A tube worm is a worm-like sessile invertebrate that anchors its tail to an underwater surface and secretes around its body a mineral tube, into which it can withdraw its entire body.
The tube worm does not have many predators but if threatened, their "plume" may be retracted into the worm's protective tube. This plume provides essential nutrients to bacteria living inside a specialized organ within its body as part of a symbiotic relationship.