Found critter on arm of Featherstar

Very small and fairly quick too. As I approached the little critter would move onto the other side of the arm to avoid me.

Looks like a flatworm.

Marli

It has little legs though...?

Which makes it a myzostome. These are ectocommensals and parasites which live primarily on crinoids and on other echinoderms. There's been a lot of work done on the systematic placement of the family Myzostomidae, much of it contradictory. Right now it's back among the Polychaeta.

http://19thcenturyscience.org/HMSC/HMSC-Re...27/htm/doc.html

http://webs.lander.edu/rsfox/invertebrates/myzostoma.html

I read the info you linked Leslie and am amazed that the Polychaeta group is so large. Is it becoming a dumping ground for random critters which defy classification or are there really over 8000 Polychaetes that are so well related?

Oh, also, does this mean I found a worm for you?!

Yes, you did, and an unusual one as well!

8000 is probably a low number. In recent years several other groups have been placed into Polychaeta based on larval development, morphology, or DNA. There are also many many undescribed species out there, overlooked because they're so small or well hidden.

Isn't this too big for a myzostome?

Cheers,

Paddy

Not at all. They get up to a couple of centimeters. What's more unusual is that it's fairly conspicuous against the crinoid. Most of them are well camouflaged by means of matching color, adhering tightly to the crinoid's arm or body, or being hidden inside a cavity. This one - http://wetpixel.com/forums/index.php?showt...mp;hl=myzostome - is more typical.