Someday athletes may carry toadfish and rattlesnake charms for good luck. Both animals have some of the fastest muscles of any vertebrate. The male toadfish (Opsanus tau) produces its mating call by contracting the muscles surrounding its gas-filled swim bladder 200 times per second. Swim bladders normally help fish maintain buoyancy, but the toadfish uses the organ primarily to whistle at passing females. Male and female western diamondback rattlesnakes (Crotalus atrox) also deserve a medal for muscle speed, as they can rattle their tails 90 times per second.
What makes these potential Olympians so fast? The contraction speed requires more than just a lot of energy, according to new findings. Although these sonic muscles work much like muscles of other animals, including humans, they perform a couple of key steps with impressive speed, say Lawrence C. Rome of the University of Pennsylvania in Philadelphia and the Marine Biological Laboratories in Woods Hole, Mass., and his colleagues.
Understanding these super achieving muscles provides clues to how different parts of all muscles work, even though the study doesn't have any immediate applications for humans, asserts Michael L. Fine of Virginia Commonwealth University in Richmond.
Most muscle cells contain a salt solution, called the myoplasm, and a storage compartment for calcium, called the sarcoplasmic reticulum. To make the muscle contract and relax, calcium goes from the sarcoplasmic reticulum to the myoplasm and back. …