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Okenia aspersa

(Alder & Hancock, 1845)


Dan Bolt Okenea aspersa (?) as spotted by Alex Mustard today on the wall of Plymouth Breakwater fort. Hopefully Terry Griffiths can go back and find it again tomorrow!

Alex Mustard What a beauty, Dan. I didn't have the heart to post my shots of this beast! I'll wait until hopefully Terry has his tomorrow.

Terry Griffiths Not common in the south west down as Oban area and Skomer Island.

Lucas CerCur Yes, it is Okenia aspersa.

Message posted on NE Atlantic Nudibranchs on 05 May 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
Richard Yorke My pictures from last weekends dives off the Llyn now at http://www.richardy.co.uk/LlynSept2013/index.html

Shôn Roberts There are some really great photos there Richard. I think the photo of the Crystal Sea Slug is superb. (i think thats what it is).

Shôn Roberts Do you mind if I share your album on my facebook page ?

Richard Yorke No Problem at all sharing it. It is not a crystal sea slug, that is Janolus cristatus. If you look at the Eubranchus tricolor you will see that the tips of the cerata have white tips, then an orange band then white again. Compare that with a Janolus eg. http://www.richardy.co.uk/Doune2013/content/130721_103026_E-520_large.html and you will see the difference.

Shôn Roberts Thanks Richard.

Ruth Sharratt Lovely set of pics Richard - well spotted. I've not managed to spot an octopus this year, so I'm really quite jealous.

Ruth Sharratt Plus - A great picture of the eubranchus - you can really see the detail.

David Kipling Curious to see whether you and Liz and Franki thinks the following is a bivalve or an ascidian. It seems a tad bulbous, and has six-fold (hexagonal) symmetry around the siphons - bivalves always seem to be circular siphons. http://www.richardy.co.uk/LlynSept2013/content/130929_085938_E-520_large.html

Liz Morris I think it looks like a squirt to me. Too shallow. It has frilly siphons, and is 'clean between the siphons'. Is it possible its a Molgula? It is too big for M.oculata that Bernard Picton mentioned the other day?

David Kipling The anatomy of a squirt seems to result in geometric-shaped siphons (square, hexagonal or octagonal). I've never seen bivalves with geometric siphons. The frilly bit (the molgulid 'crown') suggests a Molgula (as does the fact it's buried).

Richard Yorke OK, had discussed this already with Liz and I will now make the change :-)

Liz Morris Please note... I didnt start the online discussion :)

Bernard Picton This looks like Molgula oculata. Well done Liz!

Liz Morris Great. We'll get there eventually with these squirts!

David Kipling So is this the one that Okenia aspersa eats Bernard?

Bernard Picton No I think it eats Molgula occulta. I'm also not sure whether Okenia pulchella is a separate valid species and whether Eugyra arenosa is also on their menu.

Wendy Northway great photos Richard

Message posted on Seasearch North Wales on 02 Oct 2013
Taxonomy
Animalia (Kingdom)
  Mollusca (Phylum)
    Gastropoda (Class)
      Heterobranchia (Subclass)
        Opisthobranchia (Infraclass)
          Nudibranchia (Order)
            Euctenidiacea (Suborder)
              Doridacea (Infraorder)
                Onchidoridoidea (Superfamily)
                  Goniodorididae (Family)
                    Okenia (Genus)
                      Okenia aspersa (Species)
Associated Species