Nematodes consume a variety of different materials, including plants, fungi, algae, bacteria and other nematodes. As with other organisms, some nematodes are herbivores and consume only plant and vegetable matter, while others are carnivores and rely on meat for their dietary nutrients. Nematodes live in many different environments, which explains the diverse array of items that they consume.
Nematodes vary in size and shape, but are all classified as non-segmented worms. Most live in dirt and soils, but a few live in oceans and other aquatic environments. Nematodes have distinct biological and physical differences, which allows scientists and researchers to classify and distinguish them. These organisms, however, are also classified into groups depending on their diets. Nematodes occupy different trophic levels on the soil food web. Nematodes belonging to the first trophic level feed primarily on plants and algae. Those in the second trophic level are considered grazers. These organisms feed primarily on bacteria and fungi; they may consume small seeds and plant spores as well when primary food sources run low. Third-level, or predatory, nematodes consumer other nematodes and a variety of protozoa. They are parasitic in nature, and may eat smaller organisms whole or attach themselves to the bodies of larger nematodes, where they slowly consume prey from the outside in.