Tag Archives: nudibranch

Summer Rock Pooling At Millendreath

Irys and her mum are hoping to see a sea slug. As regular readers of this blog will know, I am more than a little slug obsessed, so we quickly hatch a plan to visit “Slug Alley”.

The day is grey and mizzly, as is typical in Cornwall any time of year. These damp conditions are ideal for sea creatures that would hide away on sunnier days to avoid drying out. The tide is nothing special, but there is still a fair chance of finding slugs if it drops enough to allow us to access the deep rocky overhang.

This flat periwinkle is happily searching for seaweeds among the damp sponges and sea squirts.

Tiny blobs of jelly aren’t easy to see, especially when the whole of the rock is coated in an assortment of blobs already. As well as some blobby seaweed, there is a rich turf of sponges, sea squirts and bryozoans, all competing for space in this damp, shaded area.

Star ascidian colonial sea squirts at Millendreath, Cornwall.

Among the hydroids I find a few super-small blobs that might be Doto sea slugs, but out of the water it is impossible to tell. Junior finds a “huge” stalked jellyfish a few centimetres long, which can only be a Calvadosia campanulata.

Calvadosia capanulata stalked jellyfish.

This jelly is common in the summer and can be a few centimetres long. The tiny turquoise spots on the outside of the bell are unique to this species.

Less obvious, but more numerous Haliclystus octoradiatus stalked jellies are everywhere at the moment.

Haliclystus octoradiatus stalked jellyfish.

I even find one under a stone. These stalked jellyfish normally only live on seaweed, so this one has probably been dislodged by something and will try to loop its way back to the seaweed when the tide comes in.

Stalked jellyfish under a stone looking rather sorry for itself!

Irys finds a blob and shows me. It is small, brown and jelly-like and I am pretty sure it is a slug. I try not to get excited until we are sure. Carefully, we remove it from the sponge and pop it in a pot of seawater. In true magic slug style, the little creature sticks itself to the bottom of the tub and begins to open up and move. This is not either of the species I first thought it might be.

Irys’s fabulous find – Aegires punctilucens, a nudibranch sea slug.

We transfer the slug to a shallow petri dish to get a better look. As soon as it is under the camera, it is obvious that this slug is indeed something different. It’s a species I have only seen before in my (many) books and it’s an absolute gem. It even looks like it is hewn out of rock with its bumpy, knobbly back, but between the bumps, the body is smooth, dark brown and decorated with spots of iridescent blue.

Aegires punctilucens sea slug at Millendreath

This is a fabulous find and I am in awe that Irys spotted it having never seen a sea slug before. I have to check the name in a book when we get home – Aegires punctilucens. Punctilucens means points of light shining through or dawning… a perfect description.

Aegires punctilucens sea slug exploring the pool at Millendreath.

We take a lot of photos  of the slug in a petri dish and in a shallow pool before returning it to the rock where we found it, where it will feed on the sponges. Ideally we would take photos of it in situ, but out of the water it really is featureless brown goo!

The tide has dropped a little more, so we explore the pools further down the beach while we can.

Among a forest (or salad garden?) of sea lettuce, I spot this beautiful Polycera sp. slug. It is fairly large for this species and has striking yellow lines.

Polycera sp. nudibranch sea slug.

It is likely Polycera quadralineata, the four-lined sea slug, but it can be difficult to distinguish from Polycera norvegica. This lovely slug likes to eat bryozoans – colonial animals that form mossy sheets on the seaweed and rock – so it can become quite numerous this time of year.

Polycera sp. sea slug at Millendreath

I hadn’t been sure of finding much today on such a small tide, but slug alley has done us proud. We are all delighted with our finds and we are already planning another expedition together next time Irys and her mum visit.

Another creature in an unusual place – Aplidium turbinatum sea squirt on sea lettuce.

If you are visiting the beach this summer, be sure to rock pool responsibly and safely. Check the tides and leave everything as you found it. Read my top tips for successful rock pooling.

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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.

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…

Warming up for the Weekend

Spring tides and slightly more spring-like weather might finally coincide this weekend, so I’m preparing for a big weekend of rock pooling. If all goes to plan, I’ll be reporting back next week. In the meantime, I’m readying my waterproofs, planning which beach I’ll go to according to the wind direction and sorting out my photos from the last month. And of course, I’ll be at the Looe Marine Conservation Group Rock Pool Ramble on Monday at Hannafore beach, so maybe I’ll see you there?

One beach I’m hoping to visit on Saturday is Millendreath. This sheltered south coast beach has an interesting geological history. Somewhere under the sand is a submerged ancient forest. Whether the nutrients come from there, drift along from the Looe river, or both, this beach has a unique fauna and is always full of surprises.

Pheasant shell at Millendreath
Pheasant shell at Millendreath

In the past I’ve found masked crabs, weever fish and unusual swimming crabs here. On my visit last week, it was all about the sea slugs and cucumbers.

In the chilly breeze it felt less than spring-like, but these things seem not to bother the rock pool creatures. Sea lemons, a type of sea slug with a big circle of feathery gills on their back and pocked citrus-like skin, were everywhere.

Sea lemons - a type of sea slug - enjoying each other's company.
Sea lemons – a type of sea slug – enjoying each other’s company.

And so was their spawn.

A spiral of sea lemon spawn at Millendreath
A spiral of sea lemon spawn at Millendreath

A species that seems to love the conditions here is the brown sea cucumber, Aslia lefevrei, which likes to hide away in holes in the rock with just its retracted tentacles sticking out. When these are fully extended they have a frilly, carrot-top appearance, but at low tide all we see is a yellow and brown blob.

Brown sea cucumber, Aslia lefevrei, at Millendreath
Brown sea cucumber, Aslia lefevrei, at Millendreath

The tip of a brown sea cucumber, Aslia lefevrei
The tip of a brown sea cucumber, Aslia lefevrei

Among the seaweed at the edge of the shore, I spotted a fleck of orange. Old seaweeds often turn bright colours as they die back, but this fleck wasn’t attached to anything. After fumbling about in the cold water for as long as I could bear, I managed to scoop the fleck up and tip it into a petri dish.

Much of my time on the shore is spent staring at things, wondering if they’re animals or just tricks of the imagination. Often they’re nothing, but this one was definitely a something.

My blob - a Eubranchus farrani sea slug with 20p for scale
My blob – a Eubranchus farrani sea slug with 20p for scale

As it settled in the water, the blob began to unfurl and then to secure itself to the dish. It was definitely a sea slug, although still quite hard to see as you can tell from its size compared to the 20p piece.

Eubranchus farrani sea slug - close-up
Eubranchus farrani sea slug – close-up

The chunky cerrata on its back and the orange on its body were typical of the species, a Eubranchus farrani. By far the smallest one I’ve ever seen.

Conditions were too cold to spend any longer with my hands in the water, so I retreated to the upper shore to look for anemones with Junior and to let him dig around the stream. Perhaps one day he’ll dig down to the submerged forest?

Beadlet anemone in a pool near the top of the shore, Millendreath
Beadlet anemone in a pool near the top of the shore, Millendreath

Even on uninviting, cold days, there are always things to find. Millendreath never fails to surprise me. Who knows what will turn up this weekend? Conditions should be easier, but I’m taking no chances. Other half got a big thermos flask for his birthday and I’ll be filling it with hot chocolate before we go out!

Xantho hydrophilus crab
Xantho hydrophilus crab