Date: April 12, 2016
Studies in a group of tropical birds have revealed one of the fastest limb muscles on record for any animal with a backbone. The muscle, which can move the wing at more than twice the speeds required for flying, has evolved in association with extravagant courtship displays that involve rapid limb movements, according to a paper to be published in the journal eLife.
The 'superfast' wing movements of male red-capped and golden-crowned manakins are undetectable to the human eye, and are about six to eight times faster than the 8-hertz (Hz) speed at which a sprinter, such as Olympian athlete Usain Bolt, moves their legs through the air in a 100-metre run.
"The discovery of the superfast wing muscle in these birds paves the way for further studies into what has to change, or what can change, in a muscle to make it drive faster movements," says first author Matthew Fuxjager, from Wake Forest University.
"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."
Many different species perform rapid limb movements as part of their courtship displays, from certain birds running across lake surfaces, to the unusual boxing displays of hares in March.
However, because muscle performance is limited by trade-offs between speed and force, it is unclear how animals develop the ability to generate both the swift movements involved in showy physical displays and the force needed to drive these movements.