Honolulu Star-Advertiser © Susan Scott
August 15, 2008
How do you repair damaged heart muscle? Which genetic mutations cause malignancies? Why does a drug effective for testicular cancer impair hearing?
The answers to these weighty questions, and more, could lie in a little fish called the zebra fish. This 1-inch-long traditional aquarium pet has become the superstar of biomedical research labs.
Zebra fish are native to the Ganges River (which flows through India and Bangladesh), where the line between marine and freshwater species sometimes blurs. Dolphins live in the Ganges, as do some pipefish and puffer fish. The zebra fish, however, is a freshwater fish.
The zebra fish, a member of the minnow family, is a remarkable animal, in the wild as well as in the lab. In its native habitat, zebra fish have had to adapt to permanent, human-made changes in their waterways.
And adapt they do. Zebra fish thrive in rice paddies where they perform the service of eating mosquito larvae. The fish also do well in silt-bottomed ponds, fast-moving streams, shallow seasonal waters and, fortunately for us, aquariums.
Home aquarists know about zebra fish because they’ve been sold for decades as pets called zebra danios. (Danio rerio is their scientific name.)
A few years ago, researchers successfully implanted bioluminescent coral and jellyfish genes into zebra fish embryos to produce fluorescent fish. The idea was to make a fish that would turn a certain color in the presence of a particular type of pollutant.
I didn’t find reports of these glow-in-the-dark fish being used that way, but I did discover they’re sold as aquarium pets. These psychedelic fish, marketed as GloFish, look stunning under ultraviolet light.
More stunning, though, are the windows zebra fish are opening in research labs.
The fish are popular as study subjects because they’re cheap, hardy, produce a lot of offspring and go from fertilization to fish in three months.
In the wild, zebra fish breed at dawn, which means they breed in the lab when the lights go on. Female zebra fish produce from 100 to 200 eggs daily depending on their diet and their male tank mates. The larger the partner, the more eggs the female lays.
The main trait that makes them model lab animals is their see-through eggs. Researchers can insert a gene, create a mutation or administer a drug into a developing embryo and watch what happens.
Under a microscope, it’s possible to see a zebra fish embryo heart pumping out red blood cells.
Researchers are also interested in zebra fish because they can regrow sections of their hearts that have been surgically removed. These fish can regrow severed fins, too.
Most of us don’t see fish as our close relatives, but zebra fish are closer than you might think. Most of their genes are the same as ours.
One minor zebra fish drawback is they eat their own eggs. Workers solve this problem with marbles. When piled on the tank floor, marbles create spaces inaccessible to voracious parents.
Since the 1990s scientists have been growing zebra fish like crazy. The University of Washington alone has about 1,500 tanks containing 500 families of these fish.
When browsing in a pet store, who would ever think those little striped fish could be responsible for relieving suffering, saving lives and giving us crucial information about ourselves?
I bought six.
