Nematode

Nematodes or roundworms belong to the phylum Nematoda. They are a diverse animal phylum inhabiting a broad range of environments. Nematode species can be difficult to distinguish, and although over 25,000 have been described, of which more than half are parasitic, the total number of nematode species has been estimated to be about 1 million.

Anatomy

Nematodes are 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, and some parasitic species are larger still, reaching over a meter in length.

Life cycle

Nematodes follow an eutely pattern of development. The young nematode hatches from an egg. Most nematode species are dioecious, with separate male and female individuals, though some, such as Caenorhabditis elegans, are hermaphroditic.

Ecology

Nematodes play crucial roles in the soil ecosystem. They are ubiquitous in marine, freshwater and terrestrial environments, where they often outnumber other animals in both individual and species counts.

Parasitism

Many nematodes are parasitic, living inside the bodies of animals or plants. The parasitic nematodes include roundworms, hookworms, and pinworms.

Research

The nematode Caenorhabditis elegans is one of the most important model organisms in modern biomedical research.

See also

• Helminthiasis
• Nematode infection
• Nematode morphology

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