Summary
To learn about muscle function in two species of tuna (yellowfin Thunnus albacares and skipjack Katsuwonus pelamis), a series of electromyogram (EMG) electrodes was implanted down the length of the body in the internal red (aerobic) muscle. Additionally, a buckle force transducer was fitted around the deep caudal tendons on the same side of the peduncle as the electrodes. Recordings of muscle activity and caudal tendon forces were made while the fish swam over a range of steady, sustainable cruising speeds in a large water tunnel treadmill. In both species, the onset of red muscle activation proceeds sequentially in a rostro-caudal direction, while the offset (or deactivation) is nearly simultaneous at all sites, so that EMG burst duration decreases towards the tail. Muscle duty cycle at each location remains a constant proportion of the tailbeat period (T), independent of swimming speed, and peak force is registered in the tail tendons just as all ipsilateral muscle deactivates. Mean duty cycles in skipjack are longer than those in yellowfin. In yellowfin red muscle, there is complete segregation of contralateral activity, while in skipjack there is slight overlap. In both species, all internal red muscle on one side is active simultaneously for part of each cycle, lasting 0.18T in yellowfin and 0.11T in skipjack. (Across the distance encompassing the majority of the red muscle mass, 0.35-0.65L, where L is fork length, the duration is 0.25T in both species.) When red muscle activation patterns were compared across a variety of fish species, it became apparent that the EMG patterns grade in a progression that parallels the kinematic spectrum of swimming modes from anguilliform to thunniform. The tuna EMG pattern, underlying the thunniform swimming mode, culminates this progression, exhibiting an activation pattern at the extreme opposite end of the spectrum from the anguilliform mode.
- © 1999 by Company of Biologists
REFERENCES
Article navigation
Related articles
Cited by...
More in this TOC section
Similar articles
Other journals from The Company of Biologists
Predicting the Future: Species Survival in a Changing World
Read our new special issue exploring the significant role of experimental biology in assessing and predicting the susceptibility or resilience of species to future, human-induced environmental change.
Adam Hardy wins the 2020 Journal of Experimental Biology Outstanding Paper Prize
Congratulations to winner Adam Hardy for his work showing that goby fins are as touch sensitive as primate fingertips. Read Adam’s paper and find out more about the 12 papers nominated for the award.
Stark trade-offs and elegant solutions in arthropod visual systems
Many elegant eye specializations that evolved in response to visual challenges continue to be discovered. A new Review by Meece et al. summarises exciting solutions evolved by insects and other arthropods in response to specific visual challenges.
Head bobbing gives pigeons a sense of perspective
Pigeons might look goofy with their head-bobbing walk, but it turns out that the ungainly head manoeuvre allows the birds to judge distance.