While scientists have known about multiple animals that can turn sunlight into energy, they haven't been sure that any vertebrate could do so - until now.

As far back as 1888, a biologist found that the eggs of a spotted salamander contained a kind of green algae, but now firm evidence now exists that the animal is powered by the sun, reported the New Scientist and according to research published in the Journal of Experimental Biology.

The process takes place inside the eggs.

Scientists in 2011 found that the algae was not only present inside the eggs, but inside the embryonic cells themselves. The theory, which proved correct, was that the algae, through photosynthesis, used sunlight to trigger a chemical reaction combining water and carbon dioxide to produce glucose, or sugar, that the embryo used for fuel.

The algae is not essential, but Erin Graham, a professor at Philadelphia's Temple University who led the study, said in the paper, "Their survival rate is much lower and their growth is slowed" without it.

Graham also said there could be more such animals, though they would likely be other amphibians or fish.