Ocean Watch
By Susan Scott
Zebrafish can regrow
parts of their heartsI recently read about a study showing that zebrafish can regenerate missing parts of their hearts. Researchers anesthetized 10 of these 1- to 2-inch-long fish, removed 20 percent of their hearts and then returned the little patients to their tanks.
Eight fish survived this radical surgery and in 10 days began swimming normally. Two months later, scientists examined the hearts of these test fish and found they had totally regrown the removed parts with almost no scarring.
Although many questions remain, this discovery is exciting to those in the field of regenerative medicine.
But I had my own question about this study: What the heck is a zebrafish?
A zebrafish, I discovered, is a black-and-silver striped fish sold in pet shops for freshwater aquariums. Zebrafish, also called Brachydanio rerio, are natives of India but are easy to breed. U.S. supply houses raise them by the bucketful for home aquariums and research labs.
Aquarium owners like zebrafish because they are pretty, hardy and inexpensive. These fish are good starters for someone setting up a first aquarium.
But besides making good pets, these little fish are extremely useful as research animals and teaching aids.
Because zebrafish eggs are transparent, teachers use this species to study biology. Students can learn how structures and functions change during embryo development simply by watching.
Researchers like working with zebrafish for several reasons. One is that these fish carry about 85 percent of the genes present in humans. Studies using these fish may, therefore, help create treatments for human ailments.
Zebrafish genes are also famous among scientists for being easy to mutate or delete, thus making those gene functions easier to analyze. You can imagine the types of mutations induced by some of the names given the resulting fish: speed bump, zombie, ogre, lost-a-fin, piggy tail, snow white, sleepy, Cyclops and Van Gogh.
One zebrafish was named Dracula because it died when exposed to light. Scientists learned that an enzyme deficiency made the fish's red blood cells so sensitive to light, they popped. Studies on the Dracula zebrafish may help humans who have similar enzyme deficiencies, called porphyrias.
One researcher is breeding zebrafish with fluorescent organs. These see-through fish can have bright green nerves, blood, pancreas or any other organ someone wants to study.
Other scientists have bred zebrafish that can detect water pollutants by glowing a certain color.
To create such radiant fish, biologists extracted fluorescent genes from jellyfish and injected them into zebrafish eggs. In the presence of certain substances, such as heavy metals, toxins or other pollutants for which the color has been specifically aimed, the fish glow red or green.
Although only those two colors have been produced so far, researchers can add up to five colors to a zebrafish, a different color for each given pollutant.
After learning all this, I went to a pet store to check out these versatile fish, also called danio in the shops. Now, I not only know about zebrafish hearts, genes, eggs and guts, I have four entertaining me in a small tank on my desk.
I hope everyone finds some fun in their work over the holidays.
Marine science writer Susan Scott can be reached at http://www.susanscott.net.
