halcyon's picture

Unidentified creature

Observed: 28th August 2007 By: halcyon
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Description:

I originally posted this in Other Organisms. I'm posting it again here to Invertebrates to see if anyone here can help with identification.
I came across a few of these strange looking things washed onto the shore on a Brittany coastline, back in 2007. I've always wondered what they might be.
They are quite large - probably between 8 - 10 inches long, and have semi-transparent skin in some parts. As you can see in the pictures, they have a shiny dark rounded point at one end and are fatter at the other end, with a protruding part. There is a dark textured covering over part of them.
They're very alien looking and were quite disturbing to come across!

Identifications
Species interactions

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Comments

Nick Upton's picture

seaslug?

I still think it could be a notaspid seaslug, maybe family Pleurobranchidae, but am not sure what species it could be. P. membranaceus may be too small to be a match (up to 12 cms) if the original size recorded (8-10inches) is right. It's also really hard to guess what a balled up seaslug will look like from pics of them fully extended. Like Chris, I also considered a de-shelled mollusc of some kind but am not convinced it would look so intact or appear like this. Maybe someone out there knows more...

Nick Upton, naturalist and photographer.

ChrisMcA's picture

Tentacles

Tentacles Near the 'head end' to the right, you can see in the 'original size' in both pictures 2 white lumps,the larger nearer the front (=oral tentacle?)(& in 1st also see underwater their 'opposites'). In the 1st the little 1(= cephalic tentacle?) looks 'puckered in'; & in both the large ones seem to have an extension. So these seem like retracted tentacles /rhinophores

ChrisMcA's picture

Lots of Gastropods have 4

Lots of Gastropods have 4 tentacles at the front, including Pleurobranchus, Pleurobranchaea, sea hares, land snails & freshwater snails

Nick Upton's picture

Tentacles

I'd noticed those two which helped me think it was a gastropod and I'm still thinking it's some kind of large sea hare or seaslug, maybe Pleurobranchidae, but larger than P. mebranaceus if the recorded size is correct. halcyon might want to consider posting it on the this seaslug forum, where all kinds off odd looking seaslugs and sea hares get IDd and it looks quite simple to send a message and an image: http://www.seaslugforum.net/factsheet/sendmess If that happens, I hope any feedback is posted here. This is a good mystery....

Nick Upton, naturalist and photographer.

halcyon's picture

Good find Nick,I'll post

Good find Nick,
I'll post there and report back.
Best wishes,
Mike

EDIT: unfortunately, the forum there hasn't been active since 2010.

gramandy's picture

Only...

membranaceus and testudinarius recorded in med. One observation of forskalii in Israel 1977 (I like this one as it has the right colouration and size now). testudinarius is much more colourful and has network of lines on mantle which dont seem to be apparent here.

Nick Upton's picture

seaslugs

I'd come across P.forskali also and an image of a stranded one in this link http://www.seaslugforum.net/showall/pleufors has some overlaps with the image posted here, but the distribution doesn't seem right. I think only an expert will fully crack this / get us on the right track if we're not on it.

Nick Upton, naturalist and photographer.

dejayM's picture

maybe this

Just arrived and breathless...
Why can't this be a nearly digested Cuttlefish? Sepia officinalis is the right size and I was immediately struck, without reading comments or ID, that it was a cuttle bone.
Look at the skin here http://runswickbay.blogspot.co.uk/2013/04/cuttlefish-bone.html
and http://bkmcl.files.wordpress.com/2014/07/dsc008482.jpg
Here http://www.ispotnature.org/node/278415 even

Mike Kelly (halcyon) if you come back. If you add the Descriptive Tag ProjectM1 this post will be seen in the >>Marines Project<<
ðj

Nick Upton's picture

Cuttlefish???

An intriguing suggestion and the "partly digested" idea would explain the lack of tentacles and frilly edge… but for me it doesn't explain some of the structures that are visible, not that I can make full sense of them. Still a mystery??? or do others buy the Sepia suggestion?

Nick Upton, naturalist and photographer.

dejayM's picture

Looking back

Looking at your side-gill ID cold link>>here<< Nick, I can see why you were feeling a little confident - it is remarkably similar, albeit probably of USA origin.
Pleurobranchaea http://www.gbif.org/species/2302605
maculata to 10cms
inconspicua 5cms
mekelli 10cms http://doris.ffessm.fr/fiche2.asp?fiche_numero=1773
Pleurobranchaea californica 10 inches http://slugsite.us/bow/nudiwk80.html (Pacific sp)

None of the above seem to appear in the eastern Atlantic but even if they did, they'd have to be in numbers to fit halcyon's description.
I do concede, however, that the likelihood of Cuttle being semi-digested in numbers is even more unlikely!

Nick Upton's picture

Notaspids

Thanks for checking the links and seeing where my idea came from… For me, some kind of Notaspid seaslug, maybe Pleurobranchaea sp. seems most likely , despite size and distribution issues making a species suggestion hard. If it was just one (e.g. P. forskali, meckeli, membranaceus or testudinarius, all with Mediterranean records, though H. meckeli and testudinarius are also recorded from the Atlantic coast of Spain (Huleva) here: http://www.mediomarinohuelva.es/gastropoda/) maybe a major storm/ strong current could have brought it from where they are known, but the fact a few were seen makes that less likely, but still maybe possible. Or the distribution of some species has been poorly recorded and they are moving more into northern European waters, but maybe in deeper water than is normally sampled (P. meckeli recorded at 23m in one record I found). Still waiting for a seaslug expert who knows the side gills to notice this record and comment!

Nick Upton, naturalist and photographer.

dejayM's picture

moving on

Yep, I spent an age on the webthing earlier.
iSpot ZA has a number of people who might help and I have dropped a comment with Peter Southwood who might come.
http://www.ispot.org.za/search/node/pleurobranchaea
D

Nick Upton's picture

Expert input….

Great idea; let's hope he has a look. And even if I'm on the wrong track, he may have some new ideas!

Nick Upton, naturalist and photographer.

Pbsouthwood's picture

Not an expert.

Sorry about that. Just spent a lot of time in the water.
Nevertheless, my 2c worth.
I looked at the photos for quite a while, and could not see anything to convince me that they are pleurobranchs or cuttlefish.
My impression is that they remind me more than anything else of shucked abalone. Not in so much the general layout, but in the textures and colours. Are there any limpets in that region which would be big enough?

Peter Southwood.
Southern Underwater Research Group
Photos licensed https://creativecommons.org/licenses/by-sa/3.0/

dejayM's picture

shucked abalone

Goodness!
I suspect abalone is far too small to fit the description but it figures that the shells may have been removed commercially - Nick?
>>Nice pics<<
General distribution http://www.gbif.org/species/2293076 (Haliotis tuberculata)
Hey, thanks for coming Peter.
Back to your lovely warm Spring!
ð

Nick Upton's picture

Mystery remains?

Good to get some feedback from someone who knows his seaslugs, to rule out some possibilities and to get a new idea. Would never have thought of Abalone and can see the general look of a shucked one has some similarities, though I'm still not sure how the details of this specimen match up. I also doubt the Green ormer H tuberculata - the likely French species - find would be big enough - 12cm shell max, if the original report got the sizes right.

Nick Upton, naturalist and photographer.

dejayM's picture

More..

Maybe we should note that there is a second post, possibly of the same creature, here http://www.ispotnature.org/node/449091