hybrid embryos of critically endangered rhinoceroses manufactured in the laboratory

Embryos are ready for a first attempt at IVF.

It is the most endangered species on earth: the northern white rhino. The last male died in March of this year and for the moment only two females are alive. It does not look good for this beautiful species.

Embryos
But shortly after the death of the last male, scientists have already announced that they are not giving up yet. With the help of stored sperm from male white rhinos already dead, it should be possible to fertilize the remaining female white rhinoceros ova. And perhaps the resulting embryos could then – perhaps in a surrogate mother – become healthy northern white rhinos.

Hybrid
This sounds wonderful, but there is a problem: there are few available oocytes. And that's why researchers have now taken a different approach. They collected oocytes from the southern white rhinoceros, closely related to the northern white rhinoceros, and fertilized them with sperm from dead white rhinos from the north. The result is a hybrid embryo that contains genetic material from the northern and southern white rhinos.

Primeur
This is a first. IVF has already been used more often in large mammals – such as horses – but never have researchers succeeded in turning a rhinoceros embryo out of the body into a blastocyst: a hollow pellet formed when dividing the body. 39, fertilized egg. The blastocyst is in principle ready to be implanted. But the researchers have frozen them for the moment. Perhaps they will be placed in the womb of a surrogate – a southern white rhinoceros.

Intersections
With this approach, the northern white rhinoceros is of course not saved. Because even if she succeeds in growing the embryos of a surrogate mother into healthy young rhinos, they are not white rhinos, but crossbreeds. However, it is promising, because with this approach, it is possible to preserve some of the genetic material of the northern white rhinoceros.

In addition, the generation of young rhinos from these hybrid embryos is not the end point of the researchers. In this way, they continue to try to collect eggs from the two still-living Northern White Rhinos. And maybe with that we can make embryos from which a true northern white rhinoceros can grow.