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Jellyfish species in the UK found on Cornwall’s coast

When going on our recovery missions we often find more than just plastic – as the waters around Cornwall have started to heat up this month we’ve been enjoying a smack of jelly sightings – and been admiring their amazing diversity of forms and colours.

stalked jellyfish species

Stalked jellyfish - Hard to spot

The rare Stalked Jellyfish are bizarre oddities of the biological world – only 2cm long these tiny jellies have evolved to a settled life, attaching themselves with a little anchor to seaweed and rocks. They filter microbial prey out of the currents with their flower-like projections and unlike most jellyfish they prefer the cold waters of the U.K. There are two types of these rare jellyfish found in Looe: Calvadosia cruxmelitensis and Calvadosia campanulata. Sadly its unlikely you will have ever see them as they blend incredibly well with their surroundings, unnoticed except by those who seek them out.

moon jellyfish species

Moon Jellyfish - Harmless

Moon Jellyfish are the best jellyfish to unexpectedly find with your foot – they don’t sting. Found all around the world the Moon jellyfish is a common sight washed up on the beaches and coves between Looe and Polperro. They grown to the size of a dinner plate and are transparent expect for four pinkish-purple circles – which are their gonads! Other than this they only have a stomach – no brain, heart or eyes to speak off. To eat they use their tiny tentacles to catch microbial plankton.

barrel jellyfish species

The Barrel Jellyfish - A Gentle Giant

Barrel Jellyfish are humungous barrel-shaped and barrel-sized jellyfish with a huge thick dome and eight ornate frilly flowing tentacles. Despite their size they aren’t dangerous – they only give a mild sting. They swarm in late spring and summer in the bay, attracted by great plankton blooms which they feed on. In turn, later in the year Leatherback turtles are spotted off Cornwall in hot pursuit – the Barrel Jellyfish are their favourite food.

blue jellyfish species

Blue Jellyfish - Food For Turtles

This Blue jellyfish’s species isn’t the only thing that can be identified by colour of their bell – you can also tell their age! Blue’s are paler in appearance when young, but mature purple-blue (some are more yellow) colours in their main body.

Blue Jellyfish species grows to different sizes in different places – growing smaller in cold northern waters 15cm and bigger in warmer waters – upto double their colder cousins at 30cm max size!

These jellyfish drift closer to the shore to catch the large abundance of plankton with their many stinging tentacles – then scoop up their stuned prey with four mouth/arms that are larger with many wrinkles and ripples – evolved with a large area to absorb nutrients from the plankton. Their stinging arms have a double function – deterring from a slow moving brainless jelly all but the most specialist predators such as turtles.

compass jellyfish species

The Compass Jellyfish - A Brainless Angler

Compass Jellyfish are another common sight in Cornwall – a translucent pinky-yellow dome about the size of a saucer with long flowing tentacles and a brown pattern of lines that resembles a compass: hence the name.

If you see one of these critters, give it a wide berth, their fine almost invisible tentacles give a vile sting unlike most of the other common UK’s jellies on this list that have no/mild stings. To add to the fun they often detach their tentacle which keeps stinging when no even attached -if you do get stung scraping the sting clean or removing the tentacles with tweezers, followed by washing with warm water is the best cure.

Weirdly for a jellyfish that eats small fish – young fish are often seen swimming around the jellyfishes tentacles. Whilst its clear the fish get protection from the odd arrangement its unclear why the jellyfish don’t sting and eat the fish. One idea is that the jellyfish lets some fish into its protection, so they act as bait to catch others – very clever for a creature without a brain!

comb jellyfish species

Comb Jellyfish - Little Living Lightshows

Comb Jellyfish are the tiny laser-shows of the sea.

Tiny simple pocket-shaped creatures they stand out for their cilia – which when the suns rays hit become little shimmering rainbow coloured fibres. Comb Jellies are technically not Jellyfish – despite their well thought out name –  and are part of their own Ctenophore family of animals.

The most distinctive feature of comb jellies we see here in Cornwall, is not surprisingly the “combs” that run down the side of its body. There are usually eight combs and the ‘teeth’ of these combs are called cilia which are used for swimming. Comb jellies are the largest organisms to use this method of movement – its what microorganisms a million times smaller do normally. The rainbow effect that is seen during the day travelling up and down the side of a comb jelly is caused when the cilia move slightly out of sync with the next. This causes a scattering of light making them look like out-of-this world rainbow animals.

The comb jelly type above- called Nuda – have no tentacles at all and look like a swimming mouth (like a natural pac-man) that can “bite off” pieces of prey. And whilst nuda and all other comb jellies today are entirely soft-bodied today their ancestors a staggering ½ billion years ago had hard skeletons like us and can be found in stunning yet incredibly rare fossils.

Comb jellies whilst beautiful – can be a nightmare when us humans start moving them around in the bilges of ships – One comb jelly species decimated the fish of the Black Sea when it was introduced by humans accidentally, eating both fish larvae and the food of adult fish in the entire enormous sea. Ironically it was the introduction of a another species of invasive comb jelly that brought populations under control and stopped the onslaught of the boneless killers.

Leatherback Turtles - The Jelly Devourers

Leatherback Turtles are becoming ever more frequent summer visitors – the only species of turtle large and adapted to survive our cold waters. These eternal wanderers live century long lives, growing into gentle giants two meters in length and up to 900kg. Leatherback turtles travel alone, feeding on jellyfish (and siphonophores like the man of war – more on them later) and only come together in warm tropical waters to breed. Leatherbacks are particularly vulnerable to plastic. This is because they have a spiny oesophagus – a tooth-filled throat – that traps their wobbly prey and plastic inside them. Leatherbacks are the UK’s only marine reptile.

The Impersonators

by the wind sailors

By The Wind Sailors - Living at the whim of the Winds

Tiny dark blue discs – often mistaken for the much more common plastic pollution that resembles them – mysteriously appear as Winter approaches. However these weird discs are alive – brought by the violent storms of the Atlantic to our shores. 

They are the aptly named – by-the-wind-sailors who use their thin, semi-circular fin as a sail, trawling for invisibly small prey behind with tiny short tentacles in the water. Living at the mercy of the winds – they end up in massive groups washed up together onto the land during storms.

This incredibly strange and beautiful species is known as a colonial hydroid. They are similar to the Portuguese Man O’War (below) as they are made up of a colony of tiny individual animals – and in fact  are not true jellyfish.

man of war jellyfish species

Man Of War - Four Animals Working as One

The Man of War is not a jellyfish as it appears – nor even is it even one animal. These weird eletric-bluey-pink, pasty-shaped, real-life balloon animals wash up in the autumns along Cornwalls shores.

They are actually a creature known as a siphonophore – a type of carnivorous colony made up of several individual animals called zooids. These zooids each work together in their own special role. Only by working together can they co-exist. Imagine your legs, arms, guts and head all having a separate brain and cooperating?

Read about The Sharks of Cornwall or Man of War in Cornwall next.

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