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Philine catena

(Montagu, 1803)

Anne Bunker These tiny pink animals were found in Pembrokeshire on 21 September (Natural Resources Wales intertidal survey). The largest is approximately 3mm long. Mid shore rock pools on crustose coralline algae. Exposed shore (Pen y holt). We found them in the same rockpools 3 years ago. Can you help with identification please?

João Pedro Silva Limapontia sp. perhaps?

Christian Skauge Tiny Elysia viridis?

Peter H van Bragt Can you post a cropped, enlarged specimen. I think I see folded parapodia. Could be juv. Seahares??????

Christian Skauge Here's one, Peter H van Bragt. This is what made me think E. viridis - same basic bodyshape and spots on the back ;-)

Peter H van Bragt No rhinophores, so Elysia and seahare don't seem to be an option.

Jan Light Would the rhinophores be developed on such a young specimen?

Ian Smith Rhinophores appear at 3mm on Elysia. I guess Anne 's slugs are bigger, perhaps she could say? See http://www.conchsoc.org/node/5610 (Later edit; I see Anne said largest 3mm.)

Ian Smith Coralline pools on exposed shores have some real surprises. Runcina coronata can be abundant, and has some golden brown in good light, but the shape of these isn't right for it. The slugs shown have a rotundity with some whitish colour; I think this could be an internal shell showing through the mantle. All have a truncate end which, on those turned at the right angle, suggests the cylindrical posterior of the mantle covering the shell, as on Philine punctata http://www.conchsoc.org/spAccount/philine-punctata Christian's crop seems to show parapodia and a thin anterior without any features. The nearest fit to all this; structure, colour and occurrence in tidal pools, in Thompson Opisth Biol vol1 is Philine catena, max length 6-7mm, an uncommon and little-known species. Just a suggestion, but an exciting find whatever it proves to be.

Keith Hiscock Look like Runcina coronata to me. Rarely see them. Last time was at Pendennis Point, Falmouth in May.

Ian Smith Runcina coronata images at http://www.conchsoc.org/spAccount/runcina-coronata Frequent in coralline pools on exposed coast, and the obvious candidate. A good chance that Keith is right, but as I said above, Anne's look different structurally as far as can tell from image. Well worth further investigation.

Jan Light I know Runcina coronate, these animals are not that.

Ian Smith The more I look at the images, the more I'm inclined to reconsider Jan's idea of Elysia viridis before rhinophore development. The general shape is very like the juvenile Elysia image above. I think I MAY be able to make out stumpy early rhinophores on some of them - if only the images were clearer. Pink body Elysia would be expected on pink weed BUT it feeds by piercing individual cells of large celled weeds; do the juveniles have a feeding mechanism that can utilise encrusting Corallina ?? Intriguing.

Anne Bunker They were only on the encrusting coralline algae although there were a lot of other algae in the pools. I brought one back to examine under the microscope but I'm sorry to say that it died and became an amorphous mass about 2 seconds after I turned the microscope light on.

Keith Hiscock This is my pic. of Runcina coronata at Pendennis Point - any comments on confirmation/correction welcome.

Lucas CerCur Or...Runcina ornata

Lucas CerCur Runcina.....another European opisthobranch mess that should be solved.

Ian Smith I agree Keith; typical R. coronata, or whatever it turns out to be when the "mess" is sorted. I've found it in thousands in a single HW pool on exposed coast Anglesey, hundreds in pools at HW on fairly exposed shore Lleyn Peninsula, several in virtually every pool near HW on tip of Portland Bill. Several other records on NBN are from exposed coast. However I've also found it at LWS on sheltered sites such as inner Bay of Firth near Finstown in Orkney and a sheltered LWS pool in Lleyn. It's seasonal; the pool in Anglesey had none findable on a September visit. Could be that the exposed / sheltered ones are different segregates, but they all looked the same. If all one sp. I think it is catholic, but overlooked because of small size except when on contrasting substrate, such as encrusting coralline.

Lucas CerCur I consider (in this moment) that in UK there are 3 species of this genus, i.e. R. coronata, R. ornata and R. ferruginea. But, I think that a deep study should be carried around all Europe.

Ian Smith Lucas, can you tell us how to separate the three spp. morphologically and/or direct us to images on the web?

Lucas CerCur Even if in 2001 and 2002 two relevant contributions were published by Schmekel and Cappellato and several Mediterranean new species were described, all photos were in black snd white and many of non living material and both papers are based on anatomy and morphology.

Ian Smith Can you give us the references? Did they include British material? I'm aware that the Med. has more spp. from viewing Bill Rudman's Seaslug forum.

Lucas CerCur R. ferruginea is very easy, since it is reddish. The remaing two could be more complicate. In general, the typical R. coronata has two more or less evident white arches (half-collar), one below the head and the other before the end of the notum. Moreover, there are a lot of withish and very Little White punctuadion over the notum. R. ornata is like the Keith's photo.

Ian Smith Above, in this string of messages, I hazarded the possibility of Philine catena. By coincidence a friend has sent me a series of images of it from Croatia. None of them hold themselves in a tapered position; all have the wide truncated end shown in this image. So I think my suggestion should be dismissed. It looks as if young Elysia are the best bet.

Message posted on NE Atlantic Nudibranchs on 22 Oct 2013
Animalia (Kingdom)
  Mollusca (Phylum)
    Gastropoda (Class)
      Heterobranchia (Subclass)
        Opisthobranchia (Infraclass)
          Cephalaspidea (Order)
            Philinoidea (Superfamily)
              Philinidae (Family)
                Philine (Genus)
                  Philine catena (Species)
Associated Species