Nematode
Say it: NEM-uh-tohd
A nematode, or roundworm, is an unsegmented worm with a round body and a tough cuticle, from a vast phylum of free-living and parasitic species.
Also: roundworm, nematodes
Definition
What is a nematode?
A nematode is any member of the phylum Nematoda, the roundworms. Nematodes are slender, unsegmented and usually tapered at both ends, and they are round in cross-section, unlike flat tapeworms and flukes. A tough, flexible cuticle covers the body and is shed several times as the worm grows, which places nematodes with arthropods among the molting animals, the Ecdysozoa. They have a complete gut with a mouth and an anus, and a fluid-filled body cavity called a pseudocoelom that works as a hydrostatic skeleton. Tens of thousands of species have been named, living almost everywhere, from soil and seabed to the insides of plants and animals.
Most are free-living, but many are parasites. Soil-transmitted species infect more than a billion people where sanitation is poor: the large roundworm Ascaris lumbricoides, the whipworm and the hookworms, which feed on blood and cause anemia. Others include the pinworm, Trichinella from undercooked meat, filarial worms spread by insects, which cause river blindness and elephantiasis, and many crop pests. Drugs such as albendazole and ivermectin are widely used against them.
The tiny free-living Caenorhabditis elegans, about a millimeter long, is a major model organism; work on it revealed key genes of programmed cell death and the process of RNA interference.
Word parts
Where does the word “nematode” come from?
- nemat-
- threadGreek nema, nematos
- -ode
- like, in the form ofGreek -oeides
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Related
Terms that go with it
- HelminthA helminth is a parasitic worm, such as a roundworm, tapeworm or fluke, that lives in a host and is usually visible to the eye as an adult.
- ParasiteA parasite is a living thing that makes its home on or inside a host organism and feeds from it, usually causing the host harm.
- InvertebrateAn invertebrate is any animal without a backbone, a broad grouping that includes insects, worms, mollusks, jellyfish and most animal species.
- ExoskeletonAn exoskeleton is a hard external skeleton that supports and protects an animal's body, as in insects, spiders and crustaceans.
- PhylumA phylum is a major rank in biological classification, below kingdom and above class, grouping organisms that share a basic body plan.
- RNA interferenceRNA interference is a natural process in which small RNA molecules guide the destruction or blocking of matching messenger RNAs, silencing specific genes.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 28.5 Superphylum Ecdysozoa: Nematodes and Tardigrades
- WHO: Soil-transmitted helminth infections fact sheet
- OpenStax Microbiology, 5.2 Parasitic Helminths
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