Papa salmon plus mama salmon equals ... baby trout? Japanese
researchers put a new spin on surrogate parenting as they engineered
one fish species to produce another, in a quest to preserve
endangered fish.
Idaho scientists begin the next big step next month, trying to
produce a type of salmon highly endangered in that 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 U.S. government-funded sockeye project.
The Tokyo University inventors dubbed their method 'surrogate
broodstocking.' They injected newly hatched 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. Captive breeding of endangered
fish is difficult, and attempts to freeze fish eggs for posterity so
far have failed.
'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, in particular, the sturgeons and paddlefish,'
he added. 'We have a lot of species of fish around the world that
are really in danger of becoming extinct.'
The Japanese researchers' ultimate goal: Boost the rapidly dwindling
population of bluefin tuna, a species prized in a country famed for
its tuna appetite.
'We need to rescue them somehow,' said Goro Yoshizaki, a Tokyo
University marine scientist who is leading the research.
First, Yoshizaki's 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, called milt.
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 were still primitive enough to switch gears from
sperm-producers to egg-producers when they wound up inside female
organs, explained Idaho's Cloud.
Then Yoshizaki used the salmon-grown trout sperm to fertilize 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.
Those first experiments, funded by a Japanese research institute,
used still fairly plentiful species to develop the technique. 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.
In Japan, Yoshizaki is focused on bluefin tuna, noting that
standard 'marine ranching' techniques are difficult for tuna that
can reach man-size.
He has begun experiments into how to produce baby tuna from
mackerel, which are nearly a thousand times smaller than adult tuna.
If it works, 'we can save space, cost and labor,' he predicted in an
e-mail interview.
researchers put a new spin on surrogate parenting as they engineered
one fish species to produce another, in a quest to preserve
endangered fish.
Idaho scientists begin the next big step next month, trying to
produce a type of salmon highly endangered in that 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 U.S. government-funded sockeye project.
The Tokyo University inventors dubbed their method 'surrogate
broodstocking.' They injected newly hatched 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. Captive breeding of endangered
fish is difficult, and attempts to freeze fish eggs for posterity so
far have failed.
'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, in particular, the sturgeons and paddlefish,'
he added. 'We have a lot of species of fish around the world that
are really in danger of becoming extinct.'
The Japanese researchers' ultimate goal: Boost the rapidly dwindling
population of bluefin tuna, a species prized in a country famed for
its tuna appetite.
'We need to rescue them somehow,' said Goro Yoshizaki, a Tokyo
University marine scientist who is leading the research.
First, Yoshizaki's 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, called milt.
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 were still primitive enough to switch gears from
sperm-producers to egg-producers when they wound up inside female
organs, explained Idaho's Cloud.
Then Yoshizaki used the salmon-grown trout sperm to fertilize 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.
Those first experiments, funded by a Japanese research institute,
used still fairly plentiful species to develop the technique. 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.
In Japan, Yoshizaki is focused on bluefin tuna, noting that
standard 'marine ranching' techniques are difficult for tuna that
can reach man-size.
He has begun experiments into how to produce baby tuna from
mackerel, which are nearly a thousand times smaller than adult tuna.
If it works, 'we can save space, cost and labor,' he predicted in an
e-mail interview.
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