Category Archives: Molluscs

Rock Pooling at Lizard Point: Cowries, Sea Slugs and a Saffron Bun

It’s not exactly tropical, but we’re as far south as you can go on the UK mainland. The sun is shining and the clear water gives us a perfect view into the pools. After a morning of geological exploration at Kynance Cove, my family are treating me to some low tide rock pooling here at Lizard Point.

Rock pools at Lizard Point

Apart from the chatter of seabirds and a distant hum of voices from the cafés perched on the cliffs, the beach is still, expectantly waiting for the tide to turn. Out in the bay, a bull grey seal rests upright in the water. He is ‘bottling’, his broad snout raised to the sun, keeping half a sleepy eye on the female that is snoozing closer to the shore. There are no boats here to disturb the seals, so they nap peacefully on and on, barely moving with the gentle rise of the swell.

The colours in the pools are as vivid as a royal procession. Neon green snakelocks anemones jostle for space with dusky pink coralline algae, yellow sea squirts and iridescent blue seaweed. Tiny rainbows play across the rocks.

A colourful pool at Lizard Point – Snakelocks anemone

Looking closer, we begin to notice other rock pool wildlife that is less keen to stand out, adopting the same bold colours as the seaweeds and encrusting animals to hide from predators. Tiny Elysia viridis sea slugs are everywhere, but they match the deep green of the codium seaweed perfectly.

Elysia viridis on codium seaweed.

These are the ‘solar powered’ sea slugs. They retain the seaweed’s chloroplasts, which carry on photosynthesizing in their bodies, making glucose to supplement the slugs’ diet.

Elysia viridis sea slug stretching out to make the most of the sunlight. Spot the second slug!

A variety of animals are resplendent in shocking pinks and oranges, which allow them to disappear among rocks adorned in pink paint seaweed and forests of other red seaweeds. A European 3-spot cowrie (Trivia monacha) is roaming the rocks looking for sea squirts to eat.

Trivia monacha – the European 3-spot cowrie at Lizard Point. It feeds on sea squirts like the blue star ascidian to the left of the photo.

With its sunset-orange proboscis fully extended and its spotty mantle draped over most of its shell like a (fake) fur cape, it has the air of a glamorous Dalek.

European 3-spot cowrie (Trivia monacha) doing a Dalek impression

Not to be outdone by the molluscs, there are some stunning worms in the pools. My favourite is this syllid worm, gliding across the rock with its enormously long, whisker-like appendages stretching and curling in all directions at once.

Syllid worm. Amblyosyllis sp. looking spectacular. Lizard Point, Cornwall.

This feels like a spot that sea slugs should like. There is a variety of food on offer and no shortage of hiding places among the pools and boulders. Sure enough, under one rock I find two species hanging out together. They look like friends, but they are on separate missions. The great grey sea slug (Aeolidia filomenae) feeds on anemones, while the Berthella plumula – or feathered Bertha as I like to call it – eats sea squirts or sponges.

A quick hello in passing – Great grey sea slug (Aeolidia filomenae) and Berthella plumula sea slugs.

Junior, who excels at gathering people to look at things, has collected up an excited young boy and his grandfather to show them the pools. We all find things to show them – solar powered sea slugs, hermit crabs and a stalked jellyfish. While Junior is explaining barnacles to his fascinated audience, I wander down the shore, thinking I might find a starfish for him to show his new friend.

Stalked jellyfish (Haliclystus octoradiatus) on codium seaweed at Lizard, Cornwall. Photo by Cornish Rock Pools Junior

Sheltering under a small stone is a neat five-armed cushion star, but close to it, even more excitingly, there is a slender little Aeolidiella sp. sea slug.

This slug looked a little different: Aeolidiella glauca

Aeolid slugs vary in colour depending on what they have eaten, but there is something unusual about this one that I can’t place. It has a bit of a white ruff behind its head, but I’m not convinced it is the white-ruffed sea slug (Aeolidiella alderi) that I frequently see.

Aelolidiella alderi (pictured near Falmouth) is the more common species locally. It is often white or grey, but can take on bright colours like this after eating anemones.

I take some photos. Zooming in, I soon ‘spot’ the difference; the difference is the spots! There are tiny white flecks on the slug’s body. I take photos in the pool before ensuring it is returned safely back under its stone.

Aeolidiella glauca sea slug, Lizard, Cornwall

Despite my rush to identify the slug (which I suspect is an Aeolidiella glauca) there are even more important things to do on the way home: like stopping for a saffron bun and ice creams at Roskilly’s, and visiting friends in Gweek.

Thanks to the wonders of expert Facebook groups and also the brilliantly helpful David Fenwick of Aphotomarine, I have confirmation the same day. Aeolidiella glauca has occasionally been recorded in this area before, but it’s a first for me. It may be more common in northern waters, but marine creatures rarely follow the rules.  There are surprises everywhere and that is exactly what makes rock pooling so fabulous.

Another lovely little find: Lamellaria latens (gastropod mollusc) at Lizard Point
Dahlia anemone at Lizard Point, Cornwall
Gem anemone. Lizard Point, Cornwall.

Whatever the weather, 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 page. (Just click donate and you can set the amount to pay by PayPal). Thank you!

Christmas Rock Pool Catch-up

As you may have noticed, blog writing has been relegated to my ‘to do dreckly’ list for a couple of months now. In September, I unexpectedly started a job that I didn’t know I’d applied for and my photos of rock pooling trips, including this day at Prisk Cove, have been piling up ever since. It’s time for a catch-up!

A swimming variegated scallop was one of the highlights of this short video I put together at Prisk Cove this autumn.

For once, the gales and mizzle held off for our visit to Prisk Cove, making it an ideal day for sitting by the pools and staring. The longer I looked the more I discovered.

This Aeolidiella alderi sea slug had recently munched its way through a Daisy anemone, turning the cerata on its back from white to a deep, speckled brown. It is sometimes called the ‘white-ruffed’ slug due to the paler cerata that form a smart collar behind its head.

Aeolidiella alderi – the white-ruffed sea slug

Finding a nudibranch sea slug made an auspicious start to the day, and there were plenty more discoveries in store. Many of the tunicate sea squirts I find on the shore are dull brown, but this Ascidia mentula was an explosion of colour.

Ascidia mentula
Up close, the Ascidia mentula sea squirt looks like a riotous display of tiny red fireworks

Nearby, a chiton nestled among the barnacles, moving very slightly as I watched. These unassuming little molluscs have changed very little since the Devonian period. You have to look closely to appreciate their varied patterns. There are several species commonly found on our shores and some – like this one – have clusters of bristles fringing their armoured plates.

Bristly chiton
Bristly chiton

Flatworms are far more exciting to watch than chitons. They are speedy for their size, flowing seamlessly over rock and engulfing any obstacles they meet.

This remarkably bright flatworm is a Cycloporus papillosus. I mostly see them in shades of star-studded blue, but this one has other ideas. They vary in colour to match their equally resplendent prey, the star ascidian sea squirt.

Caught crossing the rock in search of new food supplies, this flatworm was easy to spot. Once it is on a sea squirt, it will become almost invisible.

Cycloporus paplillosus flatworm, normally found on star ascidian sea squirts.
The colourful Cycloporus papillosus flatworm lives on star ascidian sea squirts like these.

Rocky overhangs are my happy place. They’re a kind of lucky dip with fascinating creatures hiding in every single one. I wouldn’t advise putting a hand in an overhang as there’s almost always a crab lurking at the back, but it’s worth going through the contortions required to obtain a good view of what lies within. This spiny starfish, however, wouldn’t win any games of hide-and-seek.

Spiny starfish
Always watch your fingers when there are velvet swimming crabs about. This one had especially blue claws.

Unlike the starfish, my next find was a master of disguise, hugging the rock and changing colour to match it. Only the googly eyes and a tiny fluttering fin gave this topknot flatfish away.

Topknot checking out my camera
Pressed against the rock, the topknot is almost invisible.
Topknot flatfish swimming.

Among boulders encrusted in colourful sponges, I was delighted to find my favourite slug: “Discodoris” – the Geitodoris planata. This one was busy tucking into the sponges and sported plenty of acid glands to ward off any would-be predators, visible as white patches on the slug’s back.

Geitodoris planata enjoying a feast of sponges.

Tortoiseshell limpets can go unnoticed due to their diminutive size, but they have one of the prettiest shells on our shores. This one, nestling among the pink seaweeds, was a perfect burst of pink and blue.

Tortoiseshell limpet Tectura virginea

I always tell people that they should go slowly and look closely to see and appreciate wildlife. It works every time and is good advice for life in general, yet it’s advice I sometimes forget myself. In my haste to find the next thing, I can easily miss what is in front of me.

This quiet, meandering day at Prisk Cove, was a rare chance to truly stop and look, to watch animals doing their own thing. From the mysid prawns flocking around the snakelocks anemones to the way the green shore urchins had arranged their shelters of seaweed, pebbles and shells, there were endless insights into rockpool life. If the tide hadn’t come in, I would happily have stayed for many hours, staring into those perfect pools.

Nadelik lowen! Merry Christmas! Wishing you a happy and restful time.

Mysid prawn hovering over a snakelocks anemone
“The urchin’s got his hat on…” – Green shore urchin using a limpet shell for shelter.

Whatever the weather, 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 page. (Just click donate and you can set the amount to pay by PayPal). Thank you!

Slugtastic Rock Pooling near Falmouth

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.

Meeting up and staying apart in the rock pools

When I’m sitting here writing my blog in the evening, with the cat snoring gently beside me, I find it hard to imagine that people anywhere in the world might be reading about my finds the next day. So, it’s always lovely to receive messages from people who follow the blog and share my passion for our rock pool wildlife. It’s especially surprising to me that these include many people I’ve never met and that some of my readers even live beyond the Tamar!

With the days beginning to draw in and with all normal group activities off due to Covid, making connections with others is more important than ever. When I heard from a couple of keen naturalists and Shoresearchers planning a trip to Cornwall, I thought it could be fun to head out on the shore together with my family. I couldn’t have been more right!

You know someone is a good person when they like finding slugs. Within minutes of meeting our new friends on Millendreath beach near Looe, we had established that slugs were top of their wishlist of things to find. I led the way to “slug alley”, a deep gully between the rocks where I often find sea slugs feeding on the sponges, squirts, bryozoans and hydroids that line the dripping overhangs.

We advance in our family groups, keeping several metres apart, pointing at interesting creatures, giving directions then backing away. By this stage in the pandemic, we’re all confident in these new dance steps.

Botryllus leachii colonial sea squirts

Large patches of colonial sea squirts smooth over the rocky surfaces, providing not just striking colours and patterns but food for many animals that predate them. We find both the European three-spot cowrie and the Arctic cowrie happily gorging themselves on this beautiful feast.

A cowrie on the search for sea squirts to eat.

A brown spot among the squirts and barnacles catches my eye. Although the colours blend in perfectly, it looks different from its surrounds. I gently touch it and it comes away. In a seawater-filled petri dish it rapidly transforms itself, puffing up, elongating and sprouting feathery gills and tall rhinophores. There’s no doubt about it, we have our first slug. My excitement is as great as that of our new friends – this is a species I have never seen before.

Goniodoris castanea exploring the petri dish.

We take turns to examine the slug and take photos. As soon as it is under my camera, which shows far more detail than I can make out with the naked eye, I recognise it from my books (yes, I browse slug books for fun). It’s my first Goniodoris castanea. Castanea means chestnut and the slug’s autumnal mottling of red, brown and white hues make seems a perfect fit with the oncoming season.

Goniodoris castanea showing off its beautiful autumnal colours.
Goniodoris castanea

While our friends marvel at the slug, Junior makes another exciting find. He knows what it is just by the purplish tips of the arms protruding from under the rock. “Spiny starfish!” he calls. We carefully move it out to take a look and it’s a monster. Our starfish has clearly found plenty to eat in this area. Although we regularly see them on the shore here, spiny starfish aren’t found in rockpools in some other parts of the country and this is another new species for our visitors.

I forgot to take photos of the spiny starfish due to my excitement over the slugs – but here’s a pic of one we found on an earlier expedition to Millendreath.

We edge ever outwards with the tide. Although we can hear the shouts of holidaymakers playing in the waves on the beach beyond the rocks, no one else ventures into our magical gully where startled sand eels zip across the surface of the water like skimming stones and velvet swimming crabs scuttle across the seabed then bury themselves in the sand, leaving only their red eyes visible.

A lurking velvet swimming crab.

Some of the rocks are fringed with a dense covering of brown seaweeds. Toothed wrack and kelp compete for space here and clinging to this forest, mossy bryozoans and delicate hydroids thrive, creating a perfect habitat for isopods and slugs. Some of the seaweeds have crescents of white jelly scattered among their fronds. These are sea slug eggs but it takes me some time to find the slug itself, which is smaller than its spawn and decorated with bright yellow and black which somehow make it hard to see.

Sea slug spawn…. now to find the slugs.

These pretty little slugs were, until very recently, known as Polycera quadrilineata. Scientists have now discovered that there are two separate species and the ones we see here, which sometimes have black lines and spots, are now called Polycera norvegica.

Polycera norvegica feeding on bryozoans.

In the moving seaweed, it’s hard to take clear photos and the tide is, of course, coming in just as I’m trying to position the camera in water that’s already waist deep, but we are all content just to be here, together but apart, sharing this experience of encountering incredible creatures.

Polycera norvegica.
Pair of Polycera norvegica sea slugs with the edge of a fingernail in shot showing just how tiny these stunning little creatures are!

These are strange times for everyone, but finding ways to come together and enjoy nature is what makes the world go round (for me at least). Thanks to our new friends for making it a fabulous day. Happy rock pooling!

This time of year, the kelp is studded with blue-rayed limpets – always a joy to see.
Brown sea cucumber – Aslia lefevrei.

The Surprising Mini-World of Rock Pool Insects

If my blog posts have seemed a bit thin on the ground the last few months, it’s fair to put the blame on Atiyah, Brendan, Ciara and Dennis.

Even on the good days the lighting and conditions have been less than ideal so, to make the best of a mediocre tide, I enlisted the help of Other Half. Together, we could look under the sort of rock I usually see but leave alone, knowing it weighs far more than I do.

This short video shows you some of the animals living there…. read on to find out more.

Other Half was pleased with the strawberry anemones, which were enormously plump with all their tentacles retracted.

Strawberry anemone
Strawberry anemone

Under a carefully constructed shelter made of small stones and pieces of kelp we could also see the purple-tipped spines of a green shore urchin. Among its many disc-topped tube feet, a long polychaete worm was exploring.

Green shore urchin
Green shore urchin

What drew my eye most, though, were the holes in the rock. These were scattered across the surface of the rock and about the circumference of a pencil. I caught the tiniest glimpse of movement as I looked into one of them.

Piddock holes underneath the boulder.

If I were the BBC Natural History Unit, I’d have filmed inside with an endoscope or transported the rock to deeper water so I could photograph the gaping shells emerging to feed.  Instead, you will have to take my word for it that there were piddocks in those holes!

Piddocks are bivalve molluscs (clam shells), which burrow into the rock and spend their entire lives in their holes.

A rock with this many cracks and holes in it is bound to contain some good hiding places for other animals and also some air pockets, which enable some of our most unlikely rock pool wildlife to survive being submerged twice a day. Some insects and other arthropods that breathe air live here, but you have to be patient to see them.

I settled down with my camera and before long, the first waggling antennae of a springtail poked over the rim.

The end of a piddock protruding from a hole. (Taken on another occasion).

I often see rafts of blue-grey Anurida maritima springtails floating on the surface tension of pools in the summer, but these were smaller still and so pale they looked almost transparent. They are clearly visible in the video but I could only take very blurred still photos.

The fabulous Essential Guide to Rock Pooling by Steve Trewhella and Julie Hatcher was my first port of call in trying to identify them. The book has great photos and plenty of clear information on what to look for. Steve kindly identified these springtails as Axelsonia littorlis – a new species to me. It’s amazing what you find when you stop to look.

The best shots I could get were of a larger bug called Aepophilus bonnairei, a beetle-like creature with red eyes and a spiky coat of hairs around its back and legs. These hairs trap air bubbles, which help the insect to breathe when it is submerged.

Aeopophilus bonnairei bug on a rock
Aepophilus bonnairei bug on a rock
A juvenile Aepophilus bonnarirei.

Time was short as the tide was already turning and the waves were pounding in. I tried to photograph as many species as I could so that I could put records together afterwards. Some, like the painted top shells and the various crabs, are easy to identify.

This image has an empty alt attribute; its file name is between-plaidy-and-millendreath-january-2020-painted-topshell.jpg
Painted top shell.

One of the most striking sponges I see on the shore is the vivid blue Terpios gelatinosus. Many other sponges are harder to identify confidently.

Blue sponge - Terpios gelatinosus with keel worm
Blue sponge – Terpios gelatinosus – with keel worm

It seemed that no part of this valuable habitat was left unoccupied. To avoid any of these creatures coming to harm, we gently manoeuvred the rock back in place well before the surging waves reached us.

Different coloured patches of star ascidian among spirorbid worms, keel worms and other life on the boulder.

As always, I was left in utter awe of the fragile little creatures we saw.

It is remarkable that these animals will cling onto life here no matter how much the wind howls and the sea roars around them, while we head home to bring the plant pots in out of the wind, check the fences and put the kettle on.

Broad-clawed porcelain crab
A grey and windy day on the shore. It’s incredible that anything can survive in these pools, especially insects.

The Legendary Slug Formerly Known as Discodoris

The tide has turned and I am reluctantly preparing to leave one of best rock pooling beaches in Cornwall after a fabulous few hours in perfect conditions in the company of great friends. As you’d expect, the day has been full of interesting finds, from sponge-covered spider crabs to golden clutches of clingfish eggs. My camera batteries are running low and my hair is dripping with seawater from all the time I’ve spent poking my head under seaweed-festooned overhangs. The kids migrated up the beach a while back to investigate the picnic bag but us adults can’t bear to leave the pools. As the water creeps up my wellies, I gently turn one last rock, and then another for luck.

This small species of spider crab (Inachus sp.) was so completely covered in sponges that I couldn't see her shell at all.
This small species of spider crab (Inachus sp.) was so completely covered in sponges that I couldn’t see her shell at all.

I let out gasp so loud that it would make most people think I’d just broken a bone, but my friend knows better. She moves closer to ask what I’ve discovered, but I’m so overwhelmed with excitement that I can only babble about having, “finally found one”.

I point a trembling finger at the rock. “It’s a Disco…a Discodoris planata,” I stutter, before launching into a garbled explanation of how it used to be a Discodoris has been renamed Geitodoris, but I use Discodoris because I love that name and…

I take a few photos of the cause of my breathless wonder, straighten up and fling my arms over my head and shout at the top of my lungs to attract the children’s attention. It takes me a minute to realise that the distant child I have in my sights is not mine, but  Junior has noticed my flailing and comes scrambling across the rocks with his friends.

We crowd in the fast-filling pool and peer down at my rock. Even Junior is a bit confused by my excitement over the small, brown lump I’m indicating.

Not just a brown lump... Geitodoris planata (the slug formerly known as Discodoris planata)
Not just a brown lump… Geitodoris planata (the slug formerly known as Discodoris planata)

“It’s Discodoris,” I explain, breathlessly. Instantly, he joins my paroxysms of delight, shrieking out the great news to his friends and going through the same Geitodoris speech as me, for this unassuming slug has become something of a legend in our household.

This isn’t the first time I’ve ever seen one, but it’s the first time I’ve had a working camera with me and it’s the first “Discodoris” that Junior has seen. He is especially impressed with the white star patches on the slug’s back. These are glands which secrete a powerful acid, ideal for seeing off predators.

The white patches are powerful acid glands.
The white patches are powerful acid glands.

On close inspection, there’s a pale-yellow blob alongside our “Discodoris” (Geitodoris planata): another slug. At first, I assume from its colour that it must be a Jorunna tomentosa, a slug I often see on this shore. Indeed, there is another Jorunna tomentosa on the same rock. However, this one seems to be getting very cosy with Discodoris. In fact, it looks to me as though they are mating. The yellow slug also has a far flatter profile than any Jorunna tomentosa I’ve seen before.

Our brown Geitodoris planata and its much paler yellow mate getting friendly in the Cornish rock pools!
Our brown Geitodoris planata and its much paler yellow mate getting friendly in the Cornish rock pools!

If the tide wasn’t coming in, and if I wasn’t called away by someone further up the beach finding a giant goby, I might have been able to check the slug’s underside. If I’d done that I could have seen without doubt that this was a second “Discodoris”, a two-for-one package. The underside of Geitodoris planata is fringed in brown spots, unlike the very similar sea lemon, which is all one colour.

The fish found by some holidaymakers was indeed a giant goby. These fish are a protected species so must not be caught or disturbed without a licence. We left it hiding in its surprisingly small pool.
The fish found by some holidaymakers was indeed a giant goby. These fish are a protected species so must not be caught or disturbed without a licence. We left it hiding in its surprisingly small pool.

Fortunately, social media now enables geeks like me to swap photos with other slug-loving types and sure enough, Geitodoris planata, though usually brown with distinct white acid glands, can sometimes be pale.

Although I will record the slug as Geitodoris planata and there are important scientific reasons for the name change, this little animal will always conjure up glitter balls and platform shoes in my mind. To take photos of the fabled Discodoris, and a mating pair at that, has to be the perfect end to a perfect day.

Geitodoris planata pair
Geitodoris planata pair

Shining like pure gold - the eggs of the Cornish clingfish (Lepadogaster purpurea).
Shining like pure gold – the eggs of the Cornish clingfish (Lepadogaster purpurea).

Jorunna tomentosa slug
Jorunna tomentosa slug

One pool on the mid-shore was home to scores of colourful St Piran's hermit crabs.
One pool on the mid-shore was home to scores of colourful St Piran’s hermit crabs.

Another species of hermit crab - the tiny Anapagurus hyndmanni
Another species of hermit crab – the tiny Anapagurus hyndmanni

Sarah's common eel - our last find of the day before my wellies overtopped!
Sarah’s common eel – our last find of the day before my wellies overtopped!

“The slug formerly known as Discodoris” and a host of other rock pool creatures feature in my book Rock Pool: Extraordinary Encounters Between the Tides. Out now online and in book shops nationwide from September Publishing. If only I’d found one in time to include a photo in the book…

From Cornwall to Cornouailles – a dabble in the Breton rock pools

Once the busy summer season of rock pooling events is over, we like to jump on the ferry and get away for a few weeks. We have friends to visit and lots to do, but somehow we always end up on the beach. It’s fascinating to discover the difference it makes to be a few hundred kilometres further south.

Although there are plenty of familiar species here, there are some that are around their northern limit here in Brittany, but might put in appearance in Cornwall one day, especially as the seas warm up.

On a sheltered shore in the lee of the Quiberon peninsula, the beach where our friend Mylene spent her childhood holidays, I find a Pachygrapsus marmoratus crab, a species I saw nearby last year when I didn’t have my camera.

Pachygrapsus marmoratus crab
Pachygrapsus marmoratus crab

The rippled pattern on its carapace and the wide flat edge between its eyes make it unlike any of our native crabs. Originally found further south on the Atlantic coast, it has been working its way northwards in recent years and seems to be firmly established in Brittany now.

The three teeth along each side of the carapace distinguish this species from other rock crabs
The three teeth along each side of the carapace distinguish this species from other rock crabs

Something I didn’t notice last year is how fabulously green its knee joints are, matching its emerald eyes. It’s not afraid to use those leg-joints, scuttling away at high speed at every opportunity to hide among the dense aggregations of the invasive Pacific oyster. I nearly lose it several times before it decides to settle in the corner of a pool, allowing me photograph those hairy legs and green knees.

The fabulous green knees of Pachygrapsus marmoratus!
The wonderful green knees of Pachygrapsus marmoratus!

Junior calls out that he’s found a slug. He thinks. He’s not sure. There are so many living blobs on the shore that it can be hard to tell.

The blob is a plump yellow thing, perhaps four or five centimetres long and from the speed it’s crawling across the rock, it is most definitely a slug. Initially, I assume it’s a sea lemon, but it doesn’t quite look right. It has a more squidgy, unicoloured look and instead of the citrussy bumps of the sea lemon’s skin, this slug has rounded protrusions of varying sizes all over its back. I can’t place it so we call it a ‘Doris might be a sea lemon, species’ and I take plenty of photos to help identify it for sure later.

Doris verrucosa - the 'warty Doris' - exploring a bed of Pacific oysters
Doris verrucosa – the ‘warty Doris’ – exploring a bed of Pacific oysters

It’s over a month after we return from holiday that I remember the photos and transfer them to my computer. On screen it’s obvious that this Doris slug looks nothing like any sea lemon I’ve ever seen. With the help of some extremely geeky books, websites and a forum of fellow nudibranch aficionados, I manage to confirm that it is a Doris verrucosa. The “warty Doris”… not the most charming name, but Junior is rightly thrilled that he found it. This isn’t a species we’ve ever seen in the UK.

Each rhinophore on the slug's head is framed by two pairs of prominent protrusions and the gills are framed by a crown of tall protrusions.
Each rhinophore on the slug’s head is framed by two pairs of prominent protrusions and the gills are framed by a crown of tall protrusions.

We revisit a beach that is the polar opposite of the sheltered shore of Quiberon. Ste Anne de Palud is a west-facing windswept expanse of muddy sand framed by a north-facing rocky headland and pools, which provide an incredible habitat for all sorts of clam shells and colourful anemones as well as a perfect set of conditions for the honeycomb reef worm, which builds its huge beehive-like structures all around the rocks.

A honeycomb worm reef overhanging a pool at Ste Anne la Palud, Brittany
A honeycomb worm reef overhanging a pool at Ste Anne la Palud, Brittany

The anemones are fabulous, but so well tucked under steep overhangs of rock or so well buried in sediment that they are tricky to see, let alone identify.

Sagartia elegans anemone, Ste Anne la Palud
Sagartia elegans anemone, Ste Anne la Palud

Strawberry amemone showing its blue beadlet fighting tentacles
Strawberry amemone showing its blue beadlet fighting tentacles

Another colour variation of Sagartia elegans
Another colour variation of Sagartia elegans

Junior is digging holes in the sand and discovers just how packed with life the sand is as he uncovers dozens of thin tellin shells, which burrow their way back down as he watches. The tideline is strewn with evidence of the diversity of life beneath our feet, with spiny cockles, sea potato urchins, the delicate tubes of the worm Pectinaria belgica and necklace shells.

Spiny cockles and their relatives are common here
Spiny cockles and their relatives are common here

Pectinaria belgica worm tube
Pectinaria belgica worm tube

Necklace shell. Euspina catena
Necklace shell. Euspina catena

There’s a good chance that some of the less familiar animals we’ve seen will show up on the Cornish coast at some point. The St Piran’s hermit crab has already successfully made the crossing and I saw them first here.

A trip to Brittany feels like the perfect way to familiarise myself with creatures that I might need to identify in future. It’s also a good excuse to eat lots of pancakes and put my feet up. Both make me happy!

The vast, rich sands of Ste Anne la Palud
The vast, rich sands of Ste Anne la Palud

A juvenile sea hare
A juvenile sea hare

Slugs, snails and sunshine on my mollusc recording course

You never know what you’ll find on a beach and it’s rarely what you’re looking for. It felt like something of a fluke when an octopus put in an appearance on my mollusc course in Devon last month. I could only hope that some interesting snails and perhaps a slug or two would turn up for this week’s molluscs workshop in Falmouth for the Environmental Records Centre for Cornwall and the Isles of Scilly (ERCCIS).

The sun shone, which is always a good start, and I couldn’t have asked for a more enthusiastic group. After the morning’s presentation and a lot of work on topshell identification, we enjoyed a perfect picnic on Gyllingvase beach, taking care to protect our sandwiches from the herring gulls, before setting out to explore the rocks.

I was showing some of the group the different topshells, winkles and other shells found near the top of the shore, when someone found a coil of eggs under a stone. It was a perfect start – the eggs of a great grey sea slug (Aeolidia filomenae). We looked all around the area and couldn’t see the slug that had laid them, but it was probably still close by.

Great grey sea slug eggs - from another day because I didn't take a photo of ones we saw at Falmouth.
Great grey sea slug eggs – from another day because I didn’t take a photo of ones we saw at Falmouth.

Inspired by our early success, we carried on down the shore and one of the group found some codium seaweed. Remembering that I’d mentioned that the photosynthesising sea slug, Elysia viridis, is often found on this seaweed, she called me over.

The lump on the codium she’d hoped might be a slug was seaweed, but we examined the codium some more and soon found two photosynthesising slugs on it. The shout of, ‘Slug’, went up so that everyone could gather to take a look.

Elysia viridis, the photosynthesising sea slug. This slug retains the chloroplasts from the seaweeds it eats and they carry on producing energy inside its body.
Elysia viridis, the photosynthesising sea slug. This slug retains the chloroplasts from the seaweeds it eats and they carry on producing energy inside its body.

Gyllingvase has all sorts of seaweeds, lots of pools and steep rocky overhangs, which makes it a perfect habitat for snails. We found the egg capsules of the netted dog whelk and the European sting winkle among many other things.

‘Slug!’ The shout went up again, this time for a big brown sea hare (Aplysia punctata) and before long we’d seen several of them. They love the sea lettuce and other seaweeds that are growing rapidly in the pools this time of year. They were congregating all over the beach to lay their pink spaghetti egg strings on the seaweed.

Sea hare, Aplysia punctata
Sea hare, Aplysia punctata

We had another shout, that turned out to be this beautiful candy-striped flatworm. It’s not a mollusc of course, but was still a great find.

Candy-striped flatworm at Gyllingvase, Falmouth
Candy-striped flatworm at Gyllingvase, Falmouth

It was clear there were plenty of creatures to be found and the entire group took the search seriously, crawling on the rocks, staring into pools, lifting seaweed and bringing all sorts of finds to me.

In a kelp-strewn gully at the edge of the sea, we found more snail eggs of various sorts and some live sting winkles. A sea lemon was sheltering in a small hole in the rock, our fourth sea slug species of the day.

The sea lemon, showing its feathery gills (top) and the rhinophores on its head (bottom).
The sea lemon, showing its feathery gills (top) and the rhinophores on its head (bottom).

We put it in a pot of water to watch its rhinophores emerge from its head and its gill feathers unfurl on its back.

By now the tide was starting to turn, so I placed the sea lemon back on its rock and hurried to take a look down another promising gully. There were some anemones about, the favourite food of the great grey sea slug whose eggs we’d seen at the beginning, so I hoped I might find one hanging about there somewhere.

After a few minutes of examining an overhang and taking a look under stones I’d drawn a blank and stopped to take a look at some finds people had brought to me. I was about to haul myself back up the rocks when I spotted a long stone that was half-wedged against the rounded overhang at the back of the pool. It looked like a sluggy sort of stone, one that wouldn’t move easily and might have all sorts of sponges, squirts and other things slugs like to eat growing on or near it.

As soon as I turned the stone, I could see the colourful cerrata of a little slug. It most definitely wasn’t a great grey sea slug with its bright reds and blues. I screamed, ‘Slug!’ loudly enough for most of Falmouth to hear and fumbled with a petri dish, scared I might drop the slug in the water and lose it.

Facelina auriculata sea slug
Facelina auriculata sea slug

The great thing about teaching a workshop is that everyone there is just as excited by marine creatures as me, and this one, a Facelina auriculata, is one of the most beautiful slugs I’ve seen on the shore. It caused a lot of excitement and photo taking.

Facelina auriculata sea slug
Facelina auriculata sea slug

After returning the Facelina auriculata, which we nicknamed ‘the patriotic slug’ due to its red, white and blue colours, I turned my attention to a deep pool to look at some rainbow wrack. Lovely though the turquoise iridescence of rainbow wrack is, it wasn’t the seaweed itself that interested me, but the colony of various hydroids growing on it. These colonial animals are relatives of the jellyfish and anemones and are a favourite food of many sea slugs.

I was hoping to find a Eubranchus farrani, a colourful slug with fat cerrata and orange markings on its body, which loves to eat hydroids. I soon spotted a tiny slug, but it was something different. It was so small I could barely see it, but in the petri dish when it came out fully I could see under my camera’s magnification that it was a Polycera quadrilineata, a pretty white slug with yellow markings and yellow-tipped tentacles.

Polycera quadrilineata sea slug at Gyllingvase, Falmouth
Polycera quadrilineata sea slug at Gyllingvase, Falmouth

It was hard to see much with the naked eye, but we all had hand lenses and cameras to get a close look.

Polycera quadrilineata sea slug, Gyllingvase, Falmouth
Polycera quadrilineata sea slug, Gyllingvase, Falmouth

By this time the tide was rushing in. A last foray along a higher gully produced a cowrie shell and a perfectly orange common starfish, which isn’t a mollusc but made us happy nonetheless.

By the end of the day we’d seen five species of sea slug, the egg spiral of the great grey sea slug and all sorts of snails.  It was the kind of fantastic result that comes from lots of dedicated people searching and a good dose of luck.

I can only hope that my run of workshop luck holds for my jellyfish course later in the year. Who knows what might turn up?

Taking photos of a sea slug at Gyllingvase
Taking photos of a sea slug at Gyllingvase

A Surprise Sea Slug

Even my family look at me strangely when I suggest rock pooling in this weather. The Met Office reckons it’s going to turn out fine, but the wind is flinging water straight into our faces and the beach is deserted. We huddle down on some damp rocks and rush to eat our pasties before the rain turns the pastry soggy.

“I wonder if people realise what you go through to put pretty pictures on your blog?” Other Half says.

I nod, watching the waves crashing onto the shore and thinking that it’s worse than that. In these conditions I’m unlikely to find much, let alone manage pretty pictures.

Fortunately, I’m wrong.

Cornish Rock Pools in Looe - fuelled by rain-soaked pasties
Cornish Rock Pools in Looe – fuelled by rain-soaked pasties

After a quarter of an hour of staring into holes in the rock, taking lots of rain-blurred photos and a few passable ones of common crab and barnacles species, I’ve established that my waterproofs are anything but waterproof. If it’s possible, the rain is getting heavier.

Volcano barnacle
Volcano barnacle

Cornish Rock Pools Junior and his dad have wandered off and are probably reaching their tolerance limit. I find a stalked jellyfish and think that’s likely to be the most exciting find of the day.

A stalked jellyfish (Calvadosia cruxmelitensis) in a pool
A stalked jellyfish (Calvadosia cruxmelitensis) in a pool

I lift the edge of one last stone. There are some thick yellow sponges and the rock is crusted over with bryozoans. Broad-clawed porcelain crabs are scuttling along and there are little banded chink shells. On the far side is a spot, maybe half a centimetre across. It’s hard to make it out, but it has a blue-ish tinge and a lined appearance, like an anemone out of the water.

I think it’s a sea slug, but it’s far too delicate to pick off the rock and even if I do there’s nowhere to put it. I need to see it in water otherwise it’s just a blob of jelly. There’s no chance of that here at the base of the gully where the waves are pounding in, so I heave the boulder up the shore and lower the side with the slug into the nearest pool.

Facelina auriculata sea slug unfurls its tentacles and cerrata in the water.
Facelina auriculata sea slug unfurls its tentacles and cerata in the water.

Shelter’s hard to come by. The surface of the pool distorts with every gust of wind and the rain goes up the back of my coat and into my ears as I lean over to hold the rock in position. Straight away, I know this is definitely a sea slug. In the water, its cerata pop up all over its back and long tentacles and rhinophores unfurl around its head.

This is the sort of colourful, beautiful slug that I’m always hoping to find and only rarely do. Under the camera it has striking red lines and markings up its cerata, white stripes down its head and an iridescent blue sheen that changes as it moves.

Facelina auriculata - the red patch behind its head is the oesophagus
Facelina auriculata – the red patch behind its head is the oesophagus

This is a new slug to me and I can’t wait to look it up when I get home to check the exact species. In the meantime, I take as many photos as I can before hauling the rock back to the same spot where I found it. That done, I rush up the beach to tell my Other Half, Cornish Rock Pools Junior and everyone else I see that day about how amazing my sea slug was.

Facelina auriculata sea slug - from different angles the colours seem to change.
Facelina auriculata sea slug – from different angles the colours seem to change.

Thanks to my pile of identification books and the quick responses of the hugely knowledgeable members of the NE Atlantic Nudibranchs forum on Facebook, I soon have it confirmed as Facelina auriculata (previously known as Facelina coronata).

This slug is found around many coasts of the UK, and is meant to feed on hydroids, although I didn’t see many in the vicinity of this one. I’m very lucky to find it intertidally on such an average tide.

If you think rock pooling isn’t a normal sort of thing to do in January, I can understand that. You’re probably right and I think my family would agree with you, but you never know what’s going to turn up next in the Cornish Rock Pools.

Sometimes it’s worth braving the horizontal rain just in case.

See - it's lovely out there! Looe rock pooling in January.
See – it’s lovely out there! Looe rock pooling in January.

A Xantho pilipes crab - they vary in colour but always have hairy back legs.
A Xantho pilipes crab – they vary in colour but always have hairy back legs.

And did I mention I found a sea slug? So excited...
And did I mention I found a sea slug? So excited…

Winter Solstice Rock Pooling

It’s the shortest day of the year, but there’s no shortage of colour and life in the rock pools here in Looe.

I try out a pool I’ve not explored before and am blown away by the variety of animals going about their day, searching for food and shelter.

Easily my favourite find of the day is this European three-spot cowrie. Although they’re not uncommon here on the south-east coast of Cornwall, at low tide they’re usually retracted in their shells  or abseiling from the rocks on a mucous thread.

To find one fully extended out of its shell, its orange syphon probing the weeds and its leopard-print mantle curled around its shell, is fabulous. I’ve always loved finding these shells washed up on the beach, but the live animal is incredibly colourful. It looks far too tropical for our cold waters.

European three-spot cowrie looking glamorous
European three-spot cowrie looking glamorous

European three-spot cowrie
European three-spot cowrie

It’s not a great low tide but this large, shallow pool is ideal for all sorts of creatures.

Painted top shells are plentiful in this pool - there must be lots of food for them.
Painted top shells are plentiful in this pool – there must be lots of food for them.

Like the cowrie, this thick-lipped dog whelk has a long syphon.
Like the cowrie, this thick-lipped dog whelk has a long syphon.

A Velvet swimming crab lurking under an overhang
A Velvet swimming crab lurking under an overhang

These hydroids and bryozoans have their feeding tentacles out
These hydroids and bryozoans have their feeding tentacles out

A stalked jellyfish - Calvadosia cruxmelitensis
A stalked jellyfish – Calvadosia cruxmelitensis

Worm pipefish
Worm pipefish

A young snakelocks anemone
A young snakelocks anemone

Everywhere I look, there are more animals going about their business. Hermit crabs scurry past me and a fish takes shelter under my welly.

From now on, the days will get longer, and before long the sea slugs and fish will begin to move in to the shore to spawn. It seems some can’t wait for spring – even today I find a pair of Berthella plumula sea slugs under a stone!

If you’re in Cornwall this Christmas, take a look at the rock pools. You won’t be disappointed.

Nadelik Lowen!

Berthella plumula sea slug - I find two under a rock so it looks like they're planning to spawn soon.
Berthella plumula sea slug – I find two under a rock so it looks like they’re planning to spawn soon.

Who needs a Christmas tree when you can just decorate yourself in seaweed? 'Decorator' spider crab - Macropodia sp.
Who needs a Christmas tree when you can just decorate yourself in seaweed? ‘Decorator’ spider crab – Macropodia sp.