The Lyons Share

Soft power

Posted by Graeme Lyons , Sunday, 17 August 2025 14:44

Yesterday I was heading back down from Broughton Sanctuary in Yorkshire and I fancied a slight detour to Anglesey to look for some more sea slugs. It was a glorious morning when I got to Menai. Now, it wasn't a great tide (about four days after the first lowest tides of the month) but I had some excellent gen from Ian Smith on a couple of tiny saltmarsh sea slugs (not nudibranchs but sea slugs none-the-less) just to the west of Menai bridge. One being very common and one only very recently being found there. It took me about 15 minutes to get my eye in and amazingly, I found the scarcest of the two species first. Here is an Alder's Sea Slug Alderia modesta on some Vaucheria algae. Close focus binoculars are so incredibly helpful here (the individuals I saw of this and the following species were all about 2 mm). The first image is of it on the alga as I found it, the second in a tray.

And here is Limapontia depressa in the field above and below (on the left) with Alderia moedsta on the right. Aren't they cute!?

With two lifers under my belt by 9.00 am, I headed back to the nudibranch hotspot with an idea in mind. A few weeks ago, Mark Colvin sent me a photo of a species he had found there and I was convinced it was going to be Catriona auriculata. This species feeds on these rather spectacular hydroids that are common there, called Ectopleura larynx. So my plan, take my time with each rock and search the hydroids slowly and carefully. The first rock I turned had four impressive Edmundsella pedata there. This is such a gob-smakingly-beautiful creature. I then put about an hour or two in searching the various hydroids for sea slugs but especially the distinctive Ectopleura larynx (below) for Catriona.

Shortly after I got there a chap arrived who was looking for bait for catching Sea Bass. He was working annoyingly close to me, turning each rock quickly and smashing it back down (at least he was putting them back). It was quite destructive and very distracting. I was *this* close to giving him a piece of my mind when I found two more large Edmundsella pedata and called him over. I let him have a go with my close-focus bins and I watched in real time this guy realise why he needs to put the rocks back more carefully. He was blown away and really grateful, taking many photos. When I succeeded in finding Catriona aurantia he excitedly came over to me again and ended up proudly showing me his Sea Bass catches on his phone but as he went back to looking for bait, there was no smashing the rocks back anymore. As he left he thanked me for opening his eyes to these tiny creatures and I honestly believe his rock smashing days are over. It was a really cool moment, we shook hands and both our lives were enriched.

Anyways, sea slugs are like the weevils, mirids or leaf beetles of the sea! They often only eat one thing, so they really appeal to me. I have a particular affinity with phytophagous species when surveying invertebrate for work in grasslands and this interest transfers to nudibranchs - it's proper ecology. So I knew there was lots of food and searched every clump of hydroids I saw. I suddenly spotted (much smaller than I was expecting, do doubt another immature) the distinctive repeating pattern of nudibranch cerata. Can you spot them here hiding at the base of hydroid? I never would have found them without the binoculars and a plan. And being a rather persistent type.

It took a while to encourage it out, but I did! Anyways, my 16th nudibranch. Well chuffed. Here's some more shots.

I took a small clump of Ectopleura larynx back home and amazingly found two crustaceans among it I have never seen before: Apocorophium acutum and Jassa falcata. I must take more samples home!

Posted in Church Island, crustaceans, hydroids, Menai Bridge, sea slugs | 0 comments