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Pleurobranchus membranaceus

(Montagu, 1815)


Keith Hiscock Here is a picture of Pleurobranchus membranaceus leaving its eggs on the seabed at West Hoe, Plymouth Sound on 5 May 09. Enough bits-and-pieces to give a scale.

David Kipling Can you add that directly to the Egg ID album Keith, please?

Message posted on Seasearch Identifications on 16 May 2012
Gary Cobb This was posted earlier and is Pleurobranchus membranaceus

Gary Cobb A noyce critter!

Erling Svensen And what about this 10 cm big Pleurobranchus membranaceus? I have never, never seen anything like it. Before I have seen some that were 2 - 3 cm big, but 10 cm - never. I have a feeling that he have been out swimming. The snail was laying upside down on the seabead.

Tony Gilbert These are quite large Pleurobranchs, and are probably locally abundant within W. Scotland, where we've seen them in sea lochs. Their egg rings form a large spiral. http://www.flickr.com/photos/tonyjgilbert-images/3929313603/in/set-72157630248242222 Not sure of the distribution for these, but further south from Med. to Canary Is., you get the Umbraculum umbraculum, which can grow to about the same size.

Message posted on NE Atlantic Nudibranchs on 24 Jan 2013
George Brown What laid this 50mm long spiral of eggs on shell sand?

Chris Barrett Where was it found? Some elasmobranchs lay eggs like these

George Brown Hi Chris Barrett. Found on a gentle slope of shell sand, Les Dents, Sark. If you zoom in hundreds of tiny eggs can be seen, each the size of a pin head. They look suspiciously like mollusc eggs. Please excuse my ignorance but I thought elasmobranchs laid "mermaid's purse" like eggs? The egg mass in the photo is extremely delicate.

Chris Barrett I think it depends on the species. Elasmobranchs like dogfish and also skates and rays lay the mermaids purses, but i think species like Horn sharks lay the spiralled eggs. Not familiar with species of Sark though, so don't know if you get many sharks there. Like you say though, could just be mollusc eggs, especially given the size! :)

Chris Barrett I was thinking of things like this, although they're much bigger: http://www.google.co.uk/imgres?q=shark+egg+spiral&um=1&hl=en&safe=off&sa=N&biw=1366&bih=643&tbm=isch&tbnid=lkgy8a-iXc5X1M:&imgrefurl=http://www.nmfs.noaa.gov/rss/podcasts/weirdfins/sharkspurse.htm&docid=H44r1pXKl9o3SM&imgurl=http://www.nmfs.noaa.gov/rss/podcasts/weirdfins/images/Horn_shark_egg_case.jpg&w=432&h=432&ei=n4CyT6j7G4i18QPe8fGbCQ&zoom=1&iact=hc&vpx=202&vpy=136&dur=1132&hovh=225&hovw=225&tx=131&ty=91&sig=104821394047395528907&page=1&tbnh=139&tbnw=189&start=0&ndsp=18&ved=1t:429,r:0,s:0,i:72

David Kipling I've seen those spirals as well and had assumed some mollusc (based on no evidence other than looking like nudibranch eggs!).

David Kipling Pleurobranchus membranaceus lays eggs in spirals somewhat like this (see post by Jim Anderson). http://www.seaslugforum.net/showall/pleumemb

George Brown Hi Chris. Excellent image but I think you could drill for oil with that! The spiral is much more like what David suggests. Jim's beautiful images of Pleurobranchus eggs look more "bloated" but his correspondence with The Sea Slug Forum suggests they "take on water". Maybe they've just been laid? Having said that and the eggs exhibiting the same "left-hand" thread, I'm familiar with Pleurobranchus (and their eggs) but didn't see any in the immediate neighbourhood.

Jim Anderson This doesn't look like P. membranaceus to me from the size of the sand grains stuck to it ad the general shape.

Jim Anderson Maybe Cumanotus beaumonti (Eliot, 1906)

Jennifer Jones Okenia aspersa spawn?

David Kipling Thank you Jim, I was racking my brain trying to remember! I knew it was something exciting; I'd been advised to look for that nudi if I saw such spirals.

David Kipling Although looks a little different to the egg picture on SSF for C beaumonti: http://www.seaslugforum.net/showall/cumabeau

David Kipling The SMNR nudi survey has (as Jennifer suggests) pic of Okenia aspersa spawn that look like this, and they found a lot. See p21 of the 2010 report here: http://www.ccw.gov.uk/idoc.ashx?docid=da531252-994c-4a68-ad51-d23f209505a9&version=-1&lang=en

Kate Lock Yes I definately agree with Jen Jones - Okenia aspersa....we photographed both the nudibranch and loads of the eggs during the 2010 survey - very distictive corkscrew eggs usually found in sediment areas where Mongula oculata is found (O.aspera food)...

Kate Lock Glad to see our nudi survey report has been useful!!

Erling Svensen Are you sure about the Okenia? lokk here. http://uwphoto.no/shopexd.asp?id=1192

Keith Hiscock Yup, Pleurobranchus membranaceus eggs - 2008 was a 'good year' for them in Plymouth Sound - watched the slugs lay them and quickly scoot off at a rate of knots across the mud. Images available.

Kate Lock I shall check when in the Skomer office tomorrow - Bernard Picton was on the dive with us and took several pictures of the O.aspersa eggs - I have these on the files so can check them....think we could have some Pleurobranchus ones to compare too...

Erling Svensen I am quite sure it is Pleirobranchus

George Brown Looking at the evidence I'm with Jennifer Jones. All the Pleurobranchus eggs I've seen are much bigger and not as tightly coiled as the ones in my photo.

David Kipling I've seen these eggs also in Sark (which is where George took this pic) and my recollection is that they are smaller, thinner and a different spiral shape to the Pleurobranchus eggs that I've seen (and I know that's what they were because the adults were alongside). Actually, having said that I may well have some pics of the latter to help ... job for tomorrow!

Claire Goodwin Pleurobranchus eggs are much bigger and I think maybe a flat spiral rather than a coil (need to check pics!). I'm with Jen, Kate, George et al. in that these are Okenia aspera. We also have a similar spiral in the museum database from Okenia pulchella - though this is listed as a probable variety of O. aspera on Habitas (O.elegans are very different, orangeish and more tangled ribbon like).

Keith Hiscock I should have been more careful about scale and I am now (easily) persuaded that the eggs are not of Pleurobrancus as too small.

David Kipling Could someone post some Pleurobranchus egg pics in the folder so we have a comparison for future reference?

Kate Lock I have just put in the 'egg identification' folder a picture of each taken on the Skomer nudibranch survey 2010....we saw the beasties too so have proof of who laid the eggs! Hope this helps for future reference.

Message posted on Seasearch Identifications on 15 May 2012
Lucas CerCur Has anybody the probability to find Pleurobranchus membranaceus?

Egidio Trainito I do

Egidio Trainito Testudinarius obviously

Bernard Picton Yes, but not every year...

Craig Muirhead Yes. Found several dozen in Loch Fyne 2 weeks ago.

Lucas CerCur Great!

Lucas CerCur I think all of you have my postal address, isn't it?

Tony Gilbert Seems they like sea-lochs quite a lot, we also located many in Loch Nevis and Loch Hourn, plus the egg rings, perhaps its the right conditions and habitat for them. http://www.flickr.com/photos/tonyjgilbert-images/sets/72157630248242222/

Lucas CerCur Probably, would be possible to cut a little piece of foot of 1-2 living specimens, and to preserve these pieces in ethanol 96-95%?

Lucas CerCur The animals can be let in the see later. The pieces should be small, not big. Thus, the inferred damage is also small and the can continue their life. Photos of each aninal from which pieces anr taken will be needed also.

Lucas CerCur Collection data are also useful.

Message posted on NE Atlantic Nudibranchs on 20 Jan 2013
Taxonomy
Animalia (Kingdom)
  Mollusca (Phylum)
    Gastropoda (Class)
      Heterobranchia (Subclass)
        Opisthobranchia (Infraclass)
          Pleurobranchomorpha (Order)
            Pleurobranchoidea (Superfamily)
              Pleurobranchidae (Family)
                Pleurobranchus (Genus)
                  Pleurobranchus membranaceus (Species)
Associated Species