URI scientist's development of more muscular trout could boost commercial aquaculture

A 10-year effort by a University of Rhode Island scientist to develop transgenic rainbow trout with enhanced muscle growth has yielded fish with what have been described as six-pack abs and muscular shoulders that could provide a boost to the commercial aquaculture industry.

Terry Bradley, a URI professor of fisheries and aquaculture, said his research into the inhibition of myostatin, a protein that slows muscle growth, has obtained ''stunning results'' in the last two years, with trout growing 15 to 20 percent more muscle mass than standard fish.

''Belgian blue cattle have a natural mutation in myostatin causing a 20 to 25 percent increase in muscle mass, and mice overexpressing myostatin exhibit a two-fold increase in skeletal muscle mass. But fish have a very different mechanism of muscle growth than mammals, so we weren't certain it was going to work,'' Bradley said.

According to Bradley, the number of muscle fibers in mammals is limited after birth, but in fish, muscle fiber numbers increase throughout their lifespan. Since inhibition of myostatin increases the numbers of muscle fibers, it had been a mystery as to whether inhibiting myostatin would cause an increase in muscle growth in fish.

Bradley and a team of graduate students spent 500 hours injecting 20,000 rainbow trout eggs with various DNA types designed to inhibit myostatin. Of the eggs that hatched, 300 carried the gene that led to increased muscle growth. After two years, most exhibited a ''six-pack ab'' effect, even though fish lack standard abdominal muscles. They also have increased musculature throughout, including a prominent dorsal hump that made them look like they had muscular shoulders.

The first generation of transgenic trout were subsequently spawned, and offspring carrying the gene in all of their muscle cells have been produced. Studies are under way to determine if the fish grow at a faster rate as well.