I thought I was taking a picture of a flatworm.

When I was younger I allways loved turning over rocks at the creek looking for frogs and oher slimy critters. I guess I never outgrew the habbit.

On a dive last week I started flipping over sea-cucumbers (sand fish sounds much more exciting, the diving community should adopt that comon name) to see what was under them. Maby half of them had what I though were flat worms living on their under side. (never more than one per cucumber)

They moved very quickly and obviously did not appreciate being exposed to the light as as soon as you flip the cuke they quick move back into the shade. End result was the cucumber got to rolled around while I tryed to take the picture and keep the worm on the top side of the cucumber.(I hope the cucumber didnt get seasick)

Well when I got the picture on the computer it is clear that it is not a flatworm. So now I have no clue what it is.

Any Ideas?

Is it segmented - can't be sure from the photograph?

Also can you describe how it moved?

Ahaaah! Thanks Leslie!

So it's a Polynoid - a scale worm related to other Polychaetes. They sound really cool... Are those the elytra on its back??

Hey Leslie - do you know what they are doing under the holothurians??

Munching stuff I guess, but I thought scale worms were pretty active predators?

Wow, looks like some of them are bioluminescent! They'd be one crazy critter to see on a night dive with all those scales lit up!!

Oops, got so excited I forgot to mention it was a polychaete, in the family Polynoidae, otherwise known as scaleworms. Good on ya for filling in Anthony! the round structures are indeed the eytra (= scales). Some scaleworms are active predators but others are pretty lazy and many are commensal. I haven't a clue as to whether this guy is eating other critters that get stirred up as the cucumber moves around or swallows sand to digest the organics clinging to the grains. It could also feed on the cucumber's feces.

Thanks for the id Leslie. Gastrolepida clavigera So what is that. Some kind of worm I presume? PM or email me with your email address (if you dont want to post it here) and I'll email you the full resolution image if you want it. Or you can just download the above 900px version.

It could also feed on the cucumber's feces.

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Wow! what a job description. Where do I apply??

Here's a commensal scale worm common in California (it's a teaching shot, sorry). Arctonoe pulchra is often found between the shell & foot of the limpet Diodora aspera.

Wow! what a job description. Where do I apply??

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Just about anywhere, my friend!

Hey folks !

preparing to move to Panama, so mostly absent from the forum .. but trying to catch up whenever possible

one of my Russian colleagues did a study on this interesting polynoid

Gastrolepidia clavigera feeds on a variety of things, including epithelial tissue of sea cucumbers, and is so a parasite; however, it also feeds on parasitic copepods infesting sea cucumbers, and therefroe, is a mutualist, too .. it's quite complex in nature

see the following paper:

Britayev, T.A. & S Lyskin. 2002. Feeding of the symbiotic polychaete Gastrolepidia clavigera (Polynoidae) and its interactions with its hosts. Doklady Biologicheskikh Nauk, 385: 352-356.

cheerio

Art

Unbelievable, the amount of knowledge, here, in this little underwater digital photo forum. You guys are great!

Don