Record-breaking wing muscles attract mates
Male manakins have the fastest limb muscles recorded, which they use to perform mating dances.
Many animals court mates and fight with rivals by performing physically elaborate and showy displays. From male fiddler crabs waving their claws to attract females, to the leaping dances of whooping cranes, these displays often involve remarkably fast limb movements. However, in many cases it is puzzling how animals can perform these behaviors, because the muscles that move the limbs are often geared to produce strength for walking, running or flying, and not speed. Indeed, decades of research in animal physiology has confirmed that limb-moving muscles can contract with either great strength or great speed, but never both.
A small group of tropical birds called manakins produce different types of courtship displays, including some in which the wings are moved extremely rapidly. To date, nobody has examined if or how the limb muscles can generate such superfast movements.
Matthew Fuxjager and colleagues now show that, in two species of manakins that produce rapid wing movements as part of their courtship displays, one of the main wing muscles has evolved to move the wings at superfast speeds. In fact, this muscle can move the wing at speeds that are more than twice as fast as those required for these birds to fly, and appears to be the fastest limb muscle on record for any animal with a backbone. Fuxjager and colleagues also show that the manakins’ other wing muscles are no different from other birds, and suggest that these muscles are preserved to produce the strength needed for flying.
Further studies could now explore how this one muscle can create such superfast wing movements and whether male hormones, like testosterone, play a role in regulating the muscle’s speed.
To find out more
Read the eLife research paper on which this eLife digest is based: “Select forelimb muscles have evolved superfast contractile speed to support acrobatic social displays” (April 12, 2016).
