Japanese scientists use salmon to make trout

1.00pm

LONDON - Japanese scientists have created trout whose fathers were salmon in an experiment that they say may help preserve endangered species and boost the world's fish supplies.

In a report in the science journal Nature on Wednesday, researchers at Tokyo University of Marine Science and Technology described how they transferred primordial germ cells, which can develop into either sperm or eggs, from newly hatched rainbow trout embryos to masu salmon embryos.

Thirty days after the transplant the specially marked donated cells were present in the ovaries and sperm of some of the salmon.

Trout sperm from the salmon was later used to fertilise trout eggs which produced healthy fish whose DNA fingerprints were similar to the donor trout.

"Trout offspring can be created from trout-donor germ cells transplanted into salmon," Yutaka Takeuchi and his colleagues said in the journal.

Primordial germ cells had previously been successfully transplanted from one species to another in fruit flies and birds but without producing offspring.

"If primordial germ cells isolated from endangered fishes could be cryopreserved (frozen), these cells could be converted into live fishes via our transplantation technique -- even after species are extinct in the wild," Takeuchi said in an email interview.

He added that if primordial germ cells of a big, slow-developing fish like bluefin tuna could be transplanted into smaller fish like mackerel, the surrogate mackerel could produce mature tuna eggs and sperm in a shorter time than tuna parents.

"Therefore, our technique may help to feed the world's sushi habit."

Rainbow trout and masu salmon come from different areas of the world and the two species diverged at least 8 million years ago. They also have different breeding patterns. Rainbow trout spawn several times during their lifetime but masu salmon die after their first spawning.

All of the fish that resulted from the tranplanted germ cells were healthy, according to the researchers.

- REUTERS