Annelids, members of the phylum Annelida, are a large phylum of invertebrate animals. The species exist in and have adapted to various ecologies, including underwater and in moist terrestrial environments. Although many species can reproduce asexually and use similar mechanisms to regenerate after severe injury, sexual reproduction is the normal method in species whose reproduction has been studied.

Annelids are bilaterally symmetrical, serpentine, segmented invertebrate organisms. Each segment has the same sets of organs and most have a pair of parapodia, or small bristles, to move. Walls often separate the segments of many species, but are poorly defined or absent in others. One of the most well known annelids is the earthworm species of worm; they are an important supporter to the terrestial food chain as prey, and like other annelids they also enrich the soil they live in thanks to their burial. Marine annelids in particular end up allowing oxygen to penetrate the seafloor, stimulating ecosystem development.

Species

• leech
• worm
• earthworm