For a scuba diver, one of the best underwater sights is a rock face covered in brilliantly coloured jewel anemones (Corynactis viridis). They exist in many colours, and often vivid contrasting colours are found side by side. There are also subdued, semi-transparent variants.

Most species of wild animals have evolved to just one or a narrow range of colours, while flowers can have a range of vivid colours, presumably to attract a variety of insects.

As far as I know, the anemones aren't trying to attract their prey - it just arrives on the current. So why are they so vivid and so varied?

George Gall, Truro, Cornwall, UK

(Image: Kunstformen der Natur by Ernst Haeckel / Wikimedia Commons)