Why would bristle worms swallow sand?

[desertreefer]

Dr. Ron,

I examined three small bristle worms under my steromicroscope recently and I am a bit puzzled. Two of the worms appeared to have rather large sand grain in the posterior end of their bodies. One of the worms had three large chunks (large compared to the worm) that looked like they would have been too big to swallow, much less pass out of the anus. Do they swallow sand grains? If so, why?

 

[rshimek]

Hi Sandy,

They definitely eat sediment. They digest the bacteria and other micro-organisms off the sediment grains. So... really they are not "eating" the sediment, but rather the bacterial frosting growing on it.

In our systems this is a way of recycling habitat to keep the bacteria bed healthy and growing.

 

[desertreefer]

Dr. Ron,

These guys should consider smaller particles. They must have resembled snakes swallowing eggs trying to get these down. The worm with the three large chunks in his gut was having difficulty moving!