Sperm Transplant Between Fish May Preserve Endangered Species

JAPAN - Transplanting reproductive cells between fish may help preserve endangered species or resurrect extinct ones, scientists in Japan say.

Researchers at Tokyo University of Marine Science and Technology injected immature sperm-creating cells from rainbow trout into salmon embryos with abnormal chromosomes to produce normal trout with healthy offspring. They also froze and thawed reproductive cells, known as spermatogonia, as a way to store genetic material of endangered fish.

One objective is building "a kind of spermatogonia bank of various fish species," said Goro Yoshizaki, who participated in the research, in a telephone interview yesterday. Transplanting the stored cells may enable scientists to revive species that become extinct, he said.

Habitat destruction, over-fishing and the introduction of farmed fish to wild populations have caused some species in the US and Japan to dwindle, including bull trout, golden trout and gila trout, Yoshizaki said. The Tokyo researchers are collaborating with the US National Oceanic and Atmospheric Administration to freeze sperm from a population of endangered sockeye salmon from Idaho, he said.

The transplant technique, reported in the journal Science today, is being use to produce bluefin tuna, prized in Japan for sushi and sashimi dishes.

Rather than farming the tuna, which weigh as much as 600 kilograms (1,320 pounds), Yoshizaki is implanting their reproductive cells in mackerel, which are about 1,000 times smaller and can be farmed in smaller facilities, he said.

"If I take spermatogonia from tuna and transplant it into mackerel, that surrogated mackerel can produce tuna egg and sperm,'' Yoshizaki said. "Then we could save a lot of cost and space and labor for tuna seed production.''

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Sperm Transplant Between Fish May Preserve Endangered Species