How many species of Annelida are there today?

There are approximately 15,000 known species of Annelida, a phylum that includes segmented worms such as earthworms, leeches, and marine polychaetes. This number may vary as new species are discovered and taxonomic revisions occur. Annelids are classified into three main groups: Polychaeta, Oligochaeta, and Hirudinea. Overall, they play vital roles in ecosystems, particularly in soil health and marine environments.