Rockin’ Horses

The odd form and function of seahorses captivates researcher Miriam Ashley-Ross.

ooking for a critter whose physiology and locomotion mechanics differ radically from the standards of its species? Look no farther than the seahorse.
It’s a fish, but you’d never know it by observing it. Instead of a smooth, streamlined profile with scales, it has an exoskeleton with armored plates and spines. Its head is upright and bent over. It moves not by swishing a tail fin (which it lacks) languidly, but by oscillating its dorsal and pectoral fins 30 times per second in the viscous medium of water. “They’re interesting little animals,” notes Miriam Ashley-Ross, an ardent admirer. “You have to admit, they’re pretty odd-looking.”

It’s that very oddity that has attracted the research attention of Ashley-Ross, an assistant professor of biology. She describes herself as a “functional morphologist”—one who studies the relationship between form and function in physiology. And what better subject for study than a creature whose body and means of motion depart drastically from its species? Her motivation, though, is not mere curiosity about one of nature’s apparent aberrations. Her work is contributing to our general understanding of muscle itself and how it can be designed for specialized tasks.

Ashley-Ross, who joined the University’s faculty in 1997, began studying the seahorse in 1995 as a doctoral student at the University of California-Irvine. She examines its muscle by placing samples in petri dishes, where the tissue can survive for up to 12 hours if cared for properly. The morphologist explains that in muscle, three elements, each with a different function, compete for space. One element produces force, another provides sustained energy, and the third enables rapid contraction. In any given muscle, each element can be emphasized at the expense of the others.

Because to propel itself the seahorse’s dorsal muscle must contract so rapidly, the muscular elements producing force and providing sustained energy “take a hit,” as Ashley-Ross describes it. Put simply, it can’t move very fast or for very long.

So how does it survive in aquatic environments teeming with voracious beasts? By looking funny. “They rely a great deal on being cryptic—by looking like a bit of flotsam and jetsam that predators can’t see or aren’t interested in,” Ashley-Ross explains.

The animal kingdom—including the human realm—is rife with examples of specialized muscular configurations, all with a functional purpose. The fastest land animal, the cheetah, is equipped with very long limbs, and its shoulder blade is connected to its ribcage not by a rigid clavicle, as ours is, but by a kind of muscular harness. It’s built for short bursts of speed to close in quickly on a kill, but not for endurance. Conversely, as we humans evolved from quadrupedal to bipedal creatures, our spines became curved and our pelvises were restructured completely. “We’re built,” says Ashley-Ross, “for covering long distances at not very great speeds.”

Like most aspiring college professors, Ashley-Ross applied to a lot of schools coming out of graduate school. Out of “sheer luck,” she says, she landed at a place that values both research and teaching, which she also enjoys. Four undergraduates work in her lab. Kate Williams (’03) studies the hind limbs of salamanders to learn how muscle fiber types change with metamorphosis and training. Rebecca Lundin (’03) is describing the kinematics, or patterns of movement, of newts walking on treadmills. Brett Bechtel (’03) is charting the kinematics of newts as they transition from land to water. And Garick Hill (’02) is observing the jaws and heads of newts move as they feed.

– David Fyten