Unusual life form filmed with sewer cam

YouTube link. 

It's a group of annelid worms, not a bryozoan, and it is definitely bizarre.

Update: Anonymous posted a thread from Metafilter with a suggestion that this is a viral promotional video. But a link there led me to another link at DeepSeaNews that had this comment from a bryozoologist:

Thanks for the video – I had not see it before. No, these are not bryozoans! They are clumps of annelid worms, almost certainly tubificids (Naididae, probably genus Tubifex). Normally these occur in soil and sediment, especially at the bottom and edges of polluted streams. In the photo they have apparently entered a pipeline somehow, and in the absence of soil they are coiling around each other. The contractions you see are the result of a single worm contracting and then stimulating all the others to do the same almost simultaneously, so it looks like a single big muscle contracting. Interesting video.

Second ipdate, from a reader of the blog:

This ID makes sense to me, especially after I reviewed the video again, because I've *seen* this behavior in clumps of tubifex worms. As a fishkeeper for about 20 years... my refrigerator was never without an open plastic bowl full of live tubifex worms, which make the greatest fish food ever. Since the bowl gave them nothing to hang onto, they would form a big clump wrapped around each other. And every time I opened the refrigerator door, the sudden light on the worms would cause the whole clump to contract, then slowly expand out again, just like we saw in the video. I now suspect that the movement featured in the video was caused by the camera light -- if you watch, you'll notice that it most often occurs immediately after the camera has shifted position.

One other explanation I read suggested that it is the heat from the light, not the light per se, that twiggers the propagating twitch.

(Reposted from 2009 to accompany an adjacent post).