Wildlife Wonders: Bioluminescent Jellyfish in Cornwall

Cornwall is known for its natural beauty, think unspoilt beaches, enchanting woodlands and wild moorlands. But what about the beauty that lives in our waters? Jellyfish are mysterious creatures, the fascinating gelatinous specimens have been around since prehistoric times, with weird-looking bodies and dangling tentacles. Despite their name, they are also not actually fish, they are plankton, some of which reach mythological proportions. While they inhabit the water, they’re not great swimmers, and largely float along in the water (they are 98% water themselves).

There are six species that have had multiple sightings in Cornwall’s waters, most commonly appearing in the spring and lasting through to autumn. On the whole, they are unharmful to humans with only a few stinging, however sting strengths do differ, please see NHS advice on stings here. Remarkably, jellyfish have no brains, no hearts and no blood – they can also regenerate themselves if they get damaged and some can even clone themselves.

While we may be used to seeing jellyfish along the Cornish coast, there’s one species in particular that has been spotted along the coastline, creating quite a visual masterpiece, where the sea sparkles with an ethereal greeny blue glow. The Aequorea victoria, more commonly known as the Crystal Jellyfish. A visual spectacle, they are known to illuminate and can eat jellyfish bigger than themselves. With a transparent body, and beautiful fine lines coming out from the centre, when it’s disturbed, this bioluminescent jellyfish can glow in the dark, because of its green fluorescent protein and having more than 100 tiny, bioluminescent organs – in other words, organs that emit light. It’s a special superpower, which is handy both for attracting prey and distracting predators, and provides a beautiful display.

The crystal jellyfish is rarely seen in the UK, other than off the coast of Cornwall, with experts putting the more recent sightings down to an “indicator of warmer seas”. It probably comes down to climate change. Hotter weather and warmer seas are encouraging creatures to visit us who didn’t before. Over the past decade the crystal jellyfish seen at Cadgwith, on the Lizard Peninsula, Falmouth Bay and Looe Island.

Also lighting up the water in Cornwall, is Salps. A relative of sea squirts, Salps are tunicates and live in the open oceans. While they are rare visitors to Cornish waters when the conditions are right, because they reproduce and grow rapidly, it can create huge booms with thousands being spotted at one time. It’s the sea creature’s filter feeding chains which create ‘fairy-light’ like structures in the water. Recent sightings include near Porthcurno beach and Fowey.

Jellyfish are wonderful to see in the water from a boat trip, or in a sea life centre, but something to be aware of if you are swimming in Cornish waters. Obviously, if you see one, admire from a distance but don’t touch it with your bare hands, else you might well get more than you bargain for. To find out if there are jellyfish sightings in your local area, visit the Marine Conservation Society.