Polychaetes - (‘poly’ = many, ‘chaeta’ = bristle) worms

What do they DO?

Like all animals, polychaetes must breathe, eat, find (or make) shelter, and reproduce.  Polychaetes solve all these life problems in an amazing variety of ways.  Some hunt other animals using antennae to ‘sniff’ the water and seabed.  They use palps to feel out the prey right before their jaws shoot out of their mouths and capture their dinner with multiple sets of jaws.  Others may graze algae along the surface of rocks, filter plankton out of the water currents, or swallow enormous quantities of sediment just to digest out the thin bacterial film coating each sand grain.  

Many polychaetes burrow into the ocean floor for protection.  While doing this they also return buried nutrients to the surface, oxygenate the sediments (just like earthworms in your garden), and may bind sand grains together with mucous.  Others build tough tubes out of limestone or cement bits of rock and shell to themselves for armour. 

In terms of reproduction, polychaetes offer a dizzying array of methods.  Most polychaetes are dioecious (have separate males and females), but some are hermaphrodites.  Some shed eggs and sperm into the water and hope they got lucky, others go through elaborate courtship rituals, building special structures for the purpose.  Some even sprout a bunch of babies from their bodies which drop off and grow into new worms!  Many worm parents never see their young while most species make special cocoons or otherwise tend the eggs, and protect the little ones until they’re big enough to leave on their own.