Salmon Made to Bear Trout

Cue the world’s most peculiar baby announcement: Masu salmon have produced rainbow trout offspring, with an assist from scientists that could lead to the preservation of rare fish species. Trout sperm stem cells had already been injected into salmon embryos to produce salmon with trout sperm; now the same early sperm cells have been used to produce female salmon with trout eggs, Nature reports.

Eggs can be extremely difficult to preserve; hence the importance of being able to produce viable trout eggs from sperm stem cells. Scientists also struck gold by using otherwise sterile salmon, ensuring a high success rate in the engineered breeding. The research demonstrates a remarkably high genetic flexibility among the fish—one that bodes well for their endangered relatives. (More salmon stories.)