What are nematodes: characteristics, classification and examples

Commonly known as roundworms , nematodes are one of the great taxonomic phyla in which invertebrates of the Animal or Animalia kingdom are classified .

Generally, nematodes are known for their ability to infect and cause diseases, both in plants and animals, being responsible for the loss of crops and ornamental plants, as well as infectious gastrointestinal diseases in humans and other animals (mammals and fish, mainly). In this way, nematodes are considered one of the most widespread phytopathogens and parasites in any corner of the planet.

Among the main characteristics of nematodes are:

• They live both freely in arid and moist soils, in fresh and salt water habitats, as well as parasitizing plants and animals on which they feed.
• Its size is very varied, from a few millimeters to more than half a meter.
• Its body is round and elongated, cylindrical in shape and without segments. Its symmetry is bilateral.
• The mouth of nematodes has different structures that allow them to attach to tissues and obtain food, such as teeth, plates and even mouth hooks.
• The outer surface of adult nematodes is very resistant, they have a cuticle and several muscular layers.
• Regarding their diet, nematodes have developed different strategies, such as: aspiration for ingestion of blood, absorption of destroyed tissues, as well as intestinal content and nutrients present in different body fluids (in animals) or sap ( in plants).
• Nematode reproduction can be both sexual and asexual, through parthenogenesis, fragmentation or embryogenesis. Depending on the environmental and survival conditions in which the adults find themselves, they will choose one reproductive method over another.

The phylum of nematodes includes about 25,000 species . These invertebrate animals have evolved throughout their biological history in order to adapt to new hosts to parasitize, both within the kingdoms of animals and plants. For the classification of nematodes , the most widely used classical method is based on morphological criteria, which allow distinguishing within the nematode phylum, the following classes and subclasses:

Clase Adenophorea

• Enoplios (subclase Enoplia)
• Chromadoria (subclass Chromadoria)

class

• Rhabditids (subclass Rhabditia)
• Senephrenics (Spiruria subclass)
• Diplogasterios (subclase Diplogasterida)

In the next section, we will learn more about the world of nematodes with concrete examples of common species.

Here is a list of examples of nematode species , both species and genera that are commonly known in many cases for the disease or symptoms they cause:

Examples of Parasitic Nematodes in Animals

• Intestinal earthworm ( Ascaris lumbricoides )
• Hookworm nematode (genus Ancylostoma )
• Whipworm or whipworm ( Trichuris trichiura )
• Anchylostomiasis nematode (Ancylostoma duodenale)
• Necátor americano (Necator americanus)
• Strongyloidiasis nematode ( Strongyloides stercoralis )
• Guinea worm ( Dracunculus medinensis )
• Anisakiasis nematode (genus Anisaki )
• Oxiuros (Enterobius vermicularis)
• Triquinas (Trichinella spiralis)
• Filariasis nematode (order Spirurida)
  

Examples of plant parasitic nematodes

• Potato root nematode (genus Globodera)
• Migratory ectoparasitic nematode (genus Xiphinema)
• Gall-inducing nematodes (genus Meloidogyne)
• Cystic nematodes ( Heterodera fici )
• Spiral nematode (genus Helicotylenchus)
• Root knot nematode (genus Meloidogyne)
• Radical lesion nematode (genus Pratylenchus)
• Drilling nematode ( Radopholus similis )
• Leaf nematode (genus Aphelenchoides)
• Rot nematode ( Ditylenchus destructor )
• Stem and bulb nematode ( Ditylenchus dipsaci )

Below you can see images of some of these examples of nematodes.

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