Slow muscle function of Pacific bonito (Sarda chiliensis) during steady swimming

• Main Authors: D. J. Ellerby, J. D. Altringham, T. Williams, Leeds Ls Jt
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2000
• Subjects: Key words; swimming; Pacific bonito; Sarda chiliensis; Pacific; Anguilla anguilla
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.383.7043; http://www.tunaresearch.org/reprints/Slow Muscle Function of Pacific Bonito (Sarda Chilienis) Dur.pdf

intermediate between mackerel and tuna. The specialisations exhibited by tuna are present in the bonito, but to a lesser degree. Slow-twitch muscle strain and activity patterns were determined during steady swimming (tailbeat frequency 1.2–3.2 Hz) at four locations on the body of Sarda chiliensis using sonomicrometry and electromyography. Both strain and the phase of electromygraphic activity were independent of tailbeat frequency. The strain of superficial slow-twitch muscle increased from ±3.1 % l0 at 0.35FL to ±5.8 % l0 at 0.65FL, where l0 is muscle resting length and FL is the body length from snout to tail fork. Between 0.35 and 0.65FL, there was a negative phase shift of 16 ° in the onset of electromygraphic activity in superficial slow-twitch muscle Summary relative to the strain cycle. Muscle activity patterns are comparable with those of tuna. At 0.58FL, the onset of activity in deep slow-twitch muscle was approximately synchronous with the onset of activity in superficial muscle in the same myotome at 0.65FL. The distribution of slowtwitch muscle along the body of Sarda chiliensis and four additional fish species, Anguilla anguilla, Oncorhynchus mykiss, Scomber scombrus and Thunnus albacares, was also measured. Slow-twitch muscle appears to become more concentrated at approximately 0.5FL as swimming kinematics become more thunniform.