Worms

Worms is a common name for several groups of elongated, soft-bodied animals that lack limbs as adults. They are not a single scientific group, but rather a collection of organisms from several different phyla that share a worm-like, orderless body plan. Most live in moist environments, including soil, freshwater, and marine habitats, and range from microscopic to several meters in length.

The largest and most familiar worm groups are flatworms (Platyhelminthes), segmented worms (Annelida), and roundworms (Nematoda). Flatworms have a simple, often ribbon-like body with a basic digestive system or none at all. Annelids include earthworms, leeches, and marine polychaetes, characterized by segmented bodies and a true body cavity. Nematodes, or roundworms, are usually slender and cylindric, with a flexible outer covering and a pseudocoelom; they include many free-living species as well as important parasites.

Anatomy and development vary widely. Flatworms tend to have simple organ systems; annelids display pronounced segmentation and more complex organs; nematodes are typically unsegmented and highly adaptable. Reproduction can be sexual or asexual, and life cycles may involve direct development or multiple larval stages. Some species are hermaphroditic, while others have separate sexes.

Ecologically, worms play crucial roles. Earthworms aerate and mix soil, aiding decomposition and nutrient cycling. Marine and freshwater worms contribute to sediment structure and food webs. Parasitic worms, including tapeworms and roundworms, affect humans, livestock, and crops, making understanding their biology important for health and agriculture. Vermiculture and soil restoration practices exploit beneficial worm activity to improve ecosystem services.