UF experts breed puffer fish in captivity; pet trade and genetics research could benefit
GAINESVILLE, Fla. — Spotted green puffer fish seldom reproduce in captivity, but University of Florida experts have created the first commercial breeding method reported in the United States, a move that could benefit the tropical fish industry and genetics researchers.
A UF team investigated the species at the request of producers, who hope to breed some of the estimated quarter million spotted green puffers sold annually to North American hobbyists and researchers, said Craig Watson, director of UF’s Tropical Aquaculture Laboratory in Ruskin, part of the Institute of Food and Agricultural Sciences.
“The supply has been variable and sometimes quite limited because they’re wild-collected, mostly in Thailand,” Watson said. “So this was a good species for us to investigate.”
Watson, who led the research team, will present findings today at a World Aquaculture Society meeting in Seattle.
Native to brackish waters in South and Southeast Asia, the fish grows to about six inches. When frightened, its body rapidly inflates into a spiny ball.
It has the smallest genome of any vertebrate that has been genetically sequenced, about one-tenth the size of the human genome, Watson said. Some genomics researchers use it as a model animal. But because only juveniles and adults have been available, the species had little value in fields such as embryology and genetics.
UF’s method could enable scientists to study the fish from fertilization, he said. It could also let them trace a puffer’s lineage back several generations, to study inherited traits. Other animals are used for genetics research, including the zebrafish, another popular aquarium fish, said Hugues Roest Crollius, a research scientist with the Ecole Normale Supérieure in Paris. So it’s unknown how many scientists will embrace the puffer.
“The people who jump on it will have very specific questions, when genes are expressed and where,” said Roest Crollius, who helped sequence the fish’s genome. “It will be of real interest for people who want to take advantage of the compact genome for techniques based on molecular genetics.”
An important first step, he said, is to show the fish can be used for transgenic experiments. One basic study involves adding a reporter gene — such as the gene that produces green fluorescent protein — to a specific gene sequence in a developing puffer. By observing when and where the green fluorescent protein appears, scientists can learn about the function of the puffer gene sequence they’ve targeted.
Watson hopes to see such studies performed soon. He’s secured U.S. Department of Agriculture funding to test whether the captive breeding method works in goldfish.
The method, known as ovarian lavage, is a twist on an older approach to breeding commercially valuable fish that won’t spawn naturally in captivity, Watson said.
In the standard approach, breeders inject female fish with a chemical that promotes egg development, he said. The eggs are gently removed and fertilized.
Spotted green puffers aren’t suitable for injection because they have little muscle mass and their skin is unusually elastic. So the UF team used a catheter to introduce the chemical directly to the female’s ovaries. After several trials they reached nearly 100 percent success in egg fertilization and hatching, he said.
They’ve demonstrated the method for several Florida producers, including Marty Tanner, owner of Plant City’s Aquatica Tropicals Inc.
Tanner plans to sell spotted green puffers to the pet and research markets.
“We supply zebrafish for research so this will be a good item for us,” he said. “We’re not sure of the demand for puffers but there’s never been enough supply.”
Watson said he’s investigating other species that might be bred using ovarian lavage.
One is the fire eel, an expensive aquarium fish that can’t be injected because its body is too muscular. Another is the Japanese fugu fish, a popular delicacy.