Worm-like animals
How to tell them apart?
updated Apr 2020

Several small wriggly animals look like worms, with long smooth bodies.

Peanut worms are unsegmented worms that burrow in the ground. Synaptid sea cucumbers have bumpy soft bodies and are usually draped on sponges or ascidians. The worm eel is a fish that burrows in the ground or hides in crevices among coral rubble.
They don't move very quickly, but are not as slow as synaptid sea cucumbers. They generally don't move much or do so quite slowly. A very active and fast moving animal.
Generally do not have tentacles around the mouth, nor eyes. They have a ring of tentacles around the mouth that gathers edible bits from the water. They have no eyes. It has small eyes and a mouth.
Peanut worms belong to Phylum Sipuncula which is different from the more commonly encountered segmented worms of the Phylum Annelida. Synaptid sea cucumbers belong to Phylum Echinodermata, Class Holothuroidea which includes other sea cucumbers. The worm eel is a fish and thus a vertebrate (like us) belonging to the Phylum Chordata.

More comparisons

The long smooth ribbon worm
can retract quickly.

Long black sea cucumbers
are large and worm-like too.

Big synaptid sea cucumbers
are large and worm-like too.

The Yellow-lipped sea snake is fast
moving and covered with scales.

Eels can be thick, long
and snake-like.

The arms of hidden octopus may
sometimes be mistaken for a worm.

how to tell apart
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