Days like this don’t seem ideal for rock pooling; the tide is nowhere near low enough to expose my favourite pools and the weather is iffy. Despite this, I am convinced that there is plenty to see on the mid-shore. Cameras and rock pooling super-crew (Other Half and Junior) at the ready, we set out to uncover marine treasures.
One advantage of neap tides, when the sea doesn’t go out very far, is that it won’t rush back in either. We can take our time. Junior soon locates lots of gem anemones with their tentacles wide open.
Gem anemone
Under a stone further down the shore, I spot a beautifully camouflaged anemone. It’s too small to see properly, so I have to wait until I get home to confirm that it’s a Sagartia troglodytes anemone.
Sagartia trogladytes anemone
The B shape at the base of the tentacles is a useful identifying feature, although I’ve always thought they look more like Scooby Doo ghost eyes than letters.
Other Half calls me over to look at a blob. He’s becoming quite an expert blob finder.
We look together at the tiny brown jelly-spot on the seaweed. At first, we think it is an anemone because it seems to have a circle of retracted tentacles. As soon as I dunk it in the water though, I can see the pale lumps of primary tentacles around the edge. It must be a stalked jellyfish.
Is it just me or does this stalked jelly not look pleased to see me? Haliclystus octoradiatus.
Gradually, the stalked jelly unfurls each arm until it looks much less blob-like.
Haliclystus octoradiatus -starting to look more like a stalked jellyfish than a blob.
The rain seems to be holding off now, and I make myself comfortable by a calm pool to watch the little world go by. My camera has barely entered the water before a bold prawn trots out of the seaweed, its legs working at top speed in its eagerness to check out what I’m up to.
Common prawn coming to take a look at my camera.
Common prawn
A head pops up between the fronds of saw wrack at the back of the pool. The young Montagu’s blenny swivels an eye back and forth beneath its jaunty headgear. I feel a larger blenny move through the seaweed near my hand and lift my camera out of the water before I get a nip from the territorial shanny.
Peek-a-boo! Montagu’s blenny taking a look above the serrated wrack.
Montagu’s blenny.
A dinky starfish in the coral weed catches my eye. I see several species of starfish on this beach, but this is a mid-shore specialist: Asterina phylactica. The colours of the tiny pincers on its back (the pedicellariae) form an orange star shape. Under the camera, I can see its tube feet reaching out and exploring its surroundings as it glides along.
Asterina phylactica – cushion starfish
Other Half brings passes me a tiny shell he has found. He thinks it might be a wentletrap, a shell we sometimes find. I have never seen one so small and assume it is probably a different species. I take a look with the camera and realise he was right. The bold sculpture of ribs over the rounded whorls of the long spire are striking, even in this tiny juvenile. Best of all, the shell is occupied.
Juvenile wentletrap
I watch the snail emerge and set off across the pool.
This makes me think of a unicorn and a rainbow – juvenile wentletrap.
Sea squirts are something of an enigma to me. They are hugely varied in their colours, shapes and sizes. Aplidium turbinatum, in particular, seems to me to look different every time I find it. When I first see this one, I am convinced that the white, spiky-looking set of openings under the coral weed is a bryozoan.
I know this looks familiar, but takes me a long time to work out that it is Aplidium turbinatum, a sea squirt.
Yet, after a while watching it, I realise it is opening and closing like a squirt, puffing water in and out. It bears little resemblance to the orange gelatinous Aplidium turbinatum I usually see further down this beach, but the jutting triangular crowns around the edge of each opening are the same.
Aplidium turbinatum sea squirts
Fortunately, I can turn to the incredible Aphotomarine website for confirmation and, sure enough, it has some photos of very similar specimens (thanks David!).
While the tide seeps back into the pools, we chat with a fellow rock pooler whose photos I have often seen online, and who I eventually realise I have met before in real life through another conservation group.
Chthamalus sp barnacles starting to open as the tide comes in.
By the time we leave, the sun is low in the sky. I am more than satisfied with all the wonderful creatures I have found on the neap tide, and it is high time I had some birthday cake.
Strawberry anemone
Whatever the tide, always stay safe in the rock pools. Follow my rockpooling tips to look after yourself and the wildlife on the shore.
This website is a labour of much love and the content is available for free to everyone. My wonderful readers often ask if there is a way to support my work. You can now ‘buy me a coffee’ through my Ko-fi.uk page. (Just click donate and you can set the amount to pay by PayPal). Thank you!
Junior’s enthusiasm takes me aback. He has a healthy aversion to getting close to jellyfish. We have already changed course many times on today’s high tide swim to avoid the trailing tentacles of compass jellyfish.
The distinctive markings of the compass jellyfish.
These common summer visitors have striking brown V-shaped markings around their edges, like the points of a compass. Although their sting is rarely serious, somewhere in the region of a stinging nettle in strength, it isn’t much fun if you swim face-first into one as I have done on a few occasions.
Crystal jelly. This is a hydroid medusa rather than a ‘true’ jellyfish. It has short tentacles around the edges rather than long trailing tentacles.
Some other species we have seen this week, like the moon jellyfish and crystal jellyfish, are harmless but today only the compass jellies are out.
Moon jellyfish only have a very weak sting so are usually harmless to people. Never touch a jelly if you’re not sure of the species and wash your hands well before touching your eyes.
Incredible numbers of sand eels fill the water in every direction, flashing silver as they turn, before melding into the green sea. Junior notices a small spotted catshark (Scyliorhinus canicula) – also known as dogfish – swimming through a rocky gully beneath us. Alongside submerged rocks, several species of wrasse flit among the kelp.
This sand eel is speeding along – photo by Junior
I unclip the camera from the safety float and pass it to Junior who is pointing excitedly at something I can’t see.
I dip under the water and look at where he’s pointing. Still nothing. I bob up for air and try again.
This time I see something much smaller than I was expecting, or half see it – it’s mostly transparent with just the faintest pink hue.
Comb jelly – photo by Junior
“Is it a comb jelly?” Junior asks. This is the first one he’s seen and much excitement ensues as he tries to photograph a barely visible tiny swimming thing while holding his breath and floating in water 5 metres deep.
Comb jelly by Junior. The transparency of the animal and its movement in the water make it hard to focus, but you can see the shining light of the combs.
Mostly we just enjoy the incredible coloured light show this Beroe cucumis comb jelly is putting on for us. The iridescent disco-light effect is created by lines of beating hair-like cilia (the combs) that run the length of the comb jelly’s body.
This species looks like a simple hollow tube or sack, but it is an efficient predator, known to feed on other comb jellies.
The different colours of the lights around the edges of the comb jelly are incredible to watch. Photo by Junior.
How Junior spotted this little speck in the ocean, I have no idea. We look around for more but find none.
Comb jelly by Junior.
Eventually we have to head back to shore, drifting over all of our familiar rock pools on the way. Hermit crabs and netted dog whelks are out in force and as we near the beach, we see shannies basking on sunny rocks in the shallows.
There are lots of these ‘south clawed’ hermit crabs (Diogenes pugilator) on the sand. Their left claw is much longer and larger than their right.
This might not be rock pooling in the usual sense, swimming on a high tide gives us a whole new perspective on life here. You don’t need to be a billionaire to become weightless and take a soundless flight over the rock pools. There is no better way to see how this environment looks for most of each day, when the wider ocean and the shore cross over and become one.
Swimming in the sea in Cornwall is a wonderful experience but is very different from swimming in a pool and can be dangerous. Always consider the conditions and stay well within your limits. Check the weather, tides and currents, enter the water slowly and adjust to the temperature. Choose a lifeguarded beach if possible and a place where you know how to safely enter and exit the water. Swim alongside the shore. A tow float makes you more visible and beach shoes can protect you from weever fish and sharp rocks. Don’t swim alone and let someone know where you are. In any emergency at sea or on the shore, call the Coastguard on 999.
This website is a labour of much love and the content is available for free to everyone. My wonderful readers often ask if there is a way to support my work. You can now ‘buy me a coffee’ through my Ko-fi.uk page. (Just click donate and you can set the amount to pay by PayPal). Thank you!
Irys and her mum are hoping to see a sea slug. As regular readers of this blog will know, I am more than a little slug obsessed, so we quickly hatch a plan to visit “Slug Alley”.
The day is grey and mizzly, as is typical in Cornwall any time of year. These damp conditions are ideal for sea creatures that would hide away on sunnier days to avoid drying out. The tide is nothing special, but there is still a fair chance of finding slugs if it drops enough to allow us to access the deep rocky overhang.
This flat periwinkle is happily searching for seaweeds among the damp sponges and sea squirts.
Tiny blobs of jelly aren’t easy to see, especially when the whole of the rock is coated in an assortment of blobs already. As well as some blobby seaweed, there is a rich turf of sponges, sea squirts and bryozoans, all competing for space in this damp, shaded area.
Star ascidian colonial sea squirts at Millendreath, Cornwall.
Among the hydroids I find a few super-small blobs that might be Doto sea slugs, but out of the water it is impossible to tell. Junior finds a “huge” stalked jellyfish a few centimetres long, which can only be a Calvadosia campanulata.
Calvadosia capanulata stalked jellyfish.
This jelly is common in the summer and can be a few centimetres long. The tiny turquoise spots on the outside of the bell are unique to this species.
Less obvious, but more numerous Haliclystus octoradiatus stalked jellies are everywhere at the moment.
Haliclystus octoradiatus stalked jellyfish.
I even find one under a stone. These stalked jellyfish normally only live on seaweed, so this one has probably been dislodged by something and will try to loop its way back to the seaweed when the tide comes in.
Stalked jellyfish under a stone looking rather sorry for itself!
Irys finds a blob and shows me. It is small, brown and jelly-like and I am pretty sure it is a slug. I try not to get excited until we are sure. Carefully, we remove it from the sponge and pop it in a pot of seawater. In true magic slug style, the little creature sticks itself to the bottom of the tub and begins to open up and move. This is not either of the species I first thought it might be.
Irys’s fabulous find – Aegires punctilucens, a nudibranch sea slug.
We transfer the slug to a shallow petri dish to get a better look. As soon as it is under the camera, it is obvious that this slug is indeed something different. It’s a species I have only seen before in my (many) books and it’s an absolute gem. It even looks like it is hewn out of rock with its bumpy, knobbly back, but between the bumps, the body is smooth, dark brown and decorated with spots of iridescent blue.
Aegires punctilucens sea slug at Millendreath
This is a fabulous find and I am in awe that Irys spotted it having never seen a sea slug before. I have to check the name in a book when we get home – Aegires punctilucens. Punctilucens means points of light shining through or dawning… a perfect description.
Aegires punctilucens sea slug exploring the pool at Millendreath.
We take a lot of photos of the slug in a petri dish and in a shallow pool before returning it to the rock where we found it, where it will feed on the sponges. Ideally we would take photos of it in situ, but out of the water it really is featureless brown goo!
The tide has dropped a little more, so we explore the pools further down the beach while we can.
Among a forest (or salad garden?) of sea lettuce, I spot this beautiful Polycera sp. slug. It is fairly large for this species and has striking yellow lines.
Polycera sp. nudibranch sea slug.
It is likely Polycera quadralineata, the four-lined sea slug, but it can be difficult to distinguish from Polycera norvegica. This lovely slug likes to eat bryozoans – colonial animals that form mossy sheets on the seaweed and rock – so it can become quite numerous this time of year.
Polycera sp. sea slug at Millendreath
I hadn’t been sure of finding much today on such a small tide, but slug alley has done us proud. We are all delighted with our finds and we are already planning another expedition together next time Irys and her mum visit.
Another creature in an unusual place – Aplidium turbinatum sea squirt on sea lettuce.
If you are visiting the beach this summer, be sure to rock pool responsibly and safely. Check the tides and leave everything as you found it. Read my top tips for successful rock pooling.
This website is a labour of much love and the content is available for free to everyone. My wonderful readers often ask if there is a way to support my work. You can now ‘buy me a coffee’ through my Ko-fi.uk page. (Just click donate and you can set the amount to pay by PayPal). Thank you!
It’s not often that you have the beach to yourself in Cornwall in July, but we want to show our friends the best Kernow has to offer. With this in mind, we meet Irys and her mum late in the evening to walk to our local shore and crunch across the sand to the rocks in the grey twilight.
Arriving at the empty beach before it is completely dark. (Photo by Other Half).
It doesn’t seem dark yet, but the birds are quiet, there are no other people about and it’s becoming hard to see where we’re putting our feet.
At night, it is especially important to put safety first so that you don’t find yourself in difficulty and have to get the Coastguard out of bed. We stick to a planned route on a beach we know well so that we will not be clambering over unfamiliar or slippery rocks. As always, an outgoing tide is safest and we arrive a full two hours before low tide so that we will leave before it turns. Sturdy boots and good torches are essential equipment, as are working phones and warm clothes. Our best-loved pieces of nighttime kit are our ultra-violet torches. Irys is trying hers out for the first time.
Testing the UV torch on some anemones. (Photo by Other Half)
The lack of predatory birds and drying sun makes life easier for rock pool inhabitants, so most of them are nocturnal. Creatures that we have to search for in daylight, such as prawns, crabs and fish, are all out and about looking for food.
Junior takes Irys straight to his favourite spot for seeing gem anemones. Under the UV torch they glow brightly, as does this snakelocks anemone. This fluorescence is caused by proteins that may help the anemone to survive in bright sunlight in shallow pools.
Snakelocks anemones
By scanning the torch across the pools it is possible to spot the anemones from some distance away.
Snakelocks anemones fluorescing. Seaweeds on the rock are also fluorescing red and pink.
We stand on the rocks and look into a large pool. Prawns, glowing blue under the UV torch, swim to and fro, intent on feeding. A common shrimp skitters across the sand. The green seaweeds glow bright red and the pink encrusting seaweed takes on a deeper pink-purple hue.
Exploring the pools as it gets dark.
We alternate between the normal torches and UV, finding sea scorpion fish, a rockling and even a young tompot blenny with its distinctive headgear. Irys finds a common blenny in a hole in the rock, lying still and breathing through its skin while it waits for the tide to return.
Sea scorpion fish – Taurus bubalis – hiding among the seaweed.
Hermit crabs run around the pools and some of the top shells glow pink under UV where their shell has worn away to reveal the mother of pearl layer below.
Taking a close look at an isopod at night. (Photo by Other Half).
Flying insects swarm around our head torches while bats dance in and out of the light. We tread carefully and stop still for long periods, looking into the water, enjoying the window into the animals’ lives while the waves splash against the rocks beyond us.
It’s fascinating to explore fluorescence. Anemones glow, stalked jellyfish not so much. Crabs and isopods stand out against the seaweeds in shades of blue and grey. A shell containing a hermit crab shines a bright orangey-red, probably due to micro-algae growing on it. In every pool, once you get your eye in, there are countless blue specks zipping about in dizzying circles, which must be copepods or similar small crustaceans that I would normally only see under the microscope.
At night, crabs often emerge from the water and cross the rocks. This green shore crab was carrying a limpet off to eat.
Green shore crab holding a limpet in its right pincer.
Normally it is the rising tide that brings an end to our rockpooling, but tonight it is tiredness that creeps up on us. Still buzzing from all that we have seen, we head home to bed. Behind us the rock pools seem quiet and deserted, but we know better; for the wildlife on the beach, the night is just beginning.
The sun is shining, the tide is going out and I’m wearing my ‘new’ blue sunglasses that I found in a rock pool last week. Junior and I are searching for signs of new life on the sheltered shore at Looe. Most of all, we are looking for cushion starfish eggs.
We aren’t the only ones out on the beach. Grey herons, egrets, oystercatchers, great black-backed gulls and crows, many with hungry nestlings to feed, are taking a keen interest in the pools and rocks. We give the birds plenty of space and settle ourselves by a mid-shore pool.
There is always lots going on here. Colonies of light-bulb sea squirts are sprouting up around the rocks, hermit crabs scuttle across the gravel and prawns swim over to see what we are doing – or perhaps to see if we are edible.
Light bulb sea squirts.
Under a rock adorned with a brilliant blue patch of Terpios fugax sponge, a rock goby is lying still, watching me through small eyes.
Terpios fugax – a blue sponge
Goby
Another goby close by, its head poking out from under a stone. There is no sign of any rock goby eggs, but as I check the underside of the rock, something glides along its surface.
Spot the fish
It’s hard to see what the tiny creature is. It looks as though it is changing colour as it moves, but this is because I am seeing straight through its body to the colours of the algae and sponges. After a few attempts, I manage to zoom in on the baby fish, which rests only for a few seconds at a time before zipping forward in a new direction.
The baby fish is very transparent.
This is probably a baby goby. As the summer goes on, many quiet mid-shore pools will hold large populations of tiny gobies and blennies.
The juvenile fish’s organs and spine can be seen clearly in its transparent body.
The cushion star Asterina gibbosa is a common rock pool starfish here in Cornwall, easily recognized by its puffy body and short, stiff, arms. These little starfish all start life as males and then become hermaphrodites (with both male and female organs) as they grow.
Unlike many other species of starfish, these cushion stars do not spawn into the plankton but lay a clutch of bright orange eggs. I sometimes find newly-laid eggs several times.
Cushion stars (Asterina gibbosa) laying eggs
When the eggs are developing, the curled-up legs of a baby starfish can just be seen.
Developing cushion star eggs.
This area of the beach seems to be a popular egg-laying site for the cushion starfish, so today I am hoping to fully developed or just-hatched eggs.
I search the pool, gently lifting a few stones before replacing them exactly as they were. This pool is crowded with St Piran’s and common hermit crabs of all sizes. The high population means that there is competition for shells. One St Piran’s hermit crab is occupying a very battered dog-whelk shell with half of the back missing – it’s better than nothing.
St Piran’s hermit crab in a broken dog whelk shell.
A Xantho hydrophiluscrab wanders past me. From the way her tail sticks out a little behind her shell, I can see that she must be carrying eggs. I take a quick look, keeping her in the water and cradling her to keep her eggs safe. The tiny black spots on the eggs show that they are near hatching. Under my camera I can see all the little eyes staring out.
Xantho hydrophilus crab – female with eggs. The feathery accessories around her tail keep the eggs in place.
When her eggs are ready to hatch, the crab will release them into the sea, flapping her tail to send them on their way. The baby crabs will swim in the plankton for a while before gradually changing into their final form and settling.
Xantho hydrophilus crab eggs looking ready to hatch
Finally, I come across a small patch of orange cushion star eggs under a rock. I crouch down and put my camera in the water. These eggs look a little different to others I have found. It takes me a moment to realise why: they have hatched!
Instead of eggs, I am looking at hundreds of minuscule orange cushion stars, all very gradually extending their little tube feet and beginning to move and explore.
The cushion starfish eggs have hatched. Asterina gibbosa juveniles.
Most of the cushion starfish babies are still piled up together in a huddle, but some are a few centimetres away from the crowd, already taking their first journey alone in the rock pool.
I am entranced. So much so, that I don’t notice that I am sitting in the water getting a wet bottom while I take photos. I could stay watching this forever, but I want to share it with Junior.
A bundle of newly-hatched baby cushion stars.
Junior goes through the same process as me, seeing the eggs and taking a few shots on his camera before realising what he is looking at. He’s seen most things in the rock pools by now so it takes something special to impress him. This is something very special.
Newly-hatched cushion starfish.
Cushion stars are lovely; baby cushion stars are pure magic. Once again, the rock pools have exceeded all our expectations. We will never know how things turn out for these particular baby starfish, but we may well meet some of them again as adults on our future visits to our local shore.
If you are visiting the beach this summer, be sure to rock pool responsibly and safely. Check the tides and leave everything as you found it. Read my top tips for successful rock pooling.
This website is a labour of much love and the content is available for free to everyone. My wonderful readers often ask if there is a way to support my work. You can now ‘buy me a coffee’ through my Ko-fi.uk page. (Just click donate and you can set the amount to pay by PayPal). Thank you!
My son has had the same spade since he was three. When I first agreed to let him loose with something bigger than himself with sharp metal on the end it was something of a risk. Since then, it has been his favourite possession, enjoying frenzied use on beaches all around the Cornwall and in all weathers, creating dams, pits, castles and ‘sand volcanoes’. The blade has been wobbling for some time now, but today Junior has plans for a tide fort at Millendreath, so we hope for the best.
Blue spade going strong in 2019 (age 8).
We cross the rocks towards the sandy beach, stopping on the way to explore the pools. Many of the seaweeds growing at the base of the rocks are covered in a dense thicket of Dynamena pumila hydroids.
Dynamena pumila hydroids (the yellow strands) on seaweed.
They look like pale plant stalks, each just a few centimetres long, but up close I can that each ‘stalk’ is made of a stack of downward-pointing triangle shapes.
Dynamena pumila up close – looking like a stack of tiny golden cups.
When they are submerged as the tide comes in, a circlet of delicate stinging tentacles will emerge from each side of every triangle to catch passing food. Hydroids are fascinating animals, and are also a favourite food of some other species, including sea slugs.
Among the hydroids are a few spots of jelly, just a few milimetres long. They are very hard to see, especially while the seaweed is stranded out of the water, but these are sea slugs. In places I find the hydroid stalks are entangled with a fine strand of white – the sea slug spawn.
A tiny Doto sea slug out of water – my fingertip is in the background for scale.
I try various ways to get the hydroids into water so that I can see the slugs better, but nothing works. I don’t want to harm any of the animals by removing them so I give up.
Trying and failing to take good photos of a Doto sea slug in situ.
Further down the beach towards the sea, the gulls are making a huge racket, screaming and splashing. Where the rocky gully we are in opens into a wide sandy pool, we come upon a scene of complete chaos. Scores of herring gulls and some greater black-backed gulls are jostling for space: some swimming on the pool, others flying down and yet more perched on the rocks all around. Many are dunking their heads in the water, reaching for something. There must be food here.
We try not to bother them but most of the birds fly up as we clamber over the last rocks to the beach. I take a quick look in the pool and find it is strewn with dead sand eels. There are so many that they have drifted into heaps against the rocks and some have tangled themselves into balls in their efforts to escape.
It’s sad to see so many dead sand eels but, for the gulls and other seabirds, it is a bonanza.
These mass strandings of sand eels happen sometimes. Perhaps it is the warm weather and low tide combining to starve them of oxygen as they hide in the sand, or perhaps a large shoal became trapped here and were an easy target for the seabirds. There is nothing to do but leave the gulls to their feasting.
There were hundreds of dead sand eels in this pool.
While Junior is shoveling sand with his dad, I return to the hydroids. After much searching, I find a slug that is only loosely attached to its prey and manage to wash it into a small tub. As soon as it is in the water, it transforms from a featureless blob into a magnificent structure of wobbling towers and waving rhinophores.
Doto sp. These slugs look magnificent in the water.
This is a Doto sea slug, but the species is not so clear. Most Doto slugs feed on very specific hydroids. My old books suggest Doto coronata can feed on Dynamena, but now it seems that they eat other things and that this is likely a different species, perhaps Doto onusta. Whatever it’s called, it is a true leader in the field of jelly architecture.
I have no idea what purpose the towering protrusions topped with dark spots fulfill – maybe camouflage, maybe just housing to its digestive organs, but they are incredible.
Doto sp. sea slug.
I find a sheltered pool where I can photograph and watch the little Doto for a while, before gently returning it to the exact same place I found it.
The dotty Doto slug exploring the pool.
Junior has just about finished his sand fort when his spade finally parts from the handle with a wet crunch. We lovingly assemble all the bits and make sure to pack them into our bags, hoping that we can somehow repair it later. We share stories of all the happy times Junior has enjoyed with his spade over the course of the last nine years. It feels like saying goodbye to a family member, but the tide is coming in and Junior perks up to defend his fort from the waves, standing atop the sand until the sea starts to flood his wellies.
Back at home, Other Half disappears into the garage and rummages for a while before emerging with the spade firmly fixed to a new shaft. Blue spade lives to build again!
After many days of getting drenched every time we step outside, Junior and I decide to make the most of the warmer weather and have a lazy day pootling about our local area. If everyone else is taking a holiday in Cornwall, so can we! The rocks between Plaidy and Millendreath are perfect for clambering and exploring, and I promise Junior a spot of wave jumping when we reach the sand beyond.
‘Slug alley’ at Millendreath
“I’ve found a blob,” Junior calls over to me.
I am kneeling among some seaweed at the top of a deep rocky gully. My head is almost pressed against the minute Dynamene pumila hydroids that grow on this seaweed, looking at what I’m sure is Doto sea slug spawn. “What kind of blob?” I ask.
“I think it’s a slug,” he says, and I’m up and at his side in a second.
The blob is bigger than I expect, almost like a small anemone on the rock. We stare at it closely, our heads touching. It looks as though it is tipped with blue.
“Oh my word,” I say. “I think you’ve done it.”
We hug and cheer and do a little slug dance, because every slug deserves a dance and this one is especially special. For weeks now, we have been looking for Antiopella cristata, a slug which ought to be found here but which I have never seen.
Taking great care not to harm the slug, we transfer it to a pot of seawater and watch it floof up.
The fully ‘floofed’ Antiopella cristata nudibranch sea slug.
The slug’s body is yellowish, but its back is covered in large waving cerata, each tipped in pale, frosted blue. The effect is like opening a geode to find tall, pointed blue crystals inside.
Close-up Antiopella cristata’s cerata remind me of peacock feathers.
We call the slug ‘Aunty Crystal’ to help remember its scientific name.
Antiopella cristata – or Aunty Crystal as we named this stunning sea slug.
We have named this gully ‘slug alley’ for a reason and plenty more creatures, slugs and others, are hiding on the tall, shady rock face. I find several bright red Rostanga rubra slugs munching on the red sponges.
The Rostranga rubra slug, which gets its incredible colour from the sponges it eats.
A tiny ghost-white slug has been laying its eggs nearby. In the water it takes on a frilly appearance, making it look ever more spectral.
Goniodoris nodosa, looking frilly and ghost-like.
Sea cucumbers adore this area and are to be found everywhere, with their bodies hidden in holes in the rock and just their black and yellow mouths protruding. The two main species I see are Pawsonia saxicola and Aslia lefevrei.
Sea cucumber at Millendreath.
When submerged, they will open a wide fuzz of frilly tentacles to feed.
We clamber over the rocks onto the sand, helping a stranded rockling back into a pool on the way, and splash in the waves for a while.
This rockling had ended up out of the water at low tide, so we helped it back into a pool.
A couple of shells roll past my feet, tumbled by the waves over the silty sand. I make a quick grab for them and, sure enough, they both contain hermit crabs. At low tide, I occasionally find this species here, easily recognised by its enormously long left claw. These crabs are both south-clawed hermit crabs, also known by their gladiatorial sounding scientific name, Diogenes pugilator.
Diogenes pugilator, the south-clawed hermit crab.
They are ready for battle, almost falling out their shells in their attempts to dislodge my grip, unaware that I am saving them from the herring gulls that are lurking at the water’s edge.
The south-clawed hermit crab has long hairs on its antennae.
Junior and I kneel at the edge of a sandy pool and pop the hermit crabs in. We watch one emerge without hesitation. The tips of its claws come first, then the stalked eyes and finally its long hairy antennae. The hermit crab hoists its shell up and runs a few paces.
With a furtive glance about it, the crab swings its vast left claw inwards, shoveling sand into a pile while simultaneously flicking the sand over its back with its little right claw. Grains of sand are flung up through the water and by the time they have settled, only the back of the shell and the tops of the hermit crab’s eyes are visible. It is buried out of sight.
We take the hermit crabs back to the sea, leave them as far out as possible – safe from predators – and carry on wave hopping until the tide turns, when we too must head for home.
Here’s a little video of this week’s highlights from the Cornish rock pools. Sit back and enjoy!
Who doesn’t need a week off at the moment? Whether you’re visiting your local beach or holidaying in Cornwall, rock pooling is a free and fun experience for all the family.
Read on for links to events, rock pooling tips and my guide to what you might find.
Organised rock pooling events are perfect for learning about marine wildlife with the experts. Due to current restrictions, booking is essential for most activities and plans may change. At the time of writing, the following groups and organisations are planning events in the half term:
If you’re not able to attend an event, don’t worry. It’s easy to rock pool safely and to look after the wildlife with a little preparation.
ROCK POOLING TIPS
All you need for successful rock pooling is a pair of wellies or sturdy shoes and a little patience. There are many fascinating species to see, so go slowly, look carefully, leave everything as you found it and have fun!
The European 3-spot cowrie (Trivia monacha)
St Piran’s Hermit Crab at Hannafore, Looe
A colourful Xantho pilipes crab.
A dahlia anemone.
Watching fish at Kynance Cove
Green shore urchin, Hannafore, Looe
Learning about a spiny starfish at a Wildlife Watch event
Junior getting to know our wrasse-friend before we put it back
A juvenile turbot at Lundy Bay
Drying off in the sunshine after rock pooling at Port Nadler, near Looe.
Plaidy near Looe
Just one more rock… exploring the Cornish rock pools
Flat periwinkles and other shells washed up on Looe Beach
Montagu’s blenny with its distinctive head crest
Painted top shell.
Always check the tide times, stay clear of cliffs and waves and dress for the weather.
Nets can harm delicate sea creatures so are best left at home. A bucket or tub is ideal if you want to scoop up an animal to look at, but be sure to put it back.
Why not finish up with a beach clean to help look after the wildlife?
The choice is endless! Cornwall has over 300 beaches and they are all fantastic. Any beach with rock pools will have crabs, snails, anemones, fish and more.
Find out about some of my favourite rock pooling beaches here.
WHAT TO SEE
May and June are fabulous rock pooling months. The pools are bursting with new life from baby fish to brightly coloured seaweeds and stunning starfish.
Sit quietly and look closely at the pools to watch prawns, crabs and sea snails going about their business. Gently lift seaweed and look under stones to reveal the secret hiding places underneath (be sure to put them back as you found them).
Here are some of my favourite treasures to find in the pools …
Cushion Stars
These puffy little starfish are common in the pools. Did you know that they can re-grow their arms?
Shannies
The common blenny (or shanny) is perfectly adapted to shore life and can even breathe through its skin when out of the water. It also has a goofy smile.
Sea lemons
Sea lemons a type of sea slug. They eat sponges and breathe through the frilly gills on their backs.
Green Shore Crabs
Green shore crabs can survive in lots of different conditions and can eat almost anything – even each other. This female has eggs under her tail.
Common Prawns
Prawns are curious and will often swim over to investigate anything new in their pool. You can see right through their bodies!
Strawberry anemones
Strawberry anemones are red with yellow flecks, just like a strawberry. Their tentacles are packed with stinging cells to catch their prey.
Star Ascidians
Star ascidians might look like flowers but they are simple animals called sea squirts. They form colonies – each ‘petal’ of the flower shapes is an individual animal. They can be yellow, blue, purple, red or white.
Flat Periwinkles
Flat periwinkles feed on seaweed and come in lots of colours. Look out for their eggs on the seaweed – they look like little circles of jelly.
These are just a few of the creatures you might find. Discover more with my guides to the wildlife in the rock pools and my blog.
Happy rock pooling! Be sure to get in touch to let me know what you find this half-term.
It is going to be hard to top our last, sea slug filled rock pooling session at this beach, but we can’t resist popping back for another look. This time, we have reinforcements!
I have the best friends in the world. Not only do they obsess about rock pool creatures but Sarah has picked up pasties for Other Half and me, and Charlotte arrives bearing a gift of homemade cake. As this is the fourth day in a row of rockpooling in the biting cold, comfort food is going to be essential. Sarah’s partner is gallantly entertaining the kids for the day and we’re joined by our film maker friend, Greg who is looking for sea slugs – it’s the sort of mission we can all buy into.
Returning to a beach we visited only a few days before is a bit like a memory game: if we can just find the right pools and rocks, we should be able to rediscover some favourite creatures. Sure enough, Greg is rewarded for his enthusiasm by coming across what is probably the same fabulously colourful Facelina auriculata slug we found before.
Meanwhile, Sarah, Charlotte, Other Half and I are on a mission to record the incredible diversity of species at this site.
Anthopleura ballii anemone
There is so much here, it is hard to know where to start. I make the most of my waders and explore the pools and overhangs which would otherwise overtop my wellies. Some species are unusually common here, like the Anthopleura ballii anemone. Its brown and white speckled pattern gives it something of the look of a 1970s pub carpet. The distinctive lines of crimson spots on its column make it instantly recognisable.
Among the sand are occasional pieces of maerl, a red encrusting seaweed with a calcareous skeleton which forms bright pink living sculptures. Offshore in this area, these slow-growing structures can cover the seabed, building up in layers to provide shelter for many small creatures and young fish. Nationally and internationally such maerl beds are scarce.
The new spring growth of the rainbow wrack is everywhere, sprouting into great bushes of turquoise and iridescent greens and blues that seem to change constantly. Around their thick, branching forms, dense colonies of encrusting animals form and I spend a long time staring into their tiny worlds of densely packed sponges, starry sea squirts, feathery hydroids and busy crustaceans.
Rainbow wrack
Sarah finds our little Palio nothus slug, still powering through the same giant goby eggs. I spot another, larger one nearby and Charlotte discovers yet another near the end of our session. None of us had seen this species before this week and now they are everywhere.
Palio nothus among the goby eggs
Another Palio nothus
We seemed destined to find slugs this week. All of us keep spotting more and I can hardly keep up. The largest is this great grey sea slug, Aeolidia filomenae, which is hunting for anemones under a rock. Judging by its size and pink colour, it has been feeding well.
Great grey sea slug, Aeolidia filomena, hanging upside down under a rock.
Among the thick, velvety branches of the codium seaweed there are a few solar powered sea slugs, Elysia viridis. These remarkable little slugs feed on the seaweed and retain the plant’s chloroplasts in their bodies. The chloroplasts carry on photosynthesising and provide the slug with energy.
Codium seaweed
Elysia viridis – the solar powered sea slug.
While I am exploring the seaweed, an isopod swims over and rests for a moment on my finger. These little crustaceans are relatives of woodlice and come in all sorts of shapes and sizes. This one is a Dynamene bidentata, so-called because of the two little prongs on its back (bidentata means two-toothed).
Dynamene bidentata, an isopod.
The slugfest continues apace, with one of my favourites. Limacia clavigera, the orange-clubbed sea slug, is a species I often find, but it’s always a delight. Like many sea slugs, it looks like it has been let loose in a dressing up box. Its slender white body is splendidly adorned with long yellow and orange appendages, sticking out in every direction. Greg finds one so large that it looks like two slugs.
Limacia clavigera, the orange-clubbed sea slug.
The tide is turning. I am so cold I should probably have left a while ago. I have to shake my hands and windmill my arms around my head to try to restore feeling in my frozen fingers, but I can’t bear to miss a thing.
We see plenty of sea hares and their spawn, and count around a dozen Geitodoris planata slugs, but some tiny finds are the most exciting of all.
A tangle of sea hare spawn.
Sarah calls me over. She has located some possible slugs on a rock, but they are so small she is doubting herself. Bracing myself, I put my hands in the water once again.
It’s hard to operate the buttons on my camera and hold it steady enough, but I’m sure she is right that there is something here. There is a faint pale mark on the rock that could be spawn and something alongside it that is just a speck.
The image takes shape on my screen. There are two slugs and it looks as though they are busy spawning. Their chunky cerata are prettily speckled with white and they have red lines on their heads. There are lots of similar species, but I’m fairly sure these are Trinchesia foliata (a name I remember as the ‘three-cheese foliage slug’).
The two Trinchesia foliata slugs with their white spawn in the background.
You need to look carefully to spot slugs! The Trinchesia foliata slugs with a finger in shot for scale.
I have only found this species once before in Looe, so it’s fantastic to see two spawning like this.
Trinchesia foliata
Charlotte calls me to look at a slug she has found and doesn’t recognise. It’s another tiny one with a colour pattern I have never seen before. The tide is coming in fast now and the wind is picking up, making it hard to find a sheltered patch of water to observe. I kneel in a pool and place the slug on a small stone to view it better.
Favorinus branchialis juvenile slug.
Each long cerata on the slug’s back is decorated with a red spot at the tip, like a cherry on the cake. It has a wide moustache-like pair of oral tentacles on its head as well as tall browny-orange rhinophores with white tips. It is these that make me think it might be a Favorinus branchialis, but it seems to lack the distinctive onion-dome bulges that I associate with that species.
It is only when I get the photos home and onto a large screen that I can see all the features, including the the slight curve in the rhinophores and decide that it is F. branchialis after all. The bulges are less pronounced in juveniles than in the adult slugs. This species is often found feeding on the eggs of other sea slugs.
Favorinus branchialis
While Charlotte returns the slug to where she found it, I take a look at a stalked jellyfish that Other Half has spotted on some sea grass. The jellyfish and the frond of seagrass are swaying in the current, making it hard to take a photo.
Haliclystus octoradiatus stalked jellyfish on seagrass.
Back in Sarah’s pool I discover even more slugs. A ‘feathered Bertha’, Berthella plumula, is under one rock, while another Limacia clavigera is feeding near the pair of Trinchesia foliata. Charlotte finds another little Palio nothus slug.
The tide is gushing into the lagoon, flowing around the spot where Other Half is still trying to photograph the stalked jellyfish. After a couple more minute he gives up and wades out, sitting on the rocks to take off his boots and wring out his socks.
Greg spots a yellow blob, which I find almost impossible to focus on, probably because my fingers now have no feeling at all. The sandy-looking spots on this sea slug show that it is a Doris ocelligera. This is a species that was very rarely recorded around our coasts in the past, but which I have found frequently in recent years, possibly due to warming waters.
Doris ocelligera slug near Falmouth.
With the sea lapping at our heels, we finally admit defeat. I’m not a great fan of tea, but I have never been more grateful to the inventor of the thermos flask than now, sitting at the top of the beach, cradling my hot drink and feeling my fingers gradually become reacquainted with the rest of my body.
As always, I have seen new things today and learned more about the creatures on the shore from glimpsing their world. It is incredible to me that anything can survive here and yet there is enormous richness in this ecosystem. Charlotte and I will make sure that everything we have found is recorded with our local records centre.
Recording the species we have seen helps to monitor changes in the wildlife over time and to inform conservation projects and policies. Online systems such as ORKS and i-Naturalist make it easy for anyone to submit their finds.
It will be another month before the tides are this good again – time that I will use wisely warming up and eating cake!
Pheasant shell on codium seaweed.
Yellow star ascidian with patches of the non-native red-ripple bryozoan Watersipora subatra.
Finding a sea slug is always a moment of joy. I can’t imagine ever losing the excitement of spotting a minuscule blob that might just be something and realising that it is moving, unfurling, becoming spectacular. There are so many species, that I have plenty yet to discover as well as many old acquaintances to renew.
Limacia clavigera – the orange-clubbed sea slug. Near Falmouth. Out of the water, these slugs are shapeless blobs.
The oystercatchers are unusually quiet, huddling between the rocks in the distance and I’m glad of my waders to keep the worst of the north wind off. Conditions could be better, but with two households of keen rock poolers on the beach today, all trussed up in enough layers for an Arctic expedition, we feel sure that good things will happen. Junior and his friends let us adults get a head start while they chat after a long time apart, but they’ll soon join us when we uncover something interesting. Sure enough, just minutes into our explorations, the shout of ‘slug’ goes up.
Other Half, who was just saying that he always looks for sea slugs but never finds them has found one. He beams and points it out; I have to follow his finger to see it among the pink coralline seaweed.
Not only has he found a slug, it is an absolute beauty.
Other Half’s wonderfully orange Aeolidiella alderi – the white-ruffed slug.
At first I think this is a species that I haven’t seen before. The slug’s body and the rhinophores protruding from its head are an intense orange. The dense hair-like cerata on its back are mostly patterned in speckled grey and orange, except for a bright white row of cerata immediately behind the slug’s head, forming a pretty white ruff around its ‘neck’.
Among the pink algae, the slug is surprisingly well camouflaged.
It is this white collar which makes me realise that the slug is likely to be a species which is usually far less colourful, Aeolidiella alderi. This slender slug feeds on anemones, and is particularly fond of daisy anemones. Like some other Aeolid slugs, A. alderi takes in the colour from its food, so it looks like this little slug has been feasting on something orange.
Aeolidiella alderi.
I have barely started to look at the A. alderi slug under my camera when our friends shout, ‘Slug!’ I hurry across the rocks as fast as my waders will take me, looking and feeling rather like a lumbering green Teletubby and not caring one bit. The day has started as we hope it will go on.
We position ourselves around the minute blob and angle the rock it is on so it is a little deeper in the pool. Like most slugs, it looks like a tiny streak of jelly when it is out of the water, but once submerged its back fluffs into long star-studded cerata and enormously long moustache-like tentacles curve out from its head.
The wide oral tentacles on this Facelina annulicornis remind me of a circus ringleader’s moustache.
The ringed rhinophores on this slug’s head look like a pair of mini helter-skelters, waving at my camera as the slug advances towards me. A pair of black eyes stares up into my lens.
Facelina annulicornis.
The slug is so small that I’m not entirely sure of the species until I see the photos on a bigger screen back at home. The little star-spots all over its body are a giveaway. This is Facelina annulicornis, which I call the ‘starry unicorn slug’ to help me remember the scientific name.
Facelina annulicornis – or the ‘starry unicorn slug’ as I call it.
Back on the beach, I take our friends to see Other Half’s little orange slug and we explore the pool further. To my amazement, the very next stone I check has an intense spot of purple on it, like a gleaming amethyst. This can only be another slug.
I place the rock gently under the water and the slug fluffs up in an instant, forming a ball of intensely coloured cerata. The colour is so bright that I expect it to be an Edmundsella pedata, but as it stretches out its body I can see that the cerata are vivid blue, red and white, a Facelina auriculata.
The exceptionally brightly coloured Facelina auriculata.
This is the most incredibly coloured one I have ever seen and my camera cannot fully capture how bright it is. The slug is so captivating that I only realise there is a second, less colourful, slug on the rock when it photobombs its companion. This is likely to be a mating pair, although there is no sign of spawn as yet.
The second slug is larger, but I almost miss it because the first Facelina auriculata is so strikingly coloured.
By now, the children have joined us, keen to see what all the excitement is about. Junior recognizes the ‘patriotic sea slug’, as we call the Facelina auriculata (in honour of the many countries that have red, white and blue flags), but the colours make him gasp with amazement. He sets to with his camera, trying to capture every angle.
One of Junior’s lovely photos of Facelina auriculata.
As the tide rolls further out, the pools seem to stretch forever in every direction and I’m torn as to where to go next. Every pool is full of possibility and I cannot visit them all before the sea returns.
I decide to make the most of my waders, slooshing out to the edge of the sea, through shallows packed with rainbow wrack adorned with the mermaid’s purse egg cases of greater spotted catsharks (Scyliorhinus stellaris).
A catshark eggcase (Scyliorhinus stellaris)
There are flatworms galore, their clusters of eyespots seeing the world in ways I struggle to imagine. A variegated scallop spots me through the many eyes dotted around its part-open shells and decides to move to safety, slamming its shell shut to propel itself.
Urchins extend their tube feet in their strange dance, curving and twisting between their purple-tipped spines.
One of our friends finds a fully-grown spider crab, sheltering beside a rock, wonderfully camouflaged against the shell sand. We leave it undisturbed and well covered in seaweed to keep it safe from the marauding gulls.
The spider crab, hiding away.
Our other friend signals to me from beyond the rock line. She is performing our special arm-waving dance, as invented by Junior. She must have found a Discodoris slug (Geitodoris planata).
The pair of Geitodoris planata slugs. They can make their bodies almost flat on the rock, with only their rhinophores and their feathery gills standing up.
These unpretentious brown pancake-flat slugs don’t have any of the bling of the other nudibranch slugs we’ve seen today but looks aren’t everything. The Geitodoris planata’s secret weapon are acid glands, forming white stars on the slug’s sides. This is a formidable and fascinating slug.
Geitodoris planata. The white patches on its back are acid glands.
Incredibly, our slug finds keep on coming. Close by is a Berthella plumula, which we call the ‘feathered Bertha’. This striking yellow slug can also produce acid if it is disturbed and, weirdly for a slug, has an internal shell, visible as a dark patch in the middle of its back.
Berthella plumula with its tentacles extended, exploring the rock.
Another yellow spot on the rock turns into this fabulous Limacia clavigera slug as soon as I put it in water. I take a few photos before carefully returning it to its hideaway.
Limacia clavigera, the orange clubbed sea slug.
The tide is coming in and the raw wind has taken its toll on my hands. I stuff my frozen fingers down the neck of my jumper, but they are still painful and numb from plunging repeatedly into the water. A sensible person would give up before frostbite sets in, but I’m not that sort of person… there might still be slugs to find. The kids are not so daft: they have wandered back to the top of the beach to start on the picnic lunch.
The rocks are full of animal life and seaweed. A yellow-ringed sea squirt (Ciona intestinalis) on a rock encrusted with sponges.
As the tide moves up behind us we explore the mid shore, hoping to find goby eggs or clingfish eggs and the slugs that eat them. It’s still a bit early in the season, but we find a few patches of yellow clingfish eggs.
Clingfish eggs.
Eventually, hauling up a rock that feels as big as myself, I spot some capsule-shaped eggs on the underside. These are larger than the rock goby eggs I’ve seen this week, so they could belong to a giant goby. Some of the eggs are empty and others are well-developed, the baby fish looking out at us with silvery eyes. Taking great care not to disturb them, we scan the rock.
Goby eggs.
Seeing no sign of slugs, I use my camera to look more closely. At first I find nothing, but spotting something tiny and dark I zoom in. My hands are struggling to press buttons, but I convince myself this is something. It seems to move a little.
All of a sudden I have it in focus, although it is half-hidden between the eggs. This is a slug quite unlike the others we have seen today. Its body is compact, lumpy and camouflage green. On its head two wonderfully tall rhinophores stick up, poking above the eggs like periscopes. If the army designed slugs, they would probably look a bit like this.
Palio nothus – looking like a stylish armoured car.
I’m so thrilled I almost keel over backwards as I try to balance my camera and keep the stone steady. This is a Palio nothus; the very first slug of this species I’ve ever found. It is probably feeding on tiny animals called bryozoans on the rock rather than the eggs. It’s barely 5mm long, probably less, and almost impossible to photograph properly with my seized up fingers, but I couldn’t be happier.
Palio nothus among the goby eggs.
This beach is amazing and the slugs are just what I hoped to see, but the best thing of all is to finally share the experience again with amazing friends and my wonderful family. It will take me all day and night to thaw out but I couldn’t care less. This is my happy place.
Rock pooling is a wonderful way to see the wildlife if it is done carefully. If you are heading to the shore, remember to leave the stones, seaweed and animals exactly as you found them. Take nothing with you and leave nothing behind. There are lots of rockpooling tips on this site to help you rockpool safely and sustainably and identify your finds.
For everyone who loves Cornwall's rock pools. Information about great beaches, marine wildlife and conservation.
Cornish Rock Pools 