Tag Archives: medusa

Who Needs Mythical Beasts? Rocket Jellies, Snakelocks Anemones and a Dragonet

When my son was younger he thought he saw a kraken. I returned from releasing a crab after an event for the local Cub pack to find him and a friend staring out over the sea, shading their eyes to better spot tentacle tips or unusual splashes among the waves. They were quite sure it was out there.

I watched with them for a long time, until the tide was lapping at our boots, because you never know what might be in the sea. A giant squid would be unusual, but our oceans are full of things that are so weird we are only just beginning to understand them. We sometimes see seals, dolphins and fish feeding frenzies, so why not a kraken?

Since then, my son has grown up a lot and is less sure that there are krakens in Looe. We no longer spend much time hiding in the woods looking for dragons or watching the waves for sea serpents. Junior still loves mythology, Cornish and otherwise, but knows that the real world has as much strangeness as fiction.

We are two minutes into this week’s rock pool expedition when he calls to me urgently to look at a thing he’s found.

Junior at work!

“I think it’s a hydroid medusa,” he says, because there’s not much he doesn’t recognize these days. “Quick, it’s going to get away.”

I grab a pot and wade over to where he is pointing. Staring into the tangle of colourful seaweeds, at first I see nothing.

A flicker of movement has me scooping up the water and when I look in my pot there is a tiny creature zipping from side to side, throwing itself against the edges of the pot like a trapped Trogglehumper. Of course, this creature is not a Roald Dahl creation, but an actual, fabulous marine animal. My books call it a ‘root arm jelly’, although Junior and I know it by a different name.

Whoosh! A rocket jelly. (Cladonema radiatum – aka the root arm jelly).

“Rocket jelly!” we shriek in delight.

With great care, we transfer the jelly into the lid of the pot to see it better.

The underside of the hydroid medusa (Cladonema radiatum – the root arm jelly)

The main part of its body, measuring less than a centimetre, is a perfectly transparent dome, through which we can see its rocket shaped internal parts. Pointing downwards, a mouth fringed with ball-shaped structures is feeling about, moving left and right.

The jelly’s transparent body with dark eyespots around the edge. Root arm jelly (Cladonema radiatum).

At the base of the medusa’s dome there are several dark eyespots. Spreading out at around them, like the fire below a rocket, are the most incredible red tentacles. They are branched, curled and almost feathery. As we watch they expand and contract, feel and reach.

Every time I focus on the medusa, it fires itself off in a new direction. Zooming from one side of the petri dish to another in an instant.

I have never seen a medusa with such expanded tentacles before, but I am sure this is the same species of ‘rocket jelly’ we have seen before (Cladonema radiatum).

Those little tentacles pack a strong sting for their size; it is an efficient little predator. I always find it hard to comprehend is that this free-swimming, speedy jelly is the reproductive stage of a colonial hydroid: an organism which lives attached to rocks or seaweed and doesn’t move from the spot.

Obelia geniculata - a hydroid known as 'sea fir'.
Hydroids like this sea fir, Obelia geniculata, live attached to seaweeds.

While Junior takes photos of the rocket jelly, I notice a young fish glide over the sand, stopping near my feet. It has mottled markings in blue, orange and brown, which look colourful and yet provide the fish with an ideal camouflage among the sand, pebbles and shell fragments. Its eyes are mounted high on its head, giving it a wide field of vision. This is the wonderfully-named dragonet.

Dragonet lying still on the sand. Despite the lovely colours, it is perfectly camouflaged.

These captivating fish have a distinctive way of swimming in short bursts across the seafloor and they have an exceptionally long first dorsal fin. Male dragonets raise this sail-like fin as part of a mating dance, which I would love to see some day! It is perhaps this display, somehow reminiscent of a frill-neck lizard opening its collar, that gives these fish their fabulous name.

Dragonet saying hello to my camera!

The dragonet comes unusually close to my camera before scudding away over the sand, becoming invisible every time it stops.

I take some photos of another striking animal with a mythical name, which seems to abound in this pool: the snakelocks anemone. Just like the Medusa of Roman mythology, this anemone has long, green moving ‘hair’. Instead of being made of snakes, though, the anemone’s locks are its stinging tentacles. They are pretty but deadly, especially if you are a small animal, or even quite a big one. We’ve often seen crab legs hanging out the mouths of these large anemones.

Snakelocks anemones in the rock pool.

Some snakelocks anemones are neon green with purple tips, while others are a muted beige colour. Out of the water, they are a sorry squidgy mess of jelly but in the pools their tentacles move and flow, sometimes with the current, sometimes reaching and grabbing for prey they have sensed.

Snakelocks anemone – some are green and some are beige.

The chug of a boat makes us look up. Unusually for this area, there is a dive boat close to the rocks. Two-by-two, people in Scuba gear pop up on the surface and clamber aboard. I wonder what they have seen and whether they have noticed the tiny rocket jellies, lurking dragonets or even the medusa-haired snakelocks anemones.

Dive boat close in to shore.

Perhaps the divers have seen the kraken as they’ve explored the sea just beyond our reach. Even if they have, we don’t feel we have missed out by being confined to the land. The rock pools are full of truly magical beasts. You just have to look.

Snakelocks tentacles waving in the current.

Baffling jellies, a little shark and a possible giant – A day in the Cornish Rock Pools

Sometimes everything’s just meant to be. This is one of those times.

It’s a random get-together; my Twitter friend Nanny Pat from Bosinver Farm Cottages has suggested we meet with her family and friends to explore a special beach that her son loves. Sounds good to me!

The view towards Falmouth, Cornish Rock Pools
The view towards Falmouth

The sun is struggling through the clouds as we all descend from Mawnan towards the glittering shore. We are nine adults, six children, one dog, some huge buckets and a promisingly enormous picnic bag that Nanny Pat has packed for us.

We waste no time and strike out across the slippery rocks. These are serious rock poolers. I am, as other half puts it, “among my people”.

Just one more rock... exploring the Cornish rock pools
Just one more rock… exploring the Cornish rock pools

We set to and the finds flood in. There are fish eggs everywhere, some are just starting to develop like these clingfish eggs.

Cornish clingfish eggs are a distinctive yellow colour
Cornish clingfish eggs are a distinctive yellow colour

Others are nearly ready to swim away, eyes jammed against their transparent egg cases, tails squished around them.

Ever feel like you're being watched? Fish eggs in a rock pool.
Ever feel like you’re being watched? Fish eggs in a rock pool.

Best of all, I’m baffled by some of the creatures we find.

The medusa (jelly) stage of a hydroid or sea fir - possibly clytia hemisphaerica or similar
The medusa (jelly) stage of a hydroid or sea fir – possibly clytia hemisphaerica or similar

First there’s a transparent disk of jelly a centimetre across. I scoop it up in a tub and peer at it until I go cross-eyed. It shows no sign of life, but I’m sure it is an animal. All around its rim are mauve dots and a thin purple cross hangs across its centre.

The underside of the medusa
The underside of the medusa

I rule out all the UK jellyfish and it’s the wrong shape for a sea gooseberry. When I take a photo of it in the water, my camera shows some short tentacles, invisible to the naked eye.

Having since consulted the experts, it looks to be the medusa (jelly) stage in the lifecycle of some sort of hydroid or sea fir.

Swimming free - the side view with tentacles showing.
Swimming free – the side view with tentacles showing.

I’m distracted from my observations by some excited shouts and squeals. “Quick, we’ve found a shark!” one of the adults calls.

The children are gathering around the edge of a pool and there in some shallow seaweed, a dogfish (small spotted catshark – scyliorhinus canicula) lies stranded.

Scyliorhinus canicula - small spotted catshark or dogfish stranded in a Cornish rock pool
Scyliorhinus canicula – small spotted catshark, also known as dogfish – stranded in a Cornish rock pool

The animal is calm despite being out of the water and surrounded by eager kids. We take a minute to take photos. Some of the children tentatively touch its sandpaper-rough skin and Cornish Rock Pools junior sluices it with water in an effort to keep it happy.

Close up you can see the rough skin (that used to get used as sandpaper) and the cat-like eyes
Close up you can see the rough skin (dogfish skin used to be used as sandpaper) and the cat-like eyes

The dads rush in for the privilege of relocating our shark to a deeper pool, where it lurks as we carry on our rockpooling.

The 'rehomed' catshark waiting for the tide to come in. It was so well camouflaged it was hard to spot among the seaweed.
The ‘rehomed’ catshark waiting for the tide to come in. It’s so well camouflaged it’s tricky to spot among the seaweed.

One of the finds, a little fish catches my eye. When I first see its red body and dark head, I think it could be a black-faced blenny. The shape doesn’t seem right though. After much staring, I conclude it’s probably a scorpion fish. In my photos the spines on its face can be seen more clearly, confirming that it’s the smallest specimen of this species I’ve ever seen.

A juvenile scorpion fish - the smallest I've ever seen
A juvenile scorpion fish – the smallest I’ve ever seen.

The picnic is perfect in every way. Some of the children huddle together with their sandwiches on top of a tall rock. The smaller kids play in the sand and shower some into the olives, but no one cares.

The tide has moved in but there’s still time for some last-ditch rock pooling to the east of the beach. One of the boys is desperate to find and eel and his determination pays off. He locates a good-sized common eel under a rock, but it slithers into a crevice, evading capture.

Love is in the air! Berthella plumula sea slugs under a rock.
Love is in the air! Berthella plumula sea slugs under a rock.

There is no shortage of crabs here and we find pairs of lemon-yellow berthella plumula sea slugs clinging to the underside of the rocks. I’m told there are giant gobies around and it’s not long before one of the dads sends up a triumphant cry. “It’s a giant.”

It's a whopper, but is it a giant? Goby found in a mid-shore pool
It’s a whopper, but is it a giant? Goby found in a mid-shore pool

We all look closely. I’ve seen some big rock gobies and I know they can be hard to tell apart from the rarer giant goby. This one looks like it could be the real thing. It’s large, at least 17cm, and has the fat-lipped face and salt and pepper colouring of a giant goby.

The goby's face showing the super-thick lips.
The goby’s face showing the super-thick lips.

I take photos of the sucker fin on its belly and hope we’ll be able to get a definitive answer from the experts. The giant goby has a detatched lobe at the front of its sucker fin which the rock goby doesn’t have…apparently.

The pelvic sucker fin of the goby
The pelvic sucker fin of the goby

As we release the goby into the pool where we found it, the children spot their granddad walking onto the beach. He’s arrived just as the tide overtakes the last pools and he invites the kids to join him for a spot of skimming.

It’s the first time I’ve been to this beach. I think I’ll be back.  Some things are indeed meant to be.

Brittle star
Brittle star


A good sized three-bearded rockling
A good sized three-bearded rockling