Dotty Doto Sea Slugs (and an ode to a spade)

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!

Other finds…

Common periwinkle
Cowrie
Stalked jellyfish (Haliclystus octoradiatus)
Spider crab (Macropodia sp.)

Staycation Safari

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!

If you would like to find out more about rock pool wildlife or go on your own rock pooling adventures, be sure to pick up my books Rock Pool and Beach Explorer. Out now with September Publishing and available from all book shops and online.

May Half-Term Rock Pooling

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.

Make every beach trip an adventure with my children’s book, Beach Explorer: 50 Things to See and Discover. It’s packed with hands-on activities, facts and quizzes.

EVENTS

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 with Junior (photo by Other Half)
  • Green shore urchin, Hannafore, Looe
  • Passing round a spiny starfish
  • Junior getting to know our wrasse-friend
  • A juvenile turbot at Lundy Bay
  • Cornish Rock Pools junior drying off in the sunshine 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
  • Although painted topshells are a common sight on my local shores, I never tire of photographing them.
  • 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?

Find out more about rock pooling with my top tips and guides.

BEACHES

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 great smile.
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

In the water the sea lemon's rhinophores and frilly gills emerge and we can see its wonderful colours
Sea lemons a type of sea slug. They eat sponges and breathe through the frilly gills on their backs.

Green Shore Crabs

Green shore crab with eggs - Christmas eve 2018 in Looe
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 periwinkle in the Cornish rock pools
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.

Team Rock Pooling Near Falmouth

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.
Velvet swimming crab hiding in the sand.

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 annulicornis.

 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.

Chilly Spring Tides in Looe

I used to think I knew my local rocky shores well, but during this last year of lockdowns and staying local, I have been almost nowhere else. What is remarkable, though, is not the intimacy with which I now know every stone and every overhang, or even the way I like to call on some of the long-term inhabitants, but the fact that, despite the familiarity, there are still surprises on every visit.

Photo by Cornish Rock Pools Junior of the beach looking idyllic – looks can be deceptive: it was freezing!

With a brisk northerly wind counteracting any warmth the sun is trying to put out and a strong swell racing in, the conditions are far from ideal. Other Half and Junior start eagerly enough, discovering some light bulb sea squirts on the edge of a boulder, but even before our film maker friend, Greg, joins us, Junior has taken to sitting at the edge of the pool we are exploring in a largely futile attempt to hide from the wind.

Light bulb sea squirts on a rock covered in bryozoans and spirorbis worms.

“You have to look at this,” Junior calls, holding up a large stone he has found. “I think there are piddocks in it.”

Piddock holes in Junior’s stone.

We peer into the deep, rounded holes in the stone. In one we can see something retreating into the darkness. There are certainly piddocks in there. These odd bivalve molluscs drill into soft rock, boring out deep holes in which they hide, safe from predators.

Weirdly, piddocks are known to have bioluminescence, glowing blue-green in certain circumstances. The rock also looks as though it has been nibbled at by juvenile piddocks or another rock-boring animal. Air-breathing mites have taken up residence in the holes and bristly chitons cling on to the surface.

Bristly chiton on Junior’s piddock rock

Greg arrives to set up, but we’re already feeling the cold and the water is wind-blown and silty from the rough seas. It’s looking far from ideal for capturing the footage of Looe’s amazing marine wildlife that we were hoping for.

Despite our numb fingers we crack on, looking for St Piran’s hermit crabs and fish eggs to film.

We find both, but the crabs are huddled together and hiding in their shells, while the rock goby eggs we find are freshly laid, so aren’t developed yet. In another week or two, hundreds of eyes will gaze out at us, but not today.

Freshly laid goby eggs on the rock

While I can still move my frozen fingers a little, I take photos of a young adult sea hare. It is already many times the size of the juveniles I saw here earlier in the year, and is still putting on weight as it  chomps through the copious supplies of fresh, new-growth seaweeds.

Sea hare (Aplysia punctata)

This sea hare still has some filling out to do, but as though it is keen to prove that it’s already a grown-up, it has laid a tiny patch of its tangled pink spaghetti spawn on the rock.

Sea hare eggs – their spawn looks like pink spaghetti and feels hard to the touch.

The gangly legs of a sea spider catch my eye, flailing about in the seaweed. Ungainly and fragile, it emerges and sways past. A clutch of orange eggs held under its abdomen.

Nymphon sp. sea spider.
The orange mass under the sea spider’s abdomen is the clutch of eggs.

By now the enjoyment we are getting from encountering creatures is fully counterbalanced by the discomfort of being freezing. I am getting the shivers and it is painful to hold my camera in the icy water, but these big spring tides only come a few times a year so we have to try to make the most.

Heading for the lower shore while we can, we slip and slide on the seaweed that covers every rock. We find a pair of small clingfish but they slip away into the weed before Greg can get in position, performing graceful dives off the rock, heads up, backs arched, like parachutists in freefall. They are so well camouflaged in the pool that we stand no chance of finding them again.

I only see this little clingfish for a few seconds before it dives off the rock.

In the nearby pools I find green shore urchins, chitons and hydroids. This area is rarely out of the water, so is rich and stable with a diverse array of marine life. Some of the nearby rocks are often targeted by people equipped with spikes foraging mainly for crustaceans. The foragers often leave a trail of destruction: stones and seaweed are tossed aside as they go, their metal tools scrape and damage the soft-bodied animals that live on the rocks and if they find any large animals, they take them home to eat.

Green shore urchin with tube feet extended. Animals like these are easily damaged or lose their safe hideaways if poeple move their rocks.

Like other conservationists, I put a lot of energy into studying the ecology of my local patch and into teaching others to love and care for our wildlife. It breaks my heart to see others entering the environment only to destroy it with little regard to sustainability. With the rise of videos promoting taking wild animals from the shore, I find myself having to be increasingly careful not to share any images of commercial species in case it leads to them being targeted. Foraging may have a lower impact on the marine environment than trawling and industrial fishing and has always happened to some degree, but the number of foragers is growing and the impact is not negligible.

There are many soft-bodied animals on the shore, like this daisy anemone with its beautiful purple mouth.

Although people are only officially allowed to remove certain species of crustaceans above a minimum size, this is not enforced by anyone and it seems there are no controls on foraging for ‘personal consumption’, even in a Marine Conservation Zone. These sheltered intertidal pools are an important nursery for young crabs, so minimising disturbance here is important to maintain stocks, as well as for the rest of the ecosystem.

Today I’m relieved to see no sign of foragers. The uncomfortably cold weather is keeping people away, keeping the animals safe. The thought warms me a little.

This ‘White-ruffed’ Aeolidiella alderi sea slug had recently eaten a daisy anemone and taken on the anemone’s colours.

Back to the pools and I am excited to find a slender purple whelk on a tuft of red seaweed. This elegant Raphitoma purpurea is the first live one I’ve found on this stretch of rocks. The shell is striking with its criss-cross of sculptured lines and deep red-purple colour, marked here and there with splashes of white.

Raphitoma purpurea – a purple whelk.

The snail has fully extended with its purple-spotted proboscis and is exploring the pool, its dark eyes contrasting starkly with its pearly white body. I spend as long as I can quietly watching it gliding along, feeling its way.

Purple whelk, Raphitoma purpurea, exploring the pool with its fabulous proboscis.

Despite the cold, the wind and the shivers, the day is far from wasted and this is just the start of a week of super-low tides. Once again, the beach has offered up something new.

Photo by Cornish Rock Pools Junior – me near my purple whelk. Proudly unglamorous as always!

If you are visiting the Cornish Rock Pools, find out how to discover lots of amazing creatures safely and sustainably with my beginner’s guide.

A Shore In Recovery on St Piran’s Day

We tread extra-carefully around the pool, even though we’ve already guessed the St Piran’s hermit crabs won’t be here. The trail of destruction left by the powerful easterly gales is evident: boulders have been lifted by the waves and tossed far from their usual positions, the rich coatings of sponges, squirts and hydroids on their undersides gone. Life is still going on but not as before.

Junior finds a rock goby and some pipefish, but the pool feels like a shadow of its former self. The signs are not good for the nursery of young St Piran’s hermit crabs* (Clibanarius erythropus) that we have been monitoring for the last year.

One thing we have learned from watching these starry eyed, red-whiskered, bristly-legged hermit crabs is that they tend to huddle together. Unlike our common ‘Bernard’ hermits, we usually find the St Piran’s crabs congregated in just two pools on the beach. In this particular pool, there is a central rocky island where all the tiny young crabs like to hang out under a sponge-coated rock, scuttling around like a bunch of kids at the soft play, while the adults are normally found quietly feeding in an adjacent pool.

The St Piran’s hermit crab nursery last year. Every shell has a juvenile St Piran’s crab in it.

We haven’t seen a single St Piran’s hermit crab in the adult pool. They are easily distinguished from the common hermit by their equal-sized claws and bright red antennae, which are visible at a quick glance, even if most of the crab is well-hidden in the shell.

A fully grown St Piran’s crab with the distinctive red antennae, equal sized claws, black and white-spotted eyes and blue-striped leg tips.

As we approach the nursery area I almost don’t want to look. I see a common periwinkle shell sprout legs and my heart jumps. I kneel on a rock to look closely, but it is a common hermit crab, using its oversized right pincer to explore the coral weed, searching for food.

The common ‘Bernard’ hermit crab has yellow-green eyes, a right claw that is bigger than the left and pale antennae.

Among the nursery rocks, there is nothing.

Last time we were here, before the storms hit, every little shell had a St Piran’s hermit crab inside. Now, apart from a broad clawed porcelain crab clinging to the underside of a stone, the area is eerily quiet.

Cornwall’s shores are no strangers to fierce weather and, in places, there are signs of a recovery already, with new seaweed growth and newly-forming sea squirts. St Piran’s hermit crabs, on the other hand, are already at the northern limit of their range here, so they may not cope well with cold winter gales and dips in the sea temperature.

At the far end of the pool I find a chiton on the rock and stop to take a photo. These animals are molluscs but look more like woodlice than snails with their plate-armour shells. Unlike their crustacean look-alikes they have no legs and live firmly attached to the rock.

The colours of the chiton (Lepidochitona cinerea) blend in with the rock.

A flat periwinkle shell on the sand behind the chiton catches my eye. It’s not an unusual shell, but the living shells are usually found feeding on the seaweed and most of the loose shells have been swept away by the storm. There are other small shells close by and they are likely to all be hermit crabs.

My instincts are good. Just as I turn the flat periwinkle shell and glimpse the red antennae deep inside, Junior crouches next to me and shouts that he thinks he can see a St Piran’s crab.

Our first glimpse of a your St Piran’s hermit crab in the pool.

We soon discover that every little shell in this part of the pool is a St Piran’s. Our nursery crabs are still here and have upgraded to bigger shells. There are dozens of them.

Our St Piran’s crab emerges to check us out. It still has some growing to do but is far bigger than last year. It now has the classic colours of the adult crab.
We soon discover lots more shells, all with St Piran’s hermit crabs inside.

It is still early days for this hermit crab that returned to Cornwall’s shores relatively recently after a long absence. In the past it was only an intermittent resident but warming seas may enable these hermit crabs to breed successfully here. On the other hand, an increase in storm events or a weakening of the Gulf Stream could have the opposite effect. A changing climate risks heavier rain bringing more pollution from our rivers and changes in marine oxygen levels and in the plankton on which the food chain depends.

The marine ecosystem is sensitive to our changing climate and so complex that it is extremely hard to predict the exact impacts of changes. (If you’re interested to find out more, check out the Marine Climate Change Impacts Partnership 2020 Report Card).

Further down the shore we find slightly less storm damage and some of the rock pool residents in their usual places. A young topknot flatfish demonstrates its ability to sucker onto the rocks and glide across the seabed, moulding its body to every contour.

Topknot flatfish suckering onto the rock.

In what feels like a reward for our persistence, we find a fabulous Geitodoris planata slug on the lower shore. This time of year, lots of slugs are beginning to spawn.

Geitodoris planata (formerly known by the wonderful name Discodoris planata). The white patches on its back are acid glands used as a defence against predators.

We find a second G. planata in another pool. I am tempted to do some matchmaking, but we leave the slugs where we found them and let nature take its course.

The second Geitodoris planata, looking especially flat and starry.
A close-up of those acid glands (the white stars).

The sun is shining, the St Piran’s crabs are still here, we have seen our favourite nudibranch slug and we have every reason to think that the shore will recover well from the impact of the storms as the spring arrives.

All that is left to do is to head home to prepare our pasties and saffron buns for St Piran’s Day. I would share photos of them, but they were gone too fast!

Gool Peran Lowen!

* I understand that some our lovely neighbours in Devon aren’t so keen on the use of the common name ‘St Piran’s’ for the Clibanarius erythropus hermit crab, which has returned to parts of West Devon as well as to Cornwall. I am completely biased, but the name seems a good fit and it saves me from attempting to pronounce the scientific name. The legend of St Piran says that he was thrown into the sea in his native Ireland with a millstone tied to him, but floated across the sea to Cornwall. The hermit crabs also arrived floating in the plankton from somewhere, most likely Brittany, which also has connections with St Piran. The hermit crab’s striking black and white eyes match the colours of the Cornish flag. I’ve heard plenty of other common names for this crab and anyone can invent their own. In other parts of Europe Clibanarius erythropus has names meaning ‘Little Hermit Crab’, ‘Devil’s Hand Crab’ and ‘Antisocial Crab’, among others.

A Year of Cornish Marine Life

Like everything else about 2020, this is a strange New Year’s Eve. Many have lost loved ones this year, and most of us have spent the festive season apart from friends and family. Whatever the year ahead brings, it will be made better by connecting with the natural world and doing the small (or large) things that we can to build a better society and environment.

On the eve of 2021, I am struggling personally to come to terms with losing EU citizenship and all of the opportunity, discovery and connections it has brought me. International cooperation is essential to tackling the global issues that face our wildlife and we will have to work harder than ever to build understanding and find solutions to problems that cannot wait.

Life will go on and I am super-excited about my new children’s book, Beach Explorer, due to be published in the spring. As ever, I will continue to bring you the very best of the Cornish rock pools straight to your computer through my blog.

To bring a little cheer to myself and to you, here are a few of my favourite rock pool wildlife photos from my encounters this year. I hope you will be inspired to get outside and meet your own local wildlife, and to join all of us who are working to protect and restore nature.

A Happy and Healthy New Year to All! Bonne Année 2021!

A painted top shell – January 2020

Xantho pilipes crab – February 2020.
Pagurus cuanensis, the hairy hermit crab. March 2020
Bright coloured sponge (Prob Oscarella sp.) April 2020.
“Cedric the spider crab”. Photo by Cornish Rock Pools Junior. May 2020.
Juvenile masked crab moult. June 2020.
Cladonema radiatum – an athecate hydroid medusa. July 2020.
Calma glaucoides sea slug with its spawn. August 2020.
Star ascidian growing on seaweed. September 2020.
Dahlia anemone. October 2020.
Facelina auriculata – October 2020.
My first ever Xaiva biguttata crab! October 2020.

Migrating Prawns and Blue-Rayed Limpets

Junior normally keeps a low profile on this blog, but for several years now, he has been taking his own photos and videos of marine life. He recently put together this lovely video for Cornwall Wildlife Trust’s Your Shore Beach Rangers project. It showcased alongside other amazing videos by local young people last weekend at the virtual See You at the Sea Festival and he would love to share it with all our Cornish Rock Pools friends.

My favourite part of the video shows something Junior discovered in Looe a couple of months ago: a prawn migration. I was crawling around in waders with my head under a rocky overhang at the time, so I only saw the tail end of the procession as it advanced with the incoming tide. Fortunately, Junior managed to capture some fantastic footage of hundreds of prawns galloping along the seabed, all heading in the same direction in their hunt for food.

Junior’s photo of a common prawn (not migrating!).

Also featured in the video are Junior’s top photographic subjects – the blue-rayed limpet and sea slugs. He’s even coded an animation showing a day in the life of a corkwing wrasse family. We hope you enjoy his work.

Blue-rayed limpets by Cornish Rock Pools Junior

Junior’s friend, Rowen, has also created a video for the festival showing her beautiful marine artwork and how she creates it, all accompanied by incredible facts about the animals she draws and paints. She would love you to take a look.

All of the videos are available to view on the Cornwall Wildlife Trust Marine channel on YouTube. The three with the most likes and views and that catch the judges eye will win prizes this weekend!

I have been writing my new children’s book this year (due to publish spring 2021), but with that nearly ready, I’m looking forward to sharing lots of the fabulous creatures I’ve been seeing in the rock pools over the last few months. Watch this space!

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.

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