Their movements are undetectable to the human eye
A new study has revealed the fastest known limb muscles for any animal with a backbone. The record goes to a group of small and colourful tropical birds able to move their wings at a speed so staggering that the motion cannot be detected by the human eye.
These ‘superfast’ muscles are not required for flight. Rather, it is during their extravagant courtship display that these wing movements are put to good use.
But given the trade-off that exists between the speed at which a muscle can contract and the force it can exert, scientists have wondered how these birds are able to manage this impressive display.
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To address this question, a team of researchers compared the twitch speeds of forelimb muscles from wild-caught golden-collared and red-capped manakins to those of three other related species: the blue-crowned manakin, the dusky antbird, and the house wren.
"Of the species studied, the golden-collared and red-capped manakins produce exceptionally rapid wing movements as part of their acrobatic courtship displays," said first author Matthew Fuxjager, from Wake Forest University.
As Fuxjager explains, the golden-collared manakins perform 'roll-snaps', which involved hitting their wings together above the back at around 60 Hz to produce a loud mechanical sound. Red-capped manakins produce a similar sound with their 'clap' display, whereby the wings are extended slightly above the body and then quickly retracted back to the sides, at around 45 Hz.
These two species appear to have evolved superfast movements in their humeral (inner wing) muscles, but other muscles that are used in flight do not differ from those of other birds — they have been preserved to maintain the strength needed for flying.
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The authors state in the paper that this study provides evidence of “a unique evolutionary design of the forelimb muscular system that enables both rapid movement for displaying and force-generating movement for locomotion.”
And the significance of this study extends well beyond birds. As Fuxjager explains, the discovery of a superfast wing muscle in these birds could lead to future advances in our understanding of how to drive faster movements in human muscle.
"This could be important for developing therapies for motor disorders, particularly those characterized by decreases in muscle performance that result from diseases such as cancer and HIV,” said Fuxjager.
High-speed video of a golden-collared manakin performing a roll-snap display.
Credit: Barney Schlinger. Published in: Fuxjager, M.J., Longpre, K.M., Chew, J.G, Fusani, L. and Schlinger, B.A. (2013). Peripheral androgen receptors sustain the acrobatics and fine motor skill of elaborate male courtship. Endocrinology, 154: 3168-3177.
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