SEATTLE POST-INTELLIGENCER

SEATTLE POST-INTELLIGENCER

http://seattlepi.nwsource.com/national/217621_fish26.html

Single gene in stickleback fish found to give it armor or speed

Scientists were able to isolate it to alter traits of offspring

Saturday, March 26, 2005

By DAVID PERLMAN

SAN FRANCISCO CHRONICLE

Consider the rapid evolution of the armor-plated threespine stickleback, a curious little fish that Stanford University biologist David Kingsley is setting out to study once more.

Kingsley and his team of graduate students and lab colleagues will haul their traps to the San Joaquin River near Fresno, Calif., on Monday and don hip waders for another round of collecting.

Their path-breaking research project is revealing how evolution can rapidly alter the structure of living organisms -- even one gene at a time.

Kingsley is a developmental biologist and a Howard Hughes Medical Institute investigator at Stanford's medical school, and he and his colleagues published a major report on their latest discovery in stickleback genetics yesterday in the journal Science.

But they're already set to move on, seeking still more discoveries.

Sticklebacks, only 2 to 3 inches long, are found in many varieties all over the world.

In the oceans, their bodies are covered with tough, bony, armorlike plates, while in freshwater environments, their bodies are smooth and lack all or nearly all the plates.

The fish have long been a favorite model for evolutionary biologists because some varieties have evolved relatively recently, descended from original ocean-living populations that got trapped in freshwater lakes at the end of the last ice age, some 10,000 years ago.

In evolution, that's fast, indeed.

What Kingsley and his colleagues have found most recently, according to yesterday's report in Science, is this:

A single change in a single gene has determined that the oceangoing stickleback's body gets covered with the 35 armor plates that protect it from the fierce teeth of saltwater predators, while its freshwater cousins have evolved with little or no armor -- apparently freeing it to swim swiftly and thereby to escape different kinds of fast predators.

"It seems that evolution can determine with a single gene whether it's better to be heavily armored and slow, or lightly armored and fast," Kingsley said in an interview Thursday.

In fact, he said, when he and his colleagues injected the gene that controls armor plating into the eggs of wild sticklebacks naturally free of armor, their offspring emerge well-endowed with armor plating -- and can even pass that trait on to their descendants.

The same intriguing example of rapid genetic evolution holds true wherever sticklebacks are found.

Kingsley's group has studied and crossbred the wild fish -- both armored and unarmored -- that are sent to his lab by colleagues from oceans and ponds and rivers all over the world.

For the first time, Kingsley and his Stanford group are reporting, they were able to isolate and identify the gene that controls armor plating in the fish and have determined its DNA sequence.

It is a gene called Eda, they found.

In humans, the gene causes a non-fatal hereditary disorder called ectodermal dysplasia, which can cause defects in the skin, hair, teeth and other parts of the body.

Only a year ago, the Stanford researchers reported in the journal Nature that they had discovered a similar example of rapid evolution in sticklebacks -- also triggered by a single gene.

That one has caused some populations of freshwater threespine sticklebacks to completely lose their three sharp-pointed pelvic fins.

Now Kingsley's group is preparing to trap hundreds more of the fish.

Its aim: to compare the teeth of the different varieties of sticklebacks to see how evolution has changed them and to discover the gene or genes responsible for the changes.