The box jellyfish isn’t just a simple blob of goo. It’s an active predator that hunts with 24 eyes. These are clustered into four groups of six. In each cluster, four eyes are simple pits or slits that sense the presence of light. The other two actually see images and they’re remarkably similar to our eyes. They have their own lenses, retinas and corneas, and they’re even made using very similar genes. Even though we’re separated by millions of years of evolution, box jellyfish and back-boned animals have evolved eyes by independently recruiting the same building blocks.
The eye clusters are weighed down by heavy crystals so they're always upright, even if the jellyfish is swimming upside-down. This gives the animal a perpetual view of the sky, which allows it to stay close to the mangrove forests where its prey lives.
(Photos by Anders Garm)
Read more: Jellyfish and human eyes assembled using similar genetic building blocks