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.
Locomotion in scombrid fishes: morphology and kinematics of the finlets of the chub mackerel Scomber japonicus
J.C. Nauen, G.V. Lauder; Locomotion in scombrid fishes: morphology and kinematics of the finlets of the chub mackerel Scomber japonicus. J Exp Biol 1 August 2000; 203 (15): 2247–2259. doi: https://doi.org/10.1242/jeb.203.15.2247
Download citation file:
Advertisement
Cited by
New funding schemes for junior faculty staff

In celebration of our 100th anniversary, JEB has launched two new grants to support junior faculty staff working in animal comparative physiology and biomechanics who are within five years of setting up their first lab/research group. Check out our ECR Visiting Fellowships and Research Partnership Kickstart Travel Grants. First deadline for applications is 15 July 2023.
JEB@100: an interview with Monitoring Editor Sanjay Sane

Sanjay Sane tells us about his first experience of publishing with the journal and why he thinks JEB is going to play a key role in our understanding of the current climate crisis and its implications for biodiversity.
The Forest of Biologists

The Forest of Biologists is a biodiversity initiative created by The Company of Biologists, with support from the Woodland Trust. For every Research and Review article published in Journal of Experimental Biology a native tree is planted in a UK forest. In addition to this we are protecting and restoring ancient woodland and are dedicating these trees to our peer reviewers. Visit our virtual forest to learn more.
Celebrating 100 years of discovery

This Special Issue focuses on broad biological questions addressed through the lens of comparative biomechanics. Crosscutting through time, this series of Reviews, Commentaries and Research Articles addresses questions from the vantage points of the history of the field, today’s research, and the future of comparative biomechanics. Read the Editorial by Sheila Patek, Monica Daley and Sanjay Sane.
Centenary Review - Adaptive echolocation behavior

Cynthia F. Moss and colleagues Review the behaviours used by echolocating mammals to track and intercept moving prey, interrogate dynamic sonar scenes, and exploit visual and passive acoustic stimuli.
Lack of oxygen curtails vision in red-eared sliders

When red-eared sliders sink to the bottom of a frozen pond for winter they reduce many biological systems to minimum life support, but now Michael Ariel and colleagues show that the reptiles temporarily lose their sight due to lack of oxygen but retain hearing.