Salmon Give Birth to a Baby Trout, Researchers Say

Researchers at the Tokyo University of Marine Science and Technology in Japan, led by Goro Yoshizaki, have successfully made two salmon give birth to a trout. The researchers claim that their technique could help preserve rare species of fish. The same researchers have previously succeeded in injecting a male salmon with cells from closely-related trout to produce trout sperms and when the sperm were injected to trout eggs, healthy trout offspring were produced.

Nature.com reveals that the researchers' technique involves injecting a trout's early, stem-cell state of sperm called spermatagonia into salmon embryos. When the injected embryos grows into salmon, they produce trout and sperm eggs.

When the trout spermatagonia injected into a male salmon embryo, the male salmon will grow up and produce a mix of salmon and trout sperm. The same goes for the female salmon, if the female salmon embryos were injected with trout spermatagonia, when the female salmon grew up, they produced all trout eggs. In the research team's previous work, sperm from male salmon injected with an even earlier stage of sperm were used to fertilize trout eggs and only .4% of the offspring were healthy trout.

To increase the percentage, the team used salmon that have three sets of chromosomes instead of two which made the salmon sterile. When these salmon were injected with spermatagonia, the only viable sperm that the male salmon produced were from the injected cells, making them pure trout. The next step for the researchers were to use two sterile masu salmon and make them produce a healthy trout offspring.

David Penman, a fish geneticist at the University of Stirling, UK commented that the research team's technique could be very useful for storing back-up genetic material of different fish species that are under threat since spermatagonia can be easily cryopreserved. "The problem with gene-banking when you come to fish, is that it's almost impossible with eggs," Penman adds."The eggs are very big, very yolky, which makes them nearly impossible to freeze." Using Yoshizaki's technique, if it is applicable to other fish, would mean that there's no need for the eggs to be preserved since they could be made at a later date in a surrogate fish.

Penman was amazed to see that the researchers injected spermatagonia and got eggs. He said that that the fish were very plastic. Though the technique could be very useful to preserve endangered fish, Penman said that some species would be harder to work with if researchers don't have a closely related recipient for a surrogate.

The results of Yoshizaki and his team's research were published in Science.

SOURCE:

Nicola Jones, Salmon parents give birth to trout.