Recruitment patterns and contractile properties of fast muscle-fibers isolated from rostral and caudal myotomes of the short-horned sculpin

Johnston, Ian A., Franklin, Craig E. and Johnson, Timothy P. (1993) Recruitment patterns and contractile properties of fast muscle-fibers isolated from rostral and caudal myotomes of the short-horned sculpin. Journal of Experimental Biology, 185 251-265.

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Author Johnston, Ian A.
Franklin, Craig E.
Johnson, Timothy P.
Title Recruitment patterns and contractile properties of fast muscle-fibers isolated from rostral and caudal myotomes of the short-horned sculpin
Journal name Journal of Experimental Biology   Check publisher's open access policy
ISSN 0022-0949
Publication date 1993-12
Sub-type Article (original research)
Open Access Status File (Publisher version)
Volume 185
Start page 251
End page 265
Total pages 15
Place of publication Cambridge, United Kingdom
Publisher The Company of Biologists
Language eng
Formatted abstract
Muscle action during swimming and the contractile properties of isolated muscle fibres were studied in the short-horned sculpin Myoxocephalus scorpius at 5˚C. Semi-steady swimming, startle responses and prey-capture events were filmed with a high-speed video at 200frames s-1, using fish 22–26cm in total length (L). Electromyographical (EMG) recordings, synchronised with the video, were made from fast muscle in rostral and caudal myotomes at points 0.40L and 0.80L along the body. Fast muscle fibres were first recruited at tail-beat frequencies of 3.7–4.2Hz, corresponding to a swimming speed of 1.7 L s-1. Electrical activity in the muscles occurred during 16–38% of each tail-beat cycle regardless of frequency. Muscle fibres were activated during the lengthening phase of the cycle. In caudal myotomes, the onset of the muscle activity occurred at a phase of 75–105˚ at 3.7Hz, decreasing to approximately 50˚ at frequencies greater than 4.5Hz (0˚ phase was defined as the point at which muscle fibres passed through their resting lengths in the stretch phase of the cycle; a full cycle is 360˚). Prey capture was a stereotyped behaviour consisting of a preparatory movement, a powerstroke at 7–9Hz and a glide of variable duration. The delay between the activation of muscle fibres in rostral and caudal myotomes during prey capture and startle responses was approximately 10ms. Fast muscle fibres isolated from rostral and caudal myotomes were found to have similar isometric contractile properties. Maximum tetanic stress was 220kN m-2, and half-times for force development and relaxation were approximately 50ms and 135ms respectively. Power output was measured by the ‘work loop’ technique in muscle fibres subjected to sinusoidal length changes at the range of frequencies found during swimming. Under optimal conditions of strain and stimulation, muscle fibres from rostral and caudal myotomes produced similar levels of work (3.5 J kg-1) and generated their maximum power output of 25–30 W kg-1 at the tail-beat frequencies used in swimming (4–8Hz). Progressively delaying the onset of stimulation relative to the start of the strain  cycle resulted in an initial modest increase, followed by a decline, in the work per cycle. Maximum positive work and net negative work were done at stimulus phase values of 20–50˚ and 120–140˚ respectively. The EMG and swimming studies suggest that fast muscle fibres in both rostral and caudal myotomes do net positive work under most conditions.
Keyword Swimming
Contractile properties
Duty cycle
Short-horned sculpin
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biomedical Sciences Publications
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Citation counts: TR Web of Science Citation Count  Cited 27 times in Thomson Reuters Web of Science Article | Citations
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Created: Tue, 29 Mar 2016, 17:26:40 EST by Gail Walter on behalf of Learning and Research Services (UQ Library)