andrewcowley's picture

Didemnid Ascidian - was Pale orange sponge

Observed: 30th August 2011 By: andrewcowleyandrewcowley’s reputation in Invertebratesandrewcowley’s reputation in Invertebrates
sponge-03-001 1
sponge-03-001 1 2

A thin - 1-2 mm, encrusting sponge, found at ELWST in the holdfast of Laminaria digitata and near Morchellium argus. Has a 'chamois leather' texture.
New photos added. Preliminary ID.

Species interactions

No interactions present.


andrewcowley's picture

apology for micrograph banding

That seems to be what happens if you power the light source from a cheapo inverter.

Joe Botting's picture


You're going to struggle with this one. My guess is a Hymeniacodon species, and some have relatively few robust spicules (although normally abundant smaller ones). Did you sample the expected size range for microscleres or could they just have slipped through?

I don't think it's one of the aspicular groups like the oscarellids.

andrewcowley's picture


Thanks Joe

Microscleres were less than 1μ if they existed. Couldn't see any at 600X with a good Leitz scope.

I agree it doesn't look (or feel) like an Oscarellid.

I'll repeat the experiment next week if possible. Is there anything else (short of DNA sequencing ;-) that can be used to identify it?

I prepared the spicules with household bleach, washed in tap water and viewed in water. I presumed that water had as good a refractive index contrast as any easily available mountant. Any changes I should make?

Joe Botting's picture

The only change I can think

The only change I can think of would be to use ethanol to view the spicules through (possibly a thin layer of it, dyed with food colouring) - but I must add that I've rarely looked that closely at modern sponges, as mine tend to have been dead for 450,000,000 years or so. :-)

The only other thing I can think of is to try Clare Valentine at the NHM - if anyone in the UK is likley to be able to get a definitive ID on this, it's her.

andrewcowley's picture

More images

New photos at greater magnification. I now think this may be a didemnid ascidean but I can't match it to a species in Hayward and Ryland, Vol 2. It seems close to Didemnum fulgens or Polysyncraton bilobatum.

dejayM's picture

Andrew's Website

Just to say that if anyone tries to access Andrew's Website - the link above - then this will clinch it

dejayM's picture

Sponge vs Ascidian

Unfortunately that link now also fails. We hope that one day Andrew's website will return.
I came searching for historical references to Laimaria.
Andrew's change of heart here, regarding the ID can be supported by picture 2 only. Surely that is an ascidian but the other two pictures show sponges.
Notwithstanding I have now agreed to the second ID and this has shifted Likely.