what is nematodes

Nematodes, also known as roundworms or eelworms, are a diverse animal phylum that inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but there are many that are parasitic. Nematodes are very small, slender worms, typically about 5 to 100 µm thick, and 0.1 to 2.5 mm long. The smallest nematodes are microscopic, while free-living species can reach as much as 5 cm (2 in), and some parasitic species are larger still, reaching over 1 m (3 ft) in length. Nematodes are a major component of soil and sediment ecosystems, feeding on bacteria, fungi, or other microscopic creatures. They have been reported from every continent on earth and occur in deserts, swamps, the oceans, the tropics, and Antarctica. While most of the thousands of nematode species on Earth are not harmful, some cause diseases in humans and other animals or attack and feed on living plants.