1) as the head retracted during escape jets and a few jets used during slow swimming, 2) during brief periods of head stasis as the animal changed swimming direction, and 3) during the rapid head extensions that followed an escape jet. Our results suggest that the nuchal retractor muscle may function as a motor, a brake, and, occasionally, a strut. More broadly, our findings suggest that multifunctionality is not restricted to cross-striated fibers or to the muscles of animals with jointed skeletal support systems.

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Source
http://dx.doi.org/10.1086/691070DOI Listing

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