Flowers of the ocean
Sea anemones and the mystery of their coloration
Close up of a strawberry anemone, with its characteristic spotty column. The blue beads are used in fighting other anemones.
Anemones are one of the most beautiful and diverse ocean creatures. In the UK there are over 40 species, often differing greatly in colour among, and even within the same species. But bizarrely, there's little consensus as to why they look the way the do and what their coloration is for.
A green and purple snakelocks anemone on the rocky shore.
Around Cornwall, a handful of species are especially common, most of all the snakelocks anemone. They come in two main colour types: green with purple tips, or grey-brown. The morphs may exist thanks to different amounts of symbiotic algae that live within them, and also how much light they require to thrive. This could mean that different colour types should be more common in either shallow or deeper water. But this is not what's normally seen - both grey and green forms often occur together (except strangely on seagrass, where brown types dominate).
Close up of a dahlia anemone with yellow tentacles.
Some anemone species are even more varied. Dahlia anemones exist in many hues and patterns, from those with tentacles of deep purple, to red, yellow, or transparent with dark banding. Often being very conspicuous, the anemones may use their colour in defence - to warn potential predators that they have a powerful sting, or instead to lure inquisitive prey towards them. Other stunning species include gem and red speckled anemones, which have intricate markings and a variety of pink, green, and other colours.
The blue tentacles of a daisy anemone.
By contrast, daisy anemones, alongside other species, are largely inconspicuous. Up close, they look quite colourful, some with stunning blue banding, but on the whole they blend into the gravel seabed and rocky crevices they call home. Like the dahlia, their coloration may help them to avoid attack by predators or to capture prey, but by hiding instead of sticking out.
A colourful yet tiny gem anemone.
Many anemones respond to the intensity and spectra of light; some species retract their tentacles when under intense ultraviolet light, perhaps to avoid damage to their body tissues. Yet they can't see actual images or objects, so they don't have a sense of vision that they could use to communicate with one another. Any use of their coloration must, therefore, be intended for other animals, but exactly why anemones look the way they do, and why they vary so much, is yet to be determined. Either way, they make a stunning subject for underwater photographers.
A striking purple form of dahlia anemone.