Mycale micracanthoxea

David Kipling One good deed deserves another? Here Geitodoris planata nudibranchs are keeping the top valve of a scallop clean of encrusting sponge. Loch Creran SAC in ~ 15m of water

Paula Lightfoot There are very few records of this species from the east coast - definitely none on the NBN Gateway although I know there are some from St Abbs on the Scottish Nudibranchs website. Two Yorkshire records have just been published in the YNU's journal The Naturalist, from Jackson's Bay Scarborough on 15th June 2010 and Burniston Bay on 10th May 2012.

David Kipling It was locally abundant in Creran - loads of scallops with encrusting sponge helps!

David Kipling I also wonder if it is under-recorded Paula - it does look a bit like Doris pseudoargus (bit flatter and more spread out) although the habitat gave it away.

David Kipling Two more examples from the same dive, better illustrating the "flat disc" appearance of this species compared to D. pseudoargus

David Kipling

David Kipling Paula - its distribution nicely mirrors that of one sponge suggested on Habitas as its food (Mycale rotalis) - although I think Bernard thought that the sponge on the scallops at Loch Creran was another (possibly undescribed) Mycale species. As always with nudis: find the food, find the nudi ...

Paula Lightfoot I know there are plenty of west coast records and that it is common in Loch Creran - well illustrated by your excellent photos and some similar ones on the Scottish Nudibranch website too. But just saying it would be nice to mobilise some of the east coast records onto the NBN Gateway :). This topic has come up a couple of times in the NE Atlantic Nudibranch Fb group too - with some excellent pics showing the diagnostic features (pale star shaped patches around acid glands and brown spots under the mantle if I remember right??) and some discussion about its various spongy food choices. I think it's mainly the younger specimens that can look similar to sea lemons.

David Kipling So where do those YNU records end up?

David Kipling As an underwater jizz thing, this species seemed to be flatter and more circular in shape than a sea lemon. It was certainly enough to make us think "eh? something's not right here" and take a photo.

Paula Lightfoot Records sent to YNU recorders or entered into our online recording website go onto the NBN Gateway in datasets administered by the relevant national recording scheme or local records centre - no problem. Our published data policy says that all records submitted will be shared publicly in this way so we don't need to get individual permission. At last year's AGM it was clarified and minuted that records included in articles sent to the journal are also covered by this data policy - in theory - the interesting thing will be whether that works in practice ;) Agree about the jizz, it looks like a sea lemon that's been squished. Lemon squash.

David Kipling * groan * :)

Bernard Picton This species was historically confined to the SW of the UK. It underwent a spectacular increase in the Netherlands after arriving there for the first time. It now seems to be doing well in Loch Creran. The sponge on the scallop is probably Mycale cf. contarenii, which used to be common on Aequipecten in Strangford Lough but is now almost extinct there after it was targeted in 1987-1989 by the Isle of Man fishing fleet and its nursery habitat of the Modiolus beds was almost destroyed. In the Netherlands I think it took advantage of the sponge Mycale micracanthoxea which itself was probably an aquaculture related introduction. What tangled webs we weave.....

Erling Svensen The Geitodoris planata from yesterday. I saw hundreds yesterday, and many between the Ciona. When looking at the pictures, I can see eggs. Do anybody knows if these are Geitodoris eggs?

Brendan Oonk The eggs of G.planata are ribbon shaped. For foto see website of John de Jong http://electest.home.xs4all.nl/Biologie%20Oosterschelde%20en%20Grevelingen/Zeenaaktslakken/Geitodoris%20planata%20(Millennium%20Wratslak)/slides/DSC06813.html

Erling Svensen OK. Thanks. Then I do not have any clue what these eggs are.

Peter H van Bragt Are you shure they are eggs???? Could it be possible that we are looking at developing Diplosoma listerianum (Tunicates) colonies? Are tehre better/detailed pictures available. Geitodoris planata was first observed in the Netehrlands in 1999. Ar that time there was an abundance of Mycale micracanthoxea. The G. planata population developed very fast and in 2001-2003 we found on occasions up to 30-450 speciemn per dive (75 minutes). At that time the sponges where rapidly depleted by scavenging nudi's and subsequently in the next year the G. planata population collapsed almost completely. At this moment we only occasional find them back in very small numbers. The sponge population is recovering again due to lack of predation. We have observed that G. planata also seems to be sensitive to severe winters. Cheers Peter H. Peter H van Bragt

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.