Creatures Called Worms

Posted by John Blatchford May 14, 2009

Annelids are the ‘True Worms’, and most are long thin and wiggly and the nematodes (or ‘Round Worms’) look similar. Many other phyla share this body shape and are called ‘worms’ of one type or another.

• Flatworms are mostly parasitic, and as the name suggests are typically flat rather than round. Horsehair Worms are also parasites, as are the Spiny-headed Worms, and these two phyla are capable of modifying their host’s behaviour (see ‘Horsehair Snakes’ ) – sometimes called ‘brain jacking’.

• Most ‘Arrow Worms’ are active predators in the plankton, swimming efficiently and capturing small animals with their hunting spines that act like teeth, and most ‘Ribbonworms’ hunt on the sea bed.

• All the other ‘worms’ (jaw worms, acorn worms, horseshoe worms, rude worms, and peanut worms) either scrape food or filter feed.

There are hundreds of thousands of species of animals called ‘worms’, but all the different phyla have in common is the body shape. With the exception of the earthworms (annelids that most people will have seen) these phyla are unfamiliar to all but specialists, and the details of their evolutionary relationships with one-another are not at all clear. Their soft bodies rarely leave fossil evidence, and it will be necessary to study molecular details (DNA in particular) to clarify these matters.