It measures one centimeter. It fits on your fingertip. And it does something no other animal in the world can do: photosynthesis.
It is called Costasiella kuroshimae, although everyone knows it as the leaf sheep, and it has lived hidden in the tropical waters of Japan, the Philippines, and Indonesia since long before science first described it in 1993, off the Japanese island of Kuroshima. Its trick is as simple as it is extraordinary: when it eats algae, it does not destroy their chloroplasts; it stores them intact inside its own body and continues using them to produce energy, as if it were a green leaf with eyes.
That biological oddity was enough for hundreds of thousands of people to vote for it as Invertebrate of the Year 2026 in The Guardian’s annual contest, presented by activist Chris Packham. In a closer race than ever, it beat the botfly, the largest bumblebee on the planet, which came second. A reminder that 97% of the world’s animals do not have a backbone, and yet some of them perform magic.
