I have never seen a species quite so\u00a0flamboyant in appearance. A couple of centimetres in length, it\u00a0was curled beneath the submerged rock like a piece of gaudy costume jewellery.<\/p>\n
When the cry went up that one had been found, I had to prevent myself from breaking into a run as I navigated the slippery seaweed-covered boulders to catch my first glimpse of this rarity.<\/p>\n
A sea slug. And yet a species that does everything possible to dispel any idea that slugs are drab and dull. The extravagant rainbow sea slug comes with a \u201cta-da!\u201d. Typically found along the coasts of Spain and Portugal, this multicoloured member of the Aeolid nudibranchs family has spread north with warming seas<\/a>, and was first recorded in the UK off the Isles of Scilly in 2022. It has since secured a toehold in southern bays of Cornwall and Devon.<\/p>\n I had joined a \u201cbioblitz\u201d, run by the Rock Pool Project<\/a>, on a low spring tide in Falmouth. The community organisation\u2019s monthly challenge engages members of the public in a citizen-science survey of seashore life. The rainbow sea slug was a star find, drawing an admiring huddle of enthusiastic rockpoolers. Breathtaking and bizarre, its outlandish confectionary of candy colours looks almost artificial. The vivid pink body is decorated with a mane of blue finger-like projections known as cerata, which are topped with yellow and orange. A pop-art palette of colours designed to warn predators that it is unpalatable.<\/p>\n \u2018This one was found on the underside of a rock beside white circles of recently laid eggs.\u2019 Photograph: Charlie Elder<\/p>\n This one was found on the underside of a rock beside white circles of recently laid eggs \u2013 the next generation of these sensational little sea creatures.<\/p>\n The project volunteer and marine\u00a0biologist Ellie Maynard told me that she encountered her first rainbow sea slug last Christmas. \u201cSince then I have seen upwards of 20 here,\u201d she said. \u201cIt has been really rapid how they have grown in number.\u201d<\/p>\n It was far from the morning\u2019s only rarity. Others included the wonderfully named hair curler slug<\/a>, which first reached the UK last September and has wavy brown cerata that give it a\u00a0permed\u00a0appearance.<\/p>\n The rainbow sea slug we were watching eventually trundled off, like an overdressed performer\u00a0late\u00a0for a carnival. Show time was over.<\/p>\n