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Ascidia conchilega

Muller, 1776

David Kipling Do bivalve siphons ever have regular spaced red dots on the end? Ascidian siphons often do (they're light sensing organs) and I was wondering if their presence made it a definitive "this is not a bivalve siphon" ID. This example from yesterday (in ~ 12m off Castlemartin Ranges in Pembrokeshire) shows a greenish siphon to the left emerging from the reef next to a compound ascidian. Note eight red dots.

George Brown This is interesting. I found something very similar a few days ago. Habitas ascribes Ascidia conchilega as having 8 red spots around the oral siphon and 6 around the atrial. It also has a greenish tinge.

David Kipling I think in this case it is indeed A conchilega (for exactly the reasons you say - they come in pairs and the other siphon has 6-fold symmetry). There were quite a few on the dive and we've seen them around there before - very noticeable green colour underwater. Sometimes has a stretched appearance too. But it made me wonder if any mollusc siphons also have the same red dots.

Liz Morris Theres a guy at Bangor working on venerid siphons, i'll send you his details.

Cynthia D. Trowbridge David, Light sensors? Ocelli or more sophisticated? WOW!

David Kipling In Ciona the red spots are termed OPOs (oral pigmented organs) and have been assumed to be photoreceptors (Ciona shows a photoreflex) although it hasn't formally been proven neurologically. They're also little stores of stem cells from which the siphon regenerates after being nibbled off. Bill Jeffreys works on this. I don't know how widespread these putative photoreceptors are; you don't see red dots in most species but that may not be that informative! http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3581043/

Message posted on British Marine Mollusca on 20 May 2013
David Kipling Apart from the greenish siphon to the right of Ascidia conchilega the rest of this picture is a mystery to me. Are these individual orange worms of some type? And what makes the tiny sand-covered tube with arms waving out shown in the blow-up?

Andrew Mackie Orange 'worms' look like gills to me. Maybe from a cirratulid such as Cirriformia tentaculata .

David Kipling Ah, I see now, so all from one animal. Thanks

David Kipling What about tiny waving arms?

Andrew Mackie The cirratulid gills could be from a Cirratulus. Wonder if the thin 'tubes' are faecal extrusions from a sabellariid?

Message posted on Seasearch Identifications on 08 Jun 2013
George Brown This has some characteristics attributable to Ascidia conchilega but it doesn't look quite right. Assistance with this would be much appreciated. NW corner of Eilean nan Coinean, Sound of Jura, depth 35m. Many thanks.

Wilfried Bay-Nouailhat Hi George, A. conchilega is attached by the left side and siphons are wide apart... I think that it is Ciona intestinalis with some carateristics of type A form of the species

David Kipling What is the poor thing doing half-hidden in sediment? Was there a landslip?

George Brown Thank you Wilfried. I think that makes sense. Any information regarding the "type A" of the species? The ascidian was growing up between the two valves of a dead razor fish.

David Kipling Type A is the more southern species, the northern-most limit being around the Channel. You get both versions in Plymouth and they are very very similar - Atsuko Sato has done some work there on hybridising the two together (they have different temperature shock sensitivities and so on) and looking at the genetics of this, so she got to be a dab hand at field ID of the two variants (confirmed by DNA sequencing after). Possibly because of geneflow between the two types in that area there was a bit of overlap in features, but the one thing that did seem to work was the presence of a tiny red dot on the tip of the sperm duct.

David Kipling Have a look at: http://www.pnas.org/content/104/22/9364.long

David Kipling Atsuko's paper on field ID of A versus B Ciona is here: Sato A, Satoh N and Bishop J D D. Field identification of the ascidian species complex Ciona intestinalis in the region of sympatry. Marine Biology, 159 (2012): 1611-1619.

Message posted on NE Atlantic Tunicata on 20 May 2013
Animalia (Kingdom)
  Chordata (Phylum)
    Tunicata (Subphylum)
      Ascidiacea (Class)
        Phlebobranchia (Order)
          Ascidiidae (Family)
            Ascidia (Genus)
              Ascidia conchilega (Species)
Associated Species