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Archidoris pseudoargus

(Rapp, 1827)

Rob Durrant Presumably this has to be Archidoris pseudoargus. But the gill circle seems remarkably uniform, unlike any specimen I've seen before. The second pic shows the change after I had touched it. Would not be possible to extract from deep crevice without injury. Any observations, please?

Thorleif Sørvik i

Thorleif Sørvik Hello Rob. in some years i have a pare of them in my aquarium . they was laying eggs and it seem like they enjoyed .

Rob Durrant Hi Thorlief. I always enjoy finding this species on my local coast, because they come in such a range of colours and patterns. I have found that they are are very inclined to stay at the same site, within a very small area, for months on end. Sometimes one, but with a succession of partners.

Thorleif Sørvik yes i agree, in that they keeping partners, and they are wery freindly against each other. i seend 2 picture of them

Ian Smith Facebook has the annoying habit of choosing the order of images uploaded at the same time. Rob I guess your "second picture", showing gill withdrawal after touching, is on the left, above. The one on the right shows expanded gills, but flaccid as not supported by water. When uploading to an album I find that if images are uploaded and saved one at a time in the order I want them to be viewed, the order is preserved on screen. Not sure if it works when loading a couple of images not in an album.

Rob Durrant I agree, it is annoying, Ian, and that reversal often happens if you click on an image to view it; but in this case they are displayed correctly on the page. It is the opposite to your description. The one on the left as I am viewing it now, shows the gills looking like a uniformly pink something adhering to the body; whereas on the right is the pic (with a bluer hue) is after touching, showing a thin pink circle surrounding a central area of a different colour. As you say, in neither case supported by water.

Ian Smith expletive Fbk!! The views you and I are receiving are reverse of each other.

Rob Durrant Agreed re FB! That makes sense now :D In the many previous specimens of Archidoris I've seen, the gills were more clearly gills, more flowerlike, and obviously part of the animal; but I was puzzling over this one, which is why I touched it. Perhaps it was just that I couldn't quite get near enough to study closely, and had to rely on torch and flash images.

Rob Durrant Should have said thank you, Ian, for explaining what was going on - expanded gills, then gill withdrawal - since it was to find out such things that I posted this in the first place! I presume that by having its gills expanded it helps to retain moisture within them for better physical equilibrium between the tides.I will avoid touching the gills in future.

Message posted on British Marine Mollusca on 08 Nov 2013
Tine Kinn Kvamme From today´s dive. I believe this is: Archidoris pseudoargus Drøbak in the Oslo Fjord, Norway. Canon G12, internal flash + handheld torch.

Tine Kinn Kvamme The gills

Gary Cobb I think you are correct. The new name is now Doris pseudoargus

Tine Kinn Kvamme Love the quick response from you, Gary :-)

Gary Cobb Thanks Tine!

Simon Parker While I'm at it, I had this down as Cadlina laevis but I'm now wondering if it's another small Archidoris pseudoargus. Same site again; it was quite the nudi hot spot!

Simon Parker Yes, another 2 cm one.

Message posted on EPAM Nudibranchs on 11 Jul 2013
John de Jong Doris pseudoargus ?? at Zeelandbrug, Oosterschelde. 27-08-2012 with Olympus E330, 50mm macro, 1/100s, F18, ISO400 with 2x Ikelite DS160/161

Peter H van Bragt No, I think it is a Geitodoris planata just an uncommon colour variant. Cheers, Peter H van Bragt

Ian Smith Hi John I think this might be a pale Geitodoris planata. The tubercles seem a bit smaller than those on Archidoris, the mantle skirt is spread out nearly horizontal, there seem to be paler areas round large tubercles (acid producing on G. planata) . The clincher would be dark mars on underside of mantle. Oh, Peter has just beaten me and agrees. Have a look at the full description at http://www.conchsoc.org/spaccount/Geitodoris-planata Groetjes Ian Smith

John de Jong Thnx, Peter H van Bragt and Ian Smith. I thought I got a new one :-(

Ian Smith Location, location! I've never seen a live G. planata; the description was with photos and advice from Malcolm Storey who found the specimens shown on the web page. There were hundreds of of Archidoris pseudoargus spawning on a shore of the Menai Straits in Wales last March. Rhaid iddi ti ddo^d i Gymru (You must come to Wales :-) Ian Smith

Peter H van Bragt Hi Ian hop over the ditch. We do have them available in the southwestern estuary of the Netherlands. Although now less common as they used to be. In 2003 I had one dive with over 450 specimen and a max. size of 12 cm. Good old days ;-)

Ian Smith Hi Peter That's a big Geitodoris. I'll alter the Conch Soc account to allow for it. Ian

Tony Gilbert To me this looks like Archidoris psuedoargus. The colouration is that of a sea lemon, not G. planata which are usually brown. Check your images of this as G. planata has 10-12 stellate acid glands on the mantle, so your specimen needs these for id. Additionally, Bernards information indicates no records exist in the North Sea for this. The G. planata specimens I've seen have always been on west coasts. http://www.flickr.com/photos/tonyjgilbert-images/7501724518/in/set-72157630420768730

Ian Smith Hi Tony, have a look at http://www.diverosa.com/categories%20NL/ff%20naaktslakken.htm on it there are unmistakeable Geitodoris from East Scheldt estuary, branch of N.Sea. One is so low profile it looks like it's melted over the substrate. Another clearly shows the purplish peppering on the stem of the rhinophore. The tubercles are right for Geitodoris on these photos and on John's. Also Peter says he had 450 in one dive. Morphology is much more important than colour, but you can make out the pale acid papillae on John's specimen even though it is a pale specimen. The most decisive colour factor is to look for the dark marks on the under side of mantle and upper surface of foot on Geitodoris. Check out the conch soc description (link on my earlier message), it raises the possibility that Geitodoris is overlooked as A. pseudoargus in Britain. Cheers Ian

João Pedro Silva An example of a very flat G. planata: http://www.flickr.com/photos/jpsilva1971/6578495629/

John de Jong I will search him next week, and make some pics from the underside. First - have to find him ofcourse........

Ian Smith John I have just looked at Peter's excellent messages & photos about Oostschelde Geitodoris on the Sea slug forum: http://www.seaslugforum.net/find/5126 It seems from his photos that the dark marks, while present on the underside of the mantle and upper surface of foot of Dutch specimens, they may not be as heavily marked as on the British ones shown on the Conch Soc site. Cheers Ian

Ian Smith Joao have you any suggestions on how to separate Geitodoris planata from 'Doris' stellata, apart from radula dissection? I've seen several Mediterranean shots of slugs identified as stellata, but I find them difficult to distinguish on external appearance. Do you on the Atlantic-Med corner have experience of both species? Thanks if you can help. Ian

João Pedro Silva Ian, the only truly safe way to distinguish them is through the radula. But, at least aroung these parts, G. planata appears to show a more regular pattern on the mantle than Discodoris stellifera. Both show dark spots on the underside of the mantle. http://www.flickr.com/photos/jpsilva1971/6824858576/

Message posted on NE Atlantic Nudibranchs on 31 Aug 2012
Erling Svensen Have anybody seen the Onchidoris muricata with this kind of colour before? (I hope it is O. muricata?)

David Kipling What is the blue and orange thing in the bottom left corner Erling?

Jussi Evertsen The purlpe and orange colors are the stomach contents shining though the animal - this varies depending on what ectoprocts it has been feeding on

Erling Svensen I do not know, David. I have the high res. picture, and I have been looking. It is so strange. May be an alien? ;-)

Bernard Picton I think this might be a juvenile Archidoris pseudoargus. The tubercles are too numerous and the rhinophores the wrong shape for Onchidoris.

João Pedro Silva Just a few days ago Cláudio Brandão posted a photo with a purple tinged Archidoris/Doris pseudoargus: https://www.facebook.com/photo.php?fbid=373832925982153&set=o.166655096779112&type=3&theater

Bernard Picton Now we can have a debate about whether to call them Doris, João. I'm against unnecessary name changes by creating huge genera at the present time when we know the phylogeny can be worked out using DNA in a few years... At that time we'll be able to name clades more objectively.

João Pedro Silva I agree with the principle (like the Cuthona/Trinchesia "issue"), Bernard, although I'm not qualified to get into that debate :)

Message posted on NE Atlantic Nudibranchs on 28 Mar 2012
Robert Eriksson

Robert Eriksson Following Erlings discussion below. Pale A. pseudoargus, G. planata... Or?!

Klas Malmberg Aquatilis I would say G. planata because o the starlike symetrical spots?

João Pedro Silva Here in Portugal we have another similar species, Discodoris stellifera, with the same star shaped marks. I agree this is most probably G. planata.

Bernard Picton Robert, yes, certainly this is Geitodoris planata. You are right, the mix of small and large tubercles is more or less the same as in Archidoris pseudoargus. The gills directed to the rear is very typical of Geitodoris. Joao, I'd love to hear how you distinguish Discodoris stellifera....

João Pedro Silva Bernard, in the next hour or so I'll be posting one of today's photos showing D. stellifera. I made a couple of photos to show the brown spots one the underside on the mantle edge and also showing the large oral tentacles.

João Pedro Silva Hmm, same in G. planata. Maybe we should check the radula? Anyway, we collected it.

Message posted on NE Atlantic Nudibranchs on 29 Feb 2012
Erling Svensen Could this flat nudy be a Jorunna tomentosa? Its on a rock with a litle silt on it. I saw some tiny J. tomentosa during the dive, but this one (if it is J. tomentosa) was aprox. 2 cm long.

Christian Skauge I don't think so... the Jorunna should have more spiky, almost hair-like tubercles - these seem more rounded. Could it be a juvenile Doris pseudoargus?

Robert Eriksson Look at the acid glands. I'd say a starved geitodoris planata because of the few "glands". They appear more round when not moving and therefore atypical compared to e.g. Thompson o brown 1984.

Bernard Picton I agree with Christian, I think Archidoris pseudoargus (can't bring myself to call them Doris yet!) The mixture of rounded smaller and larger tubercles is just right. I don't think those are acid glands, Robert, but I don't know what they are.

Peter H van Bragt Considering the mix of relatively large and smaller tubercles, I agree with Bernard. On few occasion we also found such pale individuals on the Dutch coast.

Robert Eriksson I am not convinced. I have one photo of what I regard a G. planata. There are several characters which are different from A. pseudoargus; bilamellate mantle for instanstance. Had a discussione with Jussi regarding this... se my obsolete opisthobranch webpage... http://web.comhem.se/~u93824250/ob/

Robert Eriksson I see that this one has crenulated edges round the rhinophores. My photo shows no such character - has anyone read the species description of G. planata and A pseudoargus lately? I would say that crenlutade edges is a very stabile trait, in contrary to "spots", "brown colour" or "flattened shape".

Message posted on NE Atlantic Nudibranchs on 28 Feb 2012
Simon Parker This was in about 4m inside a cave near Eyemouth, Scotland. It was close to a Cadlina laevis but I didn't think they came in yellow? Rostanga rubra?

Vinicius Padula Bernard Picton

David Kipling Immediate thought would be an unspotty Archidoris pseudoargus. Rostanga rubra is red with white sunglasses (sorry, marks between the rhinophores), neither of which you've got here.

Simon Parker Archidoris seems logical. I'm not used to seeing them this small. This was about 20 mm long.

David Kipling I guess the big ones have to start somewhere ...

Bernard Picton Yes, I think Archidoris pseudoargus. I've certainly seen plain yellow ones and the tubercles are right for that species.

Gary Cobb Bernard I am pretty sure this Doris pseudoargus. I thought Archidoris was replaced by Doris.

Simon Parker I hate to say it but WoRMS has it as Doris pseudoargus. Is nothing safe from name meddling?

Gary Cobb DNA is upstaging the way we are finding out the true species. These things happen. With time man discovers how, through new developments, to accurately ID an animal.

Gary Cobb It also seems Nudibranch Books out date as soon as they are published!

Message posted on EPAM Nudibranchs on 10 Jul 2013
René Weterings Geitodoris planata.....one of the "thousands" that can be found in the Eastern Scheldt at the moment in The Netherlands!

David Kipling Apparently it's supposed to have oral tentacles (not seen in A pseudo). Which I guess means flipping it on its back?

Niels Schrieken Correct David Kipling . But if you don't want to flip it over Geitodoris planata can be distinguished from Archidoris pseudoargus by the light coloured stellate patterns on the mantle (acid glands).

Niels Schrieken The third difference is that at the underside of Geitodoris planata there are brown spots on the mantle.

David Kipling (so we have to flip it again!). Can we see the acid glands in this picture Niels?

Niels Schrieken Yes at least four glands are very obvious. Between the branchial plume and the rhinophores.

Niels Schrieken :-). I am not sure if we should say to the divers to flip over all the animals they see.

David Kipling Me too ;)

Jim Anderson In the examples I have seen the top of the rhinophore tapers to more of a point in G. planata -it's a wee bit subtle but seems to be consistent. The star shaped acis glands are usually more obvoius. We saw many of this species at Loch Creran last weekend.

David Kipling I'm going to be obsessively looking at ever Archidoris pseudoargus I see now ...

David Kipling SSF has a useful pic showing those stellate spots, and some description of G. planata versus A. pseudoargus : http://www.seaslugforum.net/find/geitplan

Brendan Oonk Try to flip some of the pics over ;)

Jim Anderson René, Lovely image - they are difficult to 'catch' with the gill and rhinophores on show.

René Weterings Thank you Jim, but there are so many of these nudi's right now, that it makes it a bit easier to "catch" them in a nice position for photography!

Bernard Picton I'm very interested to know what they are eating. They seem to eat several species of Mycale (a sponge). In Strangford Lough Mycale similaris became much commoner in the last 20 years, followed by the appearance of G. planata, for which there were no historical records.

Bernard Picton http://www.habitas.org.uk/marinelife/sponge_guide/sponges.asp?item=C5540

René Weterings They eat "Mycale micracanthoxea" according to Peter van Bragt.

Bernard Picton Thanks René, I was interested to know if you had seen them on other Mycale species. 30 years ago we only found them on the bright red Mycale rotalis. M. micracanthoxea was only named in 1977 and I wondered if it might be an invasive species of sponge. I'm interested in observations of possible interactions between invasive sponges and tunicates and nudibranch predators.

Niels Schrieken http://www.anemoon.org/anemoon/spuisluis/2007/spuisluis/2001/011118.htm/?searchterm=Mycale%20micracanthoxea is showing the different characteristics of G. planata.

Peter H van Bragt Dear all, Mycale micracanthoxea is the only Mycale sponge found in Dutch coastal waters. It was most abundant in 1999 when G. planata first appeared in our southwestern estuary. Within 4 years the G. planata population exploded. We could locally easily spot 400+ individiuals on a single dive in the Eastern Scheldt and Lake Grevelingen. Some of remarkable size: up to 12 cm. Twice as large as reported in older literature. At that time the huge G. planata population almost completly depleted the Mycale population. Result was that in 2005-2006 G. planata almost completely disappeared, presumably due to food shortages, allowing the Mycale population to subsequently recover again. This recovery was supported by two relatively severe winters for which G. planata seems to be quite sensitive: 2009-2011. Bear in mind that the Netherlands is part of the northern distribution border of G. Planata and we have in the Eastern Scheldt and Lake Grevelingen a very extreme watertemperature window.: winter close to +1 degrees C. and in summer >20 degrees C. Only this year G. planata is quickly developing a dense population in the Eastern Scheldt again. At this moment >100 per dive locally already. Needless to say, at this moment Mycale micracanthoxea is very abundantly present again! Most likely the absence of predators and pathogens at the introduction in 1999-2004 contributed also to the populaion explosion and extreme sizes. Cheers, Peter H. Peter H van Bragt

René Weterings Thank you Peter!

Vinicius Padula Dear all, I have interest in study this species (G. planata). Could some of you collect 2-3 specimens?

Brendan Oonk Surely that will be posible. What do you need them for/(What is your study)?

Paula Lightfoot Hi, I'm just re-reading these interesting comments about Geitodoris planata as I've just been told of three records made on the Yorkshire coast in 2010 and 2012. I see there is a record from Brander Point St Abbs in 2007 although this record doesn't seem to have turned up on the NBN Gateway yet. Jim Anderson do you know if the St Abbs record has been sent to the Conchological Society? I'd be interested to know if anyone else has reports of this species on the east coast and what it might be feeding on here. The three Yorkshire records were found intertidally. Thanks Brendan Oonk for the brilliant photos showing the dark spots and oral tentacles, I am going to look very closely at any 'sea lemons' I find in future and these will be useful!

Jim Anderson Paula Lightfoot - I thought that I had notified them but may be mistaken. I have east coast (St. Abbs/Eyemouth) records of it from Oct 2004, August 2006, Jun 2007, July 2007 and June 2010.

Message posted on NE Atlantic Nudibranchs on 10 Oct 2012
Matthew Green Seasearching at Tefor Pier yesterday, loads of life, 7m visability and nice and sunny!

Liz Morris LUSH!! I had approximately 0.2m visibility off Porth Eilian last Friday... very disappointing, but also great to be in the water and excellently spongey :)

Mandy Knott Any other reports on the viz? Particularly Holyhead, Cemlyn and Porth Dafarch??

Rohan Holt Been excellent in holyhead marina. Although locally depleted due to eradication bags having all the poo emptied out of them.

Matthew Green Hi Liz, went to Porth Eilian yesterday (after working all morn on my EIA), it was 4m vis, should be similar or better today. Excellent dive! Tonnes of life. Lots of sea lemons (Archidoris pseudoargus) I will try and get tim to upload photos.

Liz Morris Cool - I've heard generally good viz comments Mandy. The trick with P Eilian is dont do it on a low water spring lol (when I did)!!! Still nice and spongy though!!

Mandy Knott Thanks everyone. Here's keeping fingers crossed for the weekend. North west group coming down for some qualifying shore dives.

Liz Morris Have fun Mandy Knott. Ps - last time we tried, Porth Dafarch was undiveable as there was a big slipway reconstruction going on, so access was too difficult for divers.

Message posted on Seasearch North Wales on 27 Mar 2012
Animalia (Kingdom)
  Mollusca (Phylum)
    Gastropoda (Class)
      Heterobranchia (Subclass)
        Opisthobranchia (Infraclass)
          Nudibranchia (Order)
            Euctenidiacea (Suborder)
              Doridacea (Infraorder)
                Doridoidea (Superfamily)
                  Dorididae (Family)
                    Archidoris (Genus)
                      Archidoris pseudoargus (Species)
Associated Species