Unlike clams, the heart cockle doesn't need to open wide to bask in the sun. It has a clever trick up its shell: tiny, transparent windows.

Heart cockles have windows in their shells made from natural optical fibers, allowing light through to the algae inside them.

Detection of light is a basic need for everything from devices to plants and animals. In the case of animals, light detection systems are very highly specialized, and often operate very near to ...