Last week I was on holiday in Bretagne (Brittany), France. There was not a lot of opportunity for snorkelling or rock pooling activities, but the last day I checked out the pontoons of the large marina in Trinité-sur-Mer. I was not disappointed; the pontoons in Cornwall are full of life, but these ones 200 or so kilometers further south were exceptionally diverse. The most striking find was that of orange, red and purple Rosy feather stars Antedon bifida. These also occur in the UK but I had not seen these yet here so I was quite excited. I did not go into the water myself and the photos I took holding my camera under ended up being not great so I took some shots from above water as well, too bad I did not have more time!
The first photo below gives a good impression of how abundant and diverse life attached to these pontoons is. Many species are the same as the ones I see in Mylor marina, including invasive species such as the Bryozoan Bugula neritina and the tunicate Styela clavata. In addition to the many sponges, anemones, mussels, oysters and colonial tunicates I even saw things such as scallops (not sure which species) and urchins (Psammechinus). The peacock worms were absolutely huge. The plumose anemones Metridium senile looked different to the ones I am used to here to with orange individuals having brown collars which sometimes were really big and wavy. It seems no one that moors their boat in a marina ever takes notice of what is attached to the pontoons, but they should, as the diversity and beauty can almost rival coral reefs. I hope I can go back one time to properly investigate but for now I will check out the local marina’s and keep an eye out for feather stars…
Tag Archives: Metridium senile
Aquarium Update 14: anemones
A short update on the aquarium; I have collected some more anemones and hope to collect a lot more now spring has started (I went for my first dive of the year this Friday; it was really nice to be back in the water but the visibility was really bad and it was only 9 degrees!). I do not have a decent full tank shot (FTS as it is called on aquarium fora…) but decided to post some quick iPhone pics anyway. The first photo shows three species: top left is a Diadumene cincta or lineata, bottom left a Dahlia anemone Urticina felina and the two on the right are Strawberry anemones Actinia fragacea. Next a Plumose anemone Metridium senile followed by a white variety of the Red-speckled anemone Anthopleura ballii. I feed the anemones a couple of times a week by hand with pieces of defrosted shrimp. The anemones readily take up the shrimp, especially the Dahlia anemone is very quick to grab food and close up. The Plumose anemones are more difficult as they are often closed (they slowly open up when they sense food in the water but often they don’t) and have very fine tentacles not suited to feeding on larger particles. They would be better fed with zooplankton from a turkey baster but I have been too lazy to do that. When they are fully extended they are beautiful, white or orange but often they are flat as a pancake and shift shape a bit, leaving behind pieces of tissue that sometimes develop into tiny anemones. I have some beadlet anemones and a small orange and white species I am not sure of too. There are a whole bunch of other species (I can recommend this excellent guide) and many are very beautiful (see here for a gallery of photos by Paul Kay). The plan is to try to find more Dahlia anemones, as these come in many colour variations, but they are not very common in the rock pools here. A common species when snorkelling in the Helford is the Mud sagartia, which would also be nice to have. I am doubting about getting some Snakelocks again: they are very pretty and I could get the commensal spider crab as well, but they are also quite deadly…
a weird mollusc in Mylor Marina
In the series ‘pontooning‘, I returned to Mylor a week ago Friday to have a quick look around in the marina. The water was choppy, but visibility on the sheltered side of the pontoons was OK. I noticed a brown slug-like thing flapping about next to a boat. My first thought was a sea hare (I have seen plenty but have not yet seen them swimming). Upon closer inspection, I saw that it was something else, it had a shell like Haminoea or Akera, species I had never seen, especially not swimming. It turns out that it was Akera bullata, an Ophistobranch mollusc that is rarely seen in Cornwall and generally is observed crawling on the mud, not swimming. Why they swim is not well understood, but they usually swarm in numbers and so there must be some general response to the environment or mating behaviour going on. I saw four other individuals nearby so that fits. I made a couple of movies but as I could not look through the viewfinder the footage is not great (I went back Saturday and Sunday to try and find them back but was not able to). The shell can be clearly seen hanging down (Akera is related to the Sea hare but has retained its external shell). When lifted out of the water, the animal folds its mantle around its shell.
There were some other interesting things to see. The dominant organism on the pontoons is the tunicate Cione intestinalis (I see there are some other tunicate species hiding in these pictures; I will have to take a closer look next time). Amongst it grows the purple invasive Bryozoan Bugula neritina. Next, a colonial tunicate thta could be Botrylloides violaceus, Trididemnum cereum or Didemnun maculosum (or something else again). After that, the beautiful Lightbulb sea squirt Clavelina lepadiformis.
Plumose anemones Metridium senile are always common here. I for the first time noticed another species Diadumene cincta, very pretty! 
Aquarium Update 8
Another long time without a post. A lot has happened to the aquarium and some of what I post here is already outdated, but here goes. My Daisy anemone has buried itself and has not resurfaced but the Red-speckled anemone is growing well. I found the Dahlia anemone I was looking for, but lately it has been pestered by a Purple top shell, which has left a scar on its column, I hope it survives. The most dramatic event was that the Snakelocks anemone managed to kill my Sea scorpion (but not eat it, it was too large). This must have happened when IÂ removed some of the rocks, startling it and make it swim in the wrong direction:
Poor thing (although it had eaten 22 of my mullet so it works both ways I guess…). The good thing was that I could try keeping some other fish again. Using my net, I caught some Two-spotted gobies as well as a Common goby Pomatoschistus microps (I think, there are some very similar species) and a Goldsinny wrasse Ctenolabrus rupestris. The total tally from netting off the Flushing quay is now eleven fish species, not bad. The Goldsinny swims around the tank a lot and does some digging; it seems to be a more interesting fish to watch than the Corkwing:
The Plumose anemones Metridium senile are strange, they can be all shrivelled up for days, be short and squat or all extended. Here three pics of the same individual:
The Turban top shells Gibbula magus are very nice to watch (the Grey topshell Gibbula cinerarea gives a sense of scale). I found a Sea urchin Psammechinus miliaris and decided to try it out. It spends half its time under the gravel and pops up here and there with shells and pebbles attached to it. Let’s see what it does! Lastly a picture of the tank. I had attached a young Sugar kelp Saccharina latissima to the tunze pump with an elastic band and now it has attached itself to the plastic.
Aquarium Update 7
Long time no post, just been too busy! The aquarium is doing reasonably well at the moment, especially considering the fact that I have not done any water changes since the last update and I have added a bunch of new organisms. I have added two Beadlet anemones Actinia equina. They are a dullish brown (except for a nice blue band around the base); I have not found the bright red or green individuals yet. Very similar but more striking are Strawberry anemones Actinia fragacea of which I have collected three. They are voracious, I could easily feed them a shrimp a day. The same goes for the Sea scorpion. I am afraid of sticking my hand in now as it comes after me! Time to let this buddy go. This will also give me the opportunity to add some other things such as squat lobsters.
I have taken a break from experimenting with seaweeds and am focusing on anemones instead. I have added a bunch of small Plumose anemones Metridium senile that I scraped of the side of a pontoon. Weird fellas, they can fill up with water to be quite large, or just reduce to a crumpled little pancake. I have four white ones; I could only find very small ones of the orange variety and these were all devoured by Cushion stars (interesting). I’d like to have a large orange one as well, but I have to wait half a year until I can go diving again (they are very common in deeper water).
On the sheltered, silty shore of Flushing I found two small anemones attached to rock and half buried in the maerl sand. My excellent Seasearch Sea Anemones and Corals guide told me they were a Daisy anemone Cereus pedunculatus (uniform greay with many very short tentacles) and a Red speckled anemone Anthopleura balli (purplish and speckled, for a better picture of a different colour variant see this old post). Both quickly half buried/half nestled themselves under a rock so only the tentacles and the mouth are visible. They take pieces of shrimp and so hopefully they’ll be able to grow; these species should reach a decent size: 
My friend marine biologist Chris gave me a snakelocks anemone that he had cured from its symbiotic algae. A very cool, bright white individual but it has returned to its original purplish colour so it must have taken up symbionts again. The snakelocks I already had, grew big, split into two and grew some more. Interestingly, one of the individuals seems to be turning from the green- to the purple colour variety:
So six anemone species in all. I would really like to have some Dahlia anemones, they are very colourful, large, and not uncommon (old pic here). I need to go anemone hunting at a good low tide soon (I have not been out in ages).
I had the Chryseminia seaweed growing attached to the Tunze for a while and it worked OK, but it looks a bit messy and so I will remove it. However, I see that little Chryseminia plants have started to grow from the rock in many places (see top picture). I have to give the glass a weekly clean (with a tooth brush) and the rocks have turned a bit too greenish recently. I have noticed however that near the Snakelocks anemones, tufts of filamentous algae have appeared, as the grazers do not want to come too close to their tentacles (this reminds me of a work by an ecologist friend of mine who studies how seedlings can be protected from grazers when growing close to thorny shrubs, I’ll have to tell him of this observation!).
There has been some snail mortality. I mainly have Grey top shells but there are less than half of them left. I do not know why, part might be predation (which is not all bad as at least they serve as food for other inhabitants). I need to collects some more in any case. The Netted dog whelks are doing well. They are usually hidden below the sand, but as soon as they smell a defrosted shrimp, they come up like a Shai-Hulud. Their plowing through the sand is definitely good in preventing mats of diatoms to appear. Their little cousins the Thicklipped dog whelks are also doing fine. They tend to creep up the Daisy anemone to steal its food. I still have a Sting winkle Ocenebra erinacea which moves slowly but is very pretty. There are a variety of other species such as Blacklined- and Rough periwinkles. The best species however are the truly sublittoral large Turban top shells Gibbula magus (some of which have died as well, one of the shells has been taken over by a hermit crab, wich are also doing fine):
Pontooning
Unfortunately, the weather turned before I had another opportunity to go diving (or snorkeling). The wind and rain have reduced visibility too much and so I’ll have to wait half a year or so before conditions improve….too bad! I missed the low tides recently as well. However, today there was time for a bit of ‘pontooning’, i.e. lying flat on a pontoon and staring at the creatures attached to it. It is quite convenient as it is not dependent on tides and the communities are very different from that of rock pools. There is a very large marina at nearby Mylor Bridge that I had visited before in summer. There was a bit more life then (schools of mysid shrimp, more seaweeds, more tunicates) but it is still looking nice now. I used my iPhone to take pictures before, but holding it above the water was tricky and did not produce good results so I brought my new Canon Powershot instead (still not easy to take pictures as at the same time I had to prevent my two-year old son falling in the water). The bulk of the biomass hanging from the pontoons consists of tunicates (mainly Ciona intestinalis). Small Plumose anemones Metridium senile are common (more about those in the next aquarium update), as well as the sponge Sycon ciliatum. I even found a small Elegant anemone Sagartia elegans (var. venusta). The invasive Bryozoan Bugula neritina is very common; it looks a bit like seaweed even though it is an animal (see here for a description). Finally, the Peacock worm Sabella pavonina is common (and very striking). Just two pictures below as the rest was subpar; I have to go back on my own sometime soon maybe.
Aquarium Update 5
It was high time to get some rocks in the aquarium; always a bit difficult to do this aesthetically I find. Perhaps I should add some more but for now there are at least surfaces to hide under or attach to. I removed all seaweeds except for the fast growing Chrysymenia wrightii (I have had to prune parts of it already so it might act as a good nutrient sink). It is bright red and there are very few algae on it now I’ve placed it downstream of the Tunze pump. I will not add anymore seaweeds but instead wait for them to naturally settle and grow from the rocks. Tired of die-offs and algae problems! 
I replaced the first Sea scorpion with a smaller individual. I’ve decided to go for more sea anemones, which means it would be cruel to have small fish (juvenile Corkwings or Two-spotted gobies) around, so I might as well have large predatory fish in there as well. I hope to catch one or two more Sea scorpions (they’ll have to be similarly-sized otherwise they will devour each other). I will make sure I always have some shrimp in the tank to serve as live food (they are fun to watch in their own right of course). I will also add another Snakelocks anemone. It would be nice to also add a commensal Leach’s spider crab but I am afraid it might get eaten by the Sea scorpion so I’d better not. I have added a couple of white and orange Plumose anemones Metridium senile (I found them on a pontoon, more on that in a next post).They are quite small and sometimes shrivel up, so I have been handfeeding them pieces of defrosted shrimp and they already look better. I will try some Strawberry or Beadlet anemones too; other anemone species are hard to find when not diving (although that hopefully wil happen soon too!).
An Bollenessor 