Fast muscle in squid (Loligo pealei): contractile properties of a specialized muscle fibre type

• DOI: 10.1242/jeb.205.13.1907
• Publication Date: 2021-04-25T04:52:40Z
• Authors: William M. Kier; Nancy A. Curtin
• Keywords: Tentacle (botany); Myofilament; Myofibril; CrossBridge

SUMMARY The contractile properties of the transverse muscle tentacles and arms squid Loligo pealei were investigated using small fibre bundle preparations. In addition,transmission electron microscopy was used to measure length thick myofilaments two types. filament cross-striated tentacle fibres 0.81±0.08 μm (mean ± S.D, N=51) while that obliquely striated arm 7.41±0.44 (N=58). difference in types predicted result a much higher shortening velocity compared with muscle. This tested by investigating force/velocity relationship for isotonic Fitting Hill's equation results gave maximum (Vmax, intercept on axis) 15.4±1.0 L0 s-1(mean S.D., N=9) 1.5±0.2 s-1 (N=8) fibres, where is at which peak isometric force recorded. also lower tension versus For tentacle, mean tetanic during brief tetanus (0.2s) 131±56 mN mm-2 cross-sectional area N=12) observed stimulus frequency 80 Hz, whereas 468±91 mm-2(N=5) 160 Hz. length/force relationships (expressed relative L0) similar. ratio twitch 0.66 but only 0.03 fibres.