I don’t scuba dive any more, but every now and then I am in the right place at the right time to see a nudibranch in a rock pool. These little creatures are molluscs, but ones that lose their shells early on in life. They are spectacularly coloured, thought to advertise what zoologists call ‘distastefulness’ – ‘I taste yucky so don’t waste your time attacking me’. A friend, Peter, took this photo of a chromodoris at Woody Head last year.
‘Nudibranch’ means ‘naked gill’, and you can see the pink gills at the rear (right) of the chromodoris above. The two pink things at the front (left) are called rhinopores, and scent or taste the environment.
Last weekend I found this one at the water’s edge, but had to move it to photograph it or risk both of us being washed away. It’s about 2 cm long. Neville Coleman, in his Nudibranchs Encyclopedia, calls it the scribbled doriopsilla (Doriopsilla miniata).
Aeolids like Spirulla neopolitana below are also nudibranchs, but don’t have an obvious ‘naked gill’ like the ones above. The frondy bits are called ‘cerata’, and, according to Wells and Bryce’s Sea Slugs of Western Australia, are ‘digestive gland extensions with thin walls allowing the ready exchange of gases’ – in other words, they have the same function as gills.
There are supposed to be about 3000 species of nudibranchs – and that’s just the scientifically known ones – so you could spend a lifetime or more getting to know these fabulous jewels.