Giant danio could prove key for fish farming – Fishupdate.com

Giant danio could prove key for fish farming Published:  29 November, 2006

TWO fish that share much in common genetically, appear to have markedly different abilities to grow, a finding that could provide a new way to research such disparate areas as muscle wasting disease and fish farming, a new study shows.

The study, published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, finds that the giant danio, unlike its cousin the zebrafish, appears to have the ability to recruit new muscle throughout its life. Humans have the same ability before birth, but mostly lose it afterwards.

Because the zebrafish and giant danio are closely related, and the zebrafish’s genome has already been mapped, scientists hope they can more easily identify the genetic keys to the difference in growth potential between them. According to co-author Peggy R. Biga, “I don’t think there will be a major genomic difference between them. I believe it will be easy to define the difference.”

Zebrafish and giant danios, members of the minnow family, are easy to raise and are popular inhabitants of home aquariums. They are native to the warm waters around India and some other areas of southern Asia. Although both are small, the danio is a giant among minnows, growing to a maximum of six inches. The zebrafish, in contrast, grows to about two inches.

The zebrafish has been a staple of genetic research because it is easy to raise and maintain. But the fish is too tiny for physiological research. So the researchers were interested in finding a close zebrafish relative to allow them to do physiological research while drawing on the knowledge base of the zebrafish genome.

The researchers saw the giant danio as the physiological model and began a series of experiments on differences in muscle growth between the fish. In this two-phased experiment, they discovered that the giant danio can keep growing even into adulthood, but the zebrafish stops growing. The giant danio can get bigger because it exhibits a type of muscle growth that is different from the zebrafish.

“One of these species either lost or gained the ability to continuously grow, but most likely, the zebrafish lost it”, co-author Peggy R. Biga, explained. Because genes are the key, the zebrafish’s mapped genome will be invaluable in finding what is different about the danio’s genetic pathways that allow it to keep growing.

There is also an application to fish farming. “If we understood how fish grow, we could figure out strategies for enhancing the growth of farmed fish, such as Atlantic salmon and decrease the time to get to market size. “The more we understand about growth, the more likely we can come up with acceptable ways to enhance it,” she said.

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