Phylum: Annelida

Segmented Worms

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Scaleworms near a seafloor volcanic vent.

Segmented worms have a digestive tract with two openings, and a segmented body, often with appendages. There are internal walls separating the segments, and membranes bind the internal organs in place. There are three main classes of annelids: Polychaeta, oligochaeta, and hirudinea.

Class: Polychaeta

Polychaetes are marine annelids with a pair of bristly, fleshy appendages on each segment. Often there are also appendages or a plume at the mouth end. Many live in tubes. Some examples are tubeworms, plumeworms, and fanworms.

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Class: Oligochaeta

Oligochaetes lack appendages and have few bristles. They can be either terrestrial, or aquatic. The earthworm is a member of this class.

Giant Earthworm. Alen Yen, Environment Autstralia, Australian Nature Conservancy.

Class: Hirudinea

The members of this class are the leeches. Leeches lack appendages, and most live in fresh water. Leeches are either carnivores or blood-sucking external parasites.

Leech. Dr. D.L. Gustafson

Marine Leech. A.E. Migotto