Hitchhiker ID Help

[jtma508]

So it's been pretty boring in the tank lately. I'm a little over a week into the cycle. Most of the tube worms have either died-off or are laying really low. Some bristle worms, lots and lots of pods and then this morning this guy showed up...

I tried finding him online but haven't seen anything close so far. I'd estimate his girth at 1/4 - 3/8 inch. It's hard to estimate his length since he's curled-up on himself. Maybe 3-4"?? I love his head-dress. Any ideas???

 

[jimroth]

Wow, that's a cool little guy you've got there. I'm going to take a guess and say it might be a medusa worm, a kind of sea cucumber. The tentacles look very cucmber-ish. Definitely an unusual hitchhiker!

 

[jtma508]

Doesn't look like any of the medusa worm pics I've turned-up. They seem to have more long antennae that are white. Nothing like this guy. I'm stumped. I figured it would be a quick google and an ah-hah.

 

[styndall]

Medusa worm is my only guess, too. Keep in mind that there are lots of species of medusa, and not all will be easily available in pictures on the internet.

Some description of the behavior might help. How does it move? What does it do with the feathery tentacles?

 

[jtma508]

So it gets weirder. I noticed that it had a strange soikey thingy on its tail end:

While I watched it expelled that thingy which drifted off into the tank. Doesn't look like poop. Offspring perhaps?

Here's another pic of the critter:

 

[jtma508]

Just wanted to bump this sucker until we get an ID.

 

[B.C.theReefer]

When in doubt, get it out. Could be harmless or it could be a killer. Just my opinion.

 

[kar93]

Banish it to the sump until you get a positive ID.

 

[jtma508]

BUMP

 

[Paintbug]

i believe that is going to be some type of Terebellidae sp. PM LeslieH to make sure. if any one here would know, she would.

 

[LeslieH]

Paintbug's right (very good, Grasshopper!) - it's a terebellid polychaete. Normally it would be in a tube either in a crevice in the rock or running under it. it's not happy - that's why it's out in the open. I can't identify it to genus and species unless I know the region where the rock came from and I have the worm in front of me under a microscope. Terebellids feed by extending their long tentacles over the substrate & carrying back appropriately sized particles to their mouths. they get the sand & other components that make up their tubes the same way. the prominent red feathery things are gills used for respiration.

Now the really interesting thing is the odd spikey thing at the end which drifted off. I believe that's a parasitic copepod which decided it was time to take a hike. Some copepods are internal parasites only when they are juveniles; just before or after transforming into the adult stage they move out of the host & into the water. Other copepods do it the reverse way, and yet still others are parasites during their entire life cycle. It's possible the worm has more parasites inside it.