Summary
Finlets are small non-retractable fins located on the dorsal and ventral margins of the body between the second dorsal and anal fins and the tail of scombrid fishes. The morphology of the finlets, and finlet kinematics during swimming in a flow tank at speeds of 0.8-3. 0 fork lengths s(−1), were examined in the chub mackerel Scomber japonicus. Functionally, S. japonicus has five dorsal and anal triangular finlets (the fifth finlet is a pair of finlets acting in concert). Slips of muscle that insert onto the base of each finlet indicate the potential for active movement. In animals of similar mass, finlet length and area increased posteriorly. Finlet length, height and area show positive allometry in animals from 45 to 279 g body mass. Summed finlet area was approximately 15 % of caudal fin area. During steady swimming, the finlets typically oscillated symmetrically in the horizontal and vertical planes. Finlet excursions in the x, y and z directions ranged from 1 to 5 mm, increased posteriorly and were independent of speed. The timing of the maximum amplitude of oscillation was phased posteriorly; the phase lag of the maximum amplitude of oscillation was independent of speed. During some periods of gliding, a finlet occasionally moved independently of the body and the other finlets, which indicated active control of finlet movement. The angle of attack of the finlets averaged approximately 0 degrees over a tailbeat, indicating no net contribution to thrust production via classical lift-based mechanisms. However, the timing of finlet movement relative to that of the tail suggests that more posterior finlets may direct some flow longitudinally as the tail decelerates and thereby contribute flow to the developing caudal fin vortex.
- © 2000 by Company of Biologists
Article navigation
Related articles
Cited by...
More in this TOC section
Similar articles
Other journals from The Company of Biologists
Meet the Editors at SICB Virtual 2021
Reserve your place to join some of the journal editors, including Editor-in-Chief Craig Franklin, at our Meet the Editor session on 17 February at 2pm (EST). Don’t forget to view our SICB Subject Collection, featuring relevant JEB papers relating to some of the symposia sessions.
2020 at The Company of Biologists
Despite 2020's challenges, we were able to bring a number of long-term projects and new ventures to fruition. As we enter a new year, join us as we reflect on the triumphs of the last 12 months.
The Big Biology podcast
JEB author Christine Cooper talks to Big Biology about her research. In this fascinating JEB sponsored podcast she tells us how tough zebra finches adjust their physiology to cope with extreme climate events.
Developmental and reproductive physiology of small mammals at high altitude
Cayleih Robertson and Kathryn Wilsterman focus on high-altitude populations of the North American deer mouse in their review of the challenges and evolutionary innovations of pregnant and nursing small mammals at high altitude.
Read & Publish participation extends worldwide
“Being able to publish Open Access articles free of charge means that my article gets maximum exposure and has maximum impact, and that all my peers can read it regardless of the agreements that their universities have with publishers.”
Professor Roi Holzman (Tel Aviv University) shares his experience of publishing Open Access as part of our growing Read & Publish initiative. We now have over 60 institutions in 12 countries taking part – find out more and view our full list of participating institutions.