New Technology - Birth by Proxy ??!!!


Written on Sunday, September 16, 2007 by Gemini

In path-breaking science, researchers have engineered a salmon to reproduce trout; conservationists laud the technology, saying it will help endangered species...

Papa salmon plus mama salmon equals... baby trout? Japanese researchers have put a new spin on surrogate parenting as they engineered one fish species to produce another, in a quest to preserve endangered fish.

Taking it from there, scientists in the US begin the next big step. Next month, they will try to produce a type of salmon highly endangered in its Idaho state: the sockeye – this time using more plentiful trout as surrogate parents.

The new method is “one of the best things that has happened in a long time in bringing something new into conservation biology,” said University of Idaho zoology professor Joseph Cloud, who is leading the US government-funded sockeye project. The Tokyo University inventors, in a method they call “surrogate broodstocking,” injected newlyhatched but sterile Asian masu salmon with sperm-growing cells from rainbow trout – and watched the salmon grow up to produce trout.

The striking success, published in Friday’s edition of the journal Science, is capturing the attention of conservation specialists, who say new techniques are badly needed. “They showed nicely that... they produced the fish they were shooting for,” said John Waldman, a fisheries biologist at Queens College in New York. “Future work should look to expand this approach to other fishes in need of conservation. We have a lot of species of fish around the world that are really in danger of becoming extinct.”How the Japanese did it?

First, Tokyo University marine scientist Goro Yoshizaki and his team started with “salmonids,” a family that includes both salmon and trout, and one of concern to biologists because several species are endangered or extinct. Initial attempts to transplant sperm-producing cells into normal masu salmon mostly produced hybrids of the two species that didn’t survive. This time, Yoshizaki engineered salmon to be sterile. He then injected newly hatched salmon with stem cells destined to grow into sperm that he had culled from male rainbow trout.

Once they were grown, 10 of 29 male salmon who got the injections produced trout sperm.Here’s the bigger surprise: Injecting the male cells into female salmon sometimes worked, too, prompting five female salmon to ovulate trout eggs. That’s a scientific first, Yoshizaki said.The stem cells, it seems, were still primitive enough to switch gears from sperm-producers to egg-producers when they wound up inside female organs.

Then Yoshizaki used the salmon-grown trout sperm to fertilise both wild trout eggs and the salmon-grown trout eggs. DNA testing confirmed that all of the dozens of resulting baby fish were pure trout, he reported. Moreover, those new trout grew up able to reproduce. Now comes Idaho’s attempt to prove if the method is really useful in trying to produce the endangered sockeye salmon. Last January, Yoshizaki helped University of Idaho scientists collect and freeze immature sperm tissue from young sockeye salmon being raised at a state-run hatchery.

Next month, he’ll be back to help Cloud thaw the tissue and implant it into sterile rainbow trout. If they’re successful, this time around, papa trout plus mama trout will equal baby salmon.

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