Echiurans

Echiuran Worms

The proboscis of a bonellid echiuran moves over rocks collecting detritus and particulate matter to eat, while the body remains hidden in a burrow or hole in the rock. The arrows indicate the "Y" or "T" shaped end of the proboscis characteristic of these animals.  Photo courtesy of Rich Rosenbaum.

 

There are two major kinds of Echiuran worms.  One type, the Bonellid Echiurans, show up from time-to-time in live rock. These are small worms that live in burrows in the rocks or in crevices.  The green unsegmented body is baglike and remains hidden in the rocks.  They have a long proboscis which, as shown above, is "bifurcate," that is, split into two branches at the end.  All echiurans  are harmless sediment feeders, detritus feeders, or filter-feeding worms.  The major distinguishing characteristics are the lack of segmentation, and the way in which the introvert is split at the tip.

The second type of Echiuran, lives in a tube buried in sediments. These are the Echiurid Echiurans, and may be very abundant in many marine areas, but as they are buried out of sight, they remain unseen.  Unlike the bonellids, their proboscis is not bifurcate, and often looks rather like the business end of a spoon, and this gives them their common name of "spoon worms."  

The above eight images, courtesy of Andrew Trevor Jones show an echiurid in an aquarium.  Normally this animal would live in a tube and would pump water through the tube collecting food from the water with a mucus net made by the proboscis.  The proboscis is at the lower left end of the worm