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Alcyonium digitatum

Linnaeus, 1758


Jon Chamberlain Any ideas what this purple fuzz is? Growing on Alcyonium digitatum, Conger Reef, Eyemouth, approx 15m on rock wall. http://www.flickr.com/photos/underwaterinferno/8088012571/in/set-72157631775493437

Marco Faasse Looks like Cyanobacteria.

Message posted on Seasearch Identifications on 15 Oct 2012
Tine Kinn Kvamme Tritonia hombergi crawling on it´s evening snack Alcyonium digitatum (Dead man´s fingers) Drøbak in the Oslo Fjord (Norway) Canon G16 in Canon housing, internal flash + handheld torch.

Message posted on UWphotographers on 08 Nov 2013
David Kipling Simnia patula from Falmouth area today, 20-25m depth, large numbers feeding on Alcyonium digitatum

Message posted on British Marine Mollusca on 06 Jul 2013
Jon Chamberlain I thought I would share this pic of a Tritonia hombergi, very common in the UK, mainly found on Alcyonium digitatum (dead man's fingers). They are usually 1-3cms long but this one was approx 12cms and moving across gravel. http://www.flickr.com/photos/underwaterinferno/8079898048/in/set-72157631752211790 The tropics have more than their fair share of stunning nudis, but this one is definitely one of my favourites. Depth: 15m, Temp 11 deg C, Longstone End, Farne Islands, UK

João Pedro Silva Every time I found Alcyonium digitatum I look for T. hombergi but no look until now. Probably a lot less common around these parts. Nevertheless, we do have another spectacular tritoniid: Marionia blainvillea :)

Jon Chamberlain At this time of year at the Farne Islands/St Abbs you would be hard pressed to find a piece of A. digitatum that didn't have them on! Here is another photo of what is the usual scene: http://www.flickr.com/photos/underwaterinferno/8088017992/in/photostream/ Depth: 15m, Temp: 11 deg C, Conger Reef, Eyemouth, Scotland.

Tine Kinn Kvamme Tritonia hombergi nudibranch. Drøbak, Norway. Canon G12, internal flash + torch.

Marlyse Gehrig Amazing ... (y)

Ron Silver size?

Tine Kinn Kvamme About 80-100 mm. I've read they can get to about 200 mm. Biggest nudi in the ocean here up north.

Ron Silver Thanx

Tine Kinn Kvamme I saw another just a week ago out and about measuring 130-150 mm. Quite a few egg spirals from them too.

Ron Silver What color is the egg ribbon? I've seen some correlation between color of the nudi (or at least its food source) and its egg ribbon.

Tine Kinn Kvamme They are big and white but not exactly like a ribbon. I'll find a photo for you :-)

Tine Kinn Kvamme These are eggs from the Tritonia hombergi

Ron Silver Wow. A pile of spaghetti. What does T. hombergi feed on?

Tine Kinn Kvamme You often find them close to the Alcyonium digitatum or the Dead man´s fingers which they feed on.

Tine Kinn Kvamme Yes, a pile of spaghetti sounds better than egg ribbon :)

Marlyse Gehrig Thx for all these so interesting infos ..!!!

Tine Kinn Kvamme You are welcome Marlyse Gehrig :)

Tine Kinn Kvamme Here´s the bigger one stretched out

Marlyse Gehrig not so easy to see or find ... Thx Tine Kinn Kvamme ..<3 so much

Message posted on UWphotographers on 29 Aug 2013
Erling Svensen I send in a picture from 16. of January. I saw this tiny litle nudy on a Alcyonium in Egersund harbour (South West Norway). Could it be a small Dentronotus frondosus, or what do you think? It was only 1,5 cm long.

David Kipling Baby Tritonia hombergii perhaps? Right food source.

Erling Svensen May be. I did not think of this one but I am quite sure this is correct.

Christian Skauge This looks like a Tritonia plebeia. You can tell them apart by the mouth part - T. hombergi has two broad veils, and not the tentacles dispolayed by the T. plebeia. Food is the same in both species - Alcyonium digitatum, dead men's fingers.

David Kipling Thanks Christian. I was looking at those distinct oral processes and it seemed a bit wrong for T. hombergii, didn't know about this other species.

Christian Skauge Although it is distibuted from western med to Norway, this a quite small (max 30mm) and inconspicuous species. Not many people see it at all, and when they do it is commonly percieved as a baby hombergi - have done it myself for years :-)

Bernard Picton I think young T. hombergi might have only a few tentacles on the oral veil. For me the colour of T. plebeia is quite different. http://www.habitas.org.uk/marinelife/species.asp?item=W12460

Marco Faasse Maybe Rob Maller has a photo of a white Tritinia plebeia from the Netherlands?

Message posted on NE Atlantic Nudibranchs on 03 Feb 2012
Jon Chamberlain I thought I would share this pic of a Tritonia hombergi, very common in the UK, mainly found on Alcyonium digitatum (dead man's fingers). They are usually 1-3cms long but this one was approx 12cms and moving across gravel. http://www.flickr.com/photos/underwaterinferno/8079898048/in/set-72157631752211790 The tropics have more than their fair share of stunning nudis, but this one is definitely one of my favourites. Depth: 15m, Temp 11 deg C, Longstone End, Farne Islands, UK

João Pedro Silva Every time I found Alcyonium digitatum I look for T. hombergi but no look until now. Probably a lot less common around these parts. Nevertheless, we do have another spectacular tritoniid: Marionia blainvillea :)

Jon Chamberlain At this time of year at the Farne Islands/St Abbs you would be hard pressed to find a piece of A. digitatum that didn't have them on! Here is another photo of what is the usual scene: http://www.flickr.com/photos/underwaterinferno/8088017992/in/photostream/ Depth: 15m, Temp: 11 deg C, Conger Reef, Eyemouth, Scotland.

João Pedro Silva Is this Tritonia plebeia? Os a juvenile T. hombergii? Found this morning in Sesimbra, Portugal, approx. 5m deep, water temp. 17ºC. ~5mm long. "Small detail": I know this dive site pretty well and have never seen Alcyonium digitatum there or nearby.

João Pedro Silva Another shot of the same specimen.

João Pedro Silva And another

João Pedro Silva

João Pedro Silva Any hints on this?

Brendan Oonk I would say T. plebeia. T. hombergii is usualy more wide and the gills on the side differ in size. This nudi is rather slender and the gills are all roughly the same size

João Pedro Silva Thanks, Brendan! I thought so but I wanted a confirmation as it's the first time I've seen this species.

Brendan Oonk My response is based on books, never saw T.hombergii

Klas Malmberg Aquatilis T. plebeia because of the fingerlike processes on the oral veil, 3-4 per side, T.hombergi has more and smaller processes and the oral veil is bilobed.

João Pedro Silva Thanks, Klas Malmberg! Brendan, until last February I also hadn't seen T. hombergii.

Message posted on NE Atlantic Nudibranchs on 26 Jun 2013
João Pedro Silva Yesterday I spent most of the dive looking for T. hombergii but none found. Lots of egg masses, though. Could these belong to some other species? Also, I know of no colonies of Alcyonium digitatum near that spot. Is it possible they also feed on other Alcyonium like A. glomeratum (lots available there)?

Peter H van Bragt Looks very much like T. hombergii spawn!

Bernard Picton I think they are quite nocturnal...

João Pedro Silva It'll be very difficult to organize a night dive in that place... and the weather forecast for the next few days are not the best. In fact, are close to the worst I've seen.

João Pedro Silva Regarding the food source, I'm still puzzled with the absence of A. digitatum in that place and yet with so many egg masses.

Gary Cobb Did you check under rocks?

João Pedro Silva This spot is the wall of Cape Espichel. It's hard rock wall with sandy bottom, no rocks small enough to even think about rolling. There's also a large wreck there, the River Gurara, and maybe it's hiding under some of its pieces (but they're all very large...). I'm more inclined towards it being hiding in holes in the rock wall. These shots were taken in a sort of cave (10-12m wide and maybe some 6m deep into the wall) and the egg masses were more frequent in the most interior parts and near the ceiling. The single individual I've found was rolling on the sand just outside the cave and found at the end of the dive (I was actually starting to inflate the SMB) and I suspect it fell from the ceiling after being dislodged by our bubbles (open circuit does have its advantages).

Message posted on NE Atlantic Nudibranchs on 28 Feb 2013
João Pedro Silva Lots of these eggs masses around today, mostly associated with Alcyonium glomeratum (I think...). Don't recall seeing them at this place before. Any idea on the "parents'" ID? Also found Tritonia hombergii for the first time today, rolling on the sandy bottom. No Alcyonium digitatum in sight, though.

Peter H van Bragt Where these spawn big and fat??? Could very well be T hombergii

João Pedro Silva Not sure how to handle "big" and "fat". They were rather big but the diameter was ~5-6cm. Some were slightly pink. http://www.flickr.com/photos/jpsilva1971/8448904534/ The single T. hombergii I found there was ~4-5cm long.

João Pedro Silva The size reminded me of the spawn of Dondice banyulensis but these are thinner and very different in shape: http://www.flickr.com/photos/jpsilva1971/5190093660

Peter H van Bragt Pink is often seen in T hombergii spawn. One can never be sure but it seems to be a candidate.

Jim Anderson These look like Tritonia hombergii spawn to me. I have a few examples here

Jim Anderson http://www.nudibranch.org/Scottish%20Nudibranchs/tritonia-hombergii.html

João Pedro Silva Thanks! I hope they're still around next week :)

Tony Gilbert Check out Tritonia plebia's spawn, if there are any piks for that. There maybe a subtle difference between the two. T. plebia likes A. digtatum, not so sure about A. glomeratum though.

Jim Anderson T. plebeia spawn is quite different and considerably smaller - see here http://www.nudibranch.org/Scottish%20Nudibranchs/html/tritonia-plebeia-spawn.html

Tony Gilbert Thanks Jim, always good to discount what is not.

Message posted on NE Atlantic Nudibranchs on 05 Feb 2013
Paula Young Help, help? Any ideas? This was taken a couple of miles west of Dover, about 18m. Initial thought was a squirt of some sort (comments from Mr Kipling, Becky Hitchin welcome).....possibly Didemnum maculosum...but I'm not entirely convinced and am just not that good with blobby masses??

David Kipling Looks like star shaped holes, so squirt with closed siphons would be good start. But in the back some look to be raising themselves up a little, and actually I can't see inside any of the holes. I've been caught withnthi

David Kipling ... With this one before with and intertidal "squirt".

Paula Young Another thought - There were lots of Alcyonium d. around, and I did come across one earlier in the dive with nearly all the polyps retracted (got over excited and thought it was some interesting nudi at first, but no...). I just thought maybe this looked a bit too bumpy or irregular to be Alcyonium?

Becky Hitchin one or two of the polyps do look like they have 8-fold symmetry. but that's squinting very hard and hoping

Paula Young What's DMF...apart from something I can do a kitchen makeover with? Oh no...hang on!

David Kipling Alcyonidium digitatum, the finger dead man's finger ;)

David Kipling No I was making word play on finger bryozoan (Alcyonidium diaphanum versus Alcyonium digitatum).

Paula Young I think DMF it is then...there were loads around! Thanks all!

Message posted on Seasearch Identifications on 10 Jun 2013
Taxonomy
Animalia (Kingdom)
  Cnidaria (Phylum)
    Anthozoa (Class)
      Octocorallia (Subclass)
        Alcyonacea (Order)
          Alcyoniina (Suborder)
            Alcyoniidae (Family)
              Alcyonium (Genus)
                Alcyonium digitatum (Species)
Associated Species