Nematodes (round worms)

They have very characteristic S-shaped bodies and are often very active. The body is cylindrical and the skin (cuticle) is tough and only slightly flexible. Nematodes inhabit all possible environments. They can not only be found in the soil but many species are aquatic or live as parasites in other organisms. They form an important role in the breakdown of organic matter in soil and the bottom of ponds.

Soil is an excellent habitat for nematodes, and a thimble full of soil may contain several thousand of them. Because of their importance to agriculture, much more is known about plant-parasitic nematodes than about the other kinds of nematodes which are present in soil. Most kinds of soil nematodes do not parasitize plants, but are beneficial in the decomposition of organic matter. These nematodes are often referred to as free-living nematodes.

Some soil fungi are predators that trap and consume tiny living organisms such as soil roundworms. The prey is trapped by sticky filaments, like spider webs, and by circular ring snares that constrict around whatever touches them. All this takes place on a microscopic scale we can’t see. These predators are the mycorrhiza symbionts of plants.

hypha strangling a snared roundworm