Characteristics:
The annelids are called segmented worms because of the elongated bodies, divided in multiple segments. Primitive species consist mainly of identical segments while others have a set of more specialized segments. The segmented worms come in a huge variety of shapes and colors. Many of the worms live their lives buried in the sand while others stand up like flowers. Some are microscopic in size, others can reach a length of 3 metres.
Taxonomy:
The are more than 17000 different species of segmented worms existing today. Marine species are members of one of two classes,
Polychaeta (Polychaete worms) or
Hirudinea (leeches). The third class,
Oligochaeta, includes the well-known earthworms. The phylum is up for a revision as recent research has revealed that the leeches should probably join the oligochaetes, together with the earthworms. The oligochaetes is about to be regarded a subgroup of the polychaetes, together with
Echiura which is currently regarded as a separate phylum. Perhaps all annelids will end up as polychaetes, in the end. Hopefully, genetic studies will end the confusion.
