I'm always amazed by the imagination of scientists. Can you believe that Japanese researchers have created an animal species from another one? The Independent in the UK reports that "salmon gives birth to trout in scientific leap that gives hope to endangered fish." The scientists injected "germ cells from young trout into young salmon. Thirty days later, when the salmon became sexually mature, they produced sperm and eggs of trout. Only 0.4 percent of the offspring were healthy trout while the other 'children' were hybrids which died at a very young age. This doesn't discourage the researchers. Now they want to use mackerels to produce bluefin tuna, a fish loved by Japanese sushi lovers, but poised to extinction at current fishing rates. Amazing!
Here is the beginning of the Independent article which explains what the scientists did.
Biology textbooks will never quite be the same again. Scientists have altered the reproductive organs of salmon so that they produce trout offspring.
A "germ" tissue from young trout was put into young salmon so that when the salmon became sexually mature they produced the sperm and eggs of trout. In a study published today in the journal Nature, the researchers report that they have successfully used the technique to breed healthy rainbow trout from salmon parents.
The scientists, led by Yutaka Takeuchi of the Tokyo University of Marine Science and Technology, said that the development could help many of the world's endangered species of fish. Dr Takeuchi said tissue transplants from one endangered species to a related but more common species that is easier to rear in captivity could help to boost the wild populations of threatened or commercially valuable fish.
What is even more puzzling is that the researchers worked with North American rainbow trout and masu salmon, which is only found in east Asia.
The technique relies on transplants of "primordial germ cells", which are the specialised tissues of embryonic fish that eventually develop into the gonads, the sex organs of adults that produce the sperm and eggs. Dr Takeuchi and his colleagues took primordial germ cells from an embryonic North American rainbow trout and transplanted them into the embryos of the masu salmon, which is only found in east Asia. Although the two species are related -- they both belong to a group known as the salmonids -- they have been separated by at least eight million years of evolutionary history.
Now they want to use the same techniques with other species, as reports Nature Online in "Salmon give birth to trout."
If the technique does work in other species, it could be a boon to sushi lovers, Yoshizaki hopes. Bluefin tuna is a key ingredient in many sushi recipes, but because they weigh up to 500 kilograms, adult fish are difficult and expensive to house on fish farms. If the related, but much smaller, mackerel can be made to produce tuna eggs and sperm, Yoshizaki suggests, the young tuna could be reared in huge numbers and then released into the sea to be caught by local fishermen.
Other scientists are skeptical, as reports BBC News Online in "Cell swap could help conservation."
Professor Norman MacLean from Southampton University, a leading UK authority on fish genetics and genomics, said the technique would be difficult to master.
"First you have to locate what are called the genital ridges in the trout embryo in order to extract the germ cells, then micro-inject the cells into another embryo" he told the BBC.
However Professor MacLean believes there might be commercial applications.
"The obvious one is the sturgeon, which only become reproductively mature around the age of ten," he said, "so perhaps you could have them reared by another species which develops much faster."
The research work has been published by Nature in its August 5, 2004 issue. Here is a link to the abstract of the paper named "Surrogate broodstock produces salmonids."
A worldwide decline in the number of wild salmonids calls for strategies to restore endangered populations. Here we show that germ cells can be transplanted between two different salmonid species, with the subsequent production of xenogenic, donor-derived offspring. This pioneering xenotransplantation technology may eventually find applications in facilitating the production of commercially valuable fish, as well as in species conservation.
These scientists may have lots of imagination, but I'm not sure that I like some of their discoveries.
Sources: The Independent, August 5, 2004; Michael Hopkin, Nature Online, August 4, 2004; Richard Black, BBC News Online, August 5, 2004; Nature 430, 629 - 630, August 5, 2004
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