Tube-dwelling worm, not a 'duster'

[ptychoptera]

http://reefcentral.com/gallery/data/500/165045IMG_3679.jpg
...not a very good photo, but one of the white tentacles is visible.

I collected numerous specimens of this species in some rather filthy coarse sand/crushed coral. I haven't gotten much of a glimpse of the worms that make these, just a couple of opaque to translucent whitish tentacles that periodically extend from the opening of it's tube.

The tube itself seems perhaps 2mm in diameter and composed of a parchmentlike material (chitinous?). Covering this material are grains of sand/gravel that are a few millimeters in size. The tubes seem to vary, with some extending straight up and others bent in an L shape, with part of the tube resting on the upper surface of the sand. Length of the visible tube is around an inch. During collection I observed that they seemed somewhat colonial, but have yet to see this in my tank. They also seem to abandon tubes somewhat regularly, as I've yet to see a tube exist for more than a day.

Any ideas Leslie?

[LeslieH]

The tube-dwelling polychaetes with two palps most commonly found in tanks belong to either family Chaetopteridae or Spionidae. Yours is probably a chaetopterid based on the fact you observed a "parchment" tube. That's exactly the word we use for their tubes. It's solidified mucus. In both families the animals feed by collecting detritus with the palps which are grooved & lined with cilia; the food travels down the groove to the mouth.

If you really want to be sure of the type you'll need to get the animal out of the tube. Try to get the entire tube - parts of it might be under a rock, in a crevice, or in the sand. If the animal is in it the tube will move when touched Use your forceps to gently press down on one end of the tube & slowly move the forceps towards the other end. With enough patience you can get the worm to crawl out of its tube & take a photograph. Have fun!