Spoon Worms - Echiura

Characteristics:

Many echiurans live in crevices or buried in sand or mud. Occasionally the elongated, sheet-like mouth (proboscis) can be seen stretched out on the bottom. It is not unusual that the mouth is longer than the rest of the body. A digestive channel runs in full body length to the posterior end. The spoon worms absorb oxygen through the skin. They usually feed on deposits on the seabed.

In many cases, you will only encounter the females, as the males are of microscopic size and live inside the females. Larvae touching the skin of an adult female turn into males. For some echiurans the male has never been found.

Taxonomy:

The Echiura or spoon worms is a small phylum, including only 170, exclusively marine, species. Recent DNA-studies suggest that they should be considered a subgroup of Annelida, even if they do not show any sign of body segments, which is regarded as a typical feature of annelids. The free-swimming larval stages of annelids and echiurans are very similar. There are only a single class and two orders of spoon worms, Bonelliida and Echiurida.