The Ludwig Maximilians University researchers injected photosynthetic algae into the tadpoles, creating a symbiotic relationship between amphibian and microbe that keeps the amphibians alive without any environmental oxygen, The Scientist reports.

It’s an odd experiment that could have important medical value — keeping someone alive when a stroke cuts off their brain’s oxygen supply, for example — but it’s also a fascinating step forward in biological experimentation in its own right.

In order to test their new hybrid, the researchers starved the tadpoles of oxygen until their brains shut down completely.