About Annelid Worms

Annelid worms are distinguished by segmented body parts. Each segment has its own circular musculature. As the worm grows, additional segments appear. All species, except leeches, have hair-like projectiles that protrude from their cuticles. The projectiles help the worm burrow into the soil or other sediments. The epidermal layer of the worms also has a moist outer surface. More than 15,000 species exist around the world, and fall into three classes.

  1. Polychaetes Annelids

    • Predominately marine worms, the blood worm, ragworm, lugworm and tubeworm belong to the Polychaetes annelid class. Worms within the class have separate sexes. Polychaetes worms have soft projectiles on their segments that function as gills for some of the marine worm types. Most have up to 200 segments when fully mature. In the middle of the worm's body exist several segments that excrete a moist, lubricating substance. The worms within the class have a distinct head with noticeable eyes. They usually reside in the muddy bottoms of waterways or mud tubes.

    Hirudinea Annelids

    • The class Hirudinea contains leeches. As parasites, leeches spend their lives floating through water in search of mammals or fish to latch onto for a blood meal. Hermaphroditic, the worm has the capability of reproducing singularly because it contains both male and female reproductive organs. Most species carry their young on their bodies. Leeches have no head and boast 33 or 34 body segments. Leeches secrete an anticoagulant called "hirudi" which helps prevent the blood from clotting to prolong the leech's blood meal. Some leeches only require one to two blood meals per year to live.

    Oligochaetes Annelids

    • Earthworms belong to the Oligochaetes class of annelids and have the capability of asexual reproduction. The worms have the ability to multiply by breaking apart and regenerating a new body part or by laying eggs in small cocoons in the soil. Approximately 1 million worms can live in 1 acre of fertile soil, which they further improve by aerating it. Each worm in the Oligochaetes class shows no distinguishable head or eyes and has about 120 body segments. Both land and freshwater marine annelid worms exist with the Oligochaetes class.

    Benefits

    • Annelids feed on a diverse array of foods. Some eat decaying matter and others hunt small invertebrates. Feather-duster annelids feed only on planktonic organisms. Ragworms siphon the water through their mud tube home to find small, microscopic foods. Annelids have no skeletal system and have become a favored food for moles, some birds and hedgehogs. Microorganisms in the soil feed on earthworm castings. The earthworms' voracious feeding further breaks the substance down so plants can absorb its valuable nutrients.