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Planet of the Nudibranchs!
Posted by Graeme Lyons , Tuesday, 29 July 2025 11:23
I've just got back from a very exciting and spontaneous two-day stay on Anglesey. It involved what it best described as an avalanche of nudibranchs! It's all down to my friend Mark Colvin (and his daughter Charlotte). I had a weekend free for the first time in years and was planning to go to Cornwall. I was feeling rather discombobulated after having my first full blown migraine in 30 years on Friday morning, when Mark sent me a text saying he had just seen 23 nudibranchs of some eight to ten species! I got up the next morning, booked a B&B and was there by 4.00 pm for the next low tide.
Directly under the Anglesey side of the Menai Bridge is somewhat of a nudibranch hotspot. Indeed, I saw at least seven species when I was there. So, put on your breathing apparatus, set phasers to stun and prepare to be beamed down to the Planet of the Nudibranchs!
First up (and this is perhaps the commonest species there - albeit I have only seen this once before on Jersey) is the widespread Facelina auriculata! The iridescent blue/purple and long, gracile nature help to distinguish it from Facelina bostoniensis.
I am pretty sure this one was Facelina bostoniensis which was also present there in numbers. I have only seen this once before at the Pound.
After the Facelina, Edmundsella pedata was the commonest, with more than 10 found under one rock grazing on hydroids (I will come back to this rock later). These are incredibly wonderful animals. Common on Jersey, I first saw this on the Isle of Wight but I have never seen it in Sussex.
I found a mature Sea Lemon Doris pseudoargus. The others put it in a container with some of the other species, so you can see here how much bigger they are!
I found one Palio nothus under a rock too, I have only seen this on the Isle of Wight before but it seems a common and widespread nudibranch.
Yet amazing as this was, I was lacking a sea slug new to me! Dopamine deficiency was kicking in. So I went back for the low tide on Monday morning before I left Wales. The tide was coming in when I stumbled on the rock with all those grazing Edmundsella under. I thought I would count them using my close-focus binoculars when I spotted a totally different colour. There, poking out of the darkness of the hydroid forest, were a dozen bright orange-red, brilliantly white-tipped flares! There were also white highlights on the tentacles and rhinophores and not a suggestion of pink on the body. The rhinophores were also lealy not annulated like Facelina. This was a lifer! BUT it was under 4 mm and hard to get to.
I did eventually get it in a tray for a closer look and I soon came to the conclusion this was Microchlamylla gracilis (thanks to the amazing field guide). My 15th species of nudibranch in the British Isles! Nearly half of all the species I have ever seen I saw at this site in one weekend. Bonkers!
Sublime! We saw over 50 individual sea slugs on Saturday night, and they had at least two species on Friday night that I did not see (one of which I have never seen). I will therefore be back.
There was some other nice things there too. Like Lightbulb Sea Squirts (still scarce in Sussex).
And lots of these hydroids, Entopleura larynx. . There are sea slugs that eat just this and it seems that the other saw one of these on Friday night! How exciting, I love to come away seeing lots of stuff but not everything as it leaves me wanting more! A massive thanks to Mark, Charlotte and all the others who came out!
Now I did a lot of other rock-pooling, snorkelling and entomology around the island in 48 hours but I will leave this for another time as it has been 15 years since I last visited the island and some 22 since I lived there, so I would like to do it justice. Now I'm off looking for rare mirids...
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