Question About Segmented Worm Behavior

My wife and I were diving in Bonaire in January and we kept finding these spider web looking structures in coral heads. They were quite common as we saw them on almost every dive both day and night. The web seems very strong and must be somewhat sticky as I saw a squat anemone shrimp stuck in one.

The Things Web by Bud Barr, on Flickr

The Things Web1 by Bud Barr, on Flickr

After what seemed like endless searching, we finally got a look at what is down there.

The Thing by Bud Barr, on Flickr

The Thing2 by Bud Barr, on Flickr

The Thing5 by Bud Barr, on Flickr

The Thing12 by Bud Barr, on Flickr

The Thing14 by Bud Barr, on Flickr

Over 3 weeks, we saw a creature in 5 separate webs all during the day. The ones I took pictures of did not seem to be bothered by our flashlights or my strobes. One of them, after about 10 minutes of observation, backed down the web a little ways and then turned head down and went deeper into the coral head. We watched it's segmented body go by for what seemed like forever so it was quite long. Soon after, it's head came part way up through a different web in the same coral head.

We are guessing "The Thing", but we haven't seen this web building behavior documented anywhere so I thought someone out there might be able to shed some light on it.

Thanks,

Bud

Hi Bud --

What a great set of photos! You're right - it's an eunicid polychaete although whether or not it's "The Thing" I can't say from the photos. I suspect that name is getting to be the common name for any large eunicid found in the Caribbean. The web is just the anterior part of an extensive tube or burrow lining made with solidified mucus which is secreted from special glands along the body. One study of coral reef eunicids concluded that they were responsible for a large part of the reef's structure due to their habit of moving & cementing chunks of coral rubble into place. What I find especially interesting in your remarks is the suggestion that they also use the outermost portion of the tube to catch food.

This page by Ria Tan has a good discussion of different types of tubes built by polychaetes on a reef flat in Singapore:

http://www.wildsingapore.com/wildfacts/wor...m/tubeworms.htm

Thanks for posting--

Thanks Leslie!