Nematodes are considered a group of worms, and they occur naturally. The worms are hard to detect visually. They can also be called common soil pests as they affect plants. They live in the soil at low levels and can enter the farm through infected transplants. They are the parasites of plants and animals and can also attack insects.

What is Nematoda?

Nematodes are commonly known as roundworms, and they are unsegmented vermiform pests. They are called parasites of insects, animals, and plants. They can enter the farm through infected plants and cause severe damage to the plants. The most important factor is that all the nematodes are not harmful; some of them are essential for nutrient recycling.

Figure 1: Nematoda

Nematoda is mostly called a free-living organism and can enter plants to extract nutrients from the root cell. They are called the stress tolerance of plants and sometimes play an important role. Plants having abundant water and nutrients can tolerate nematode attacks. Once worms enter the soil, it is impossible to eliminate them.

The name nematodes came from the word Nematoidea. It includes some characteristics and has been classified into different matters. The presence of nematodes in the soil can feed on fungi, bacteria, and other nematodes. They have a significant role in nutrient recycling but also cause diseases like Trichuriasis, Ascariasis, Hookworm, and Filariasis.

Characteristics of Nematoda

Some of the important characteristics of Nematoda are as follows:

  • They are cylindrical.

  • They consist of a body that is bilaterally symmetrical and triploblastic.

  • The worms are sexually dimorphic.

  • Nematoda contains a cavity or pseudocoelom.

  • The group of worms is free-living or parasitic.

  • They exhibit tissue-level organization.

  • It poses the characteristic that says the alimentary canal is distinct, with the mouth and the anus.

Nematoda contains some features that say it has an internal fertilization and reproduction process, which is sexual. These worms have amoeboid sperm cells, and they have longitudinal body-wall muscles. Their chemosensory organs are called aphids and are situated on the lips. They have cuticles which moult periodically.

Classification of Nematoda

Nematoda is divided into two parts, and they are:

  • Phasmidia or Secernentea

  • Aphasmidia or Adenophorea

Phasmidia or Secernentea are mostly parasitic, and their caudal glands are absent. They contain unicellular, pouch-like sense organs called plasmids which are an important part. It is seen that the excretory systems have paired lateral canals and examples are Ascaris and Enterobius.

Figure 2: Ascaris

The class Phasmidia is divided into the following orders:

  • Rhabditida males have copulatory spicules and a posterior lobe at the pharynx.

  • Strongylida is vertebrate parasites devoid of lips and have a well-developed buccal capsule.

  • Oxyurida is small or moderate in size, and they can be invertebrates or vertebrates.

  • Ascaridida is an oviparous, large stout nematode living as a parasite in the intestine of vertebrates.

  • Spirurida is the thread-like organisms that vary in size from moderate to large.

  • Trichuroida possesses a slender pharynx, and the mouth is devoid of lips.

  • Camallanida males have no bursa, and they are oviparous thread-like organisms.

Aphasmidia or Adenophorea are free-living organisms whose excretory system has no lateral canals. They contain caudal glands, but they have no Phasmids, and its examples are Some examples of this factor are Capillaria and Trichinella

The class Aphasmidia or Adenophorea is divided into the following:

  • Enoplida is mostly marine, and the cuticle contains bristles.

  • Dorylaimida is mostly terrestrial, and it consists of 6-10 labial papillae.

  • Mermithida, in the larval stage, lives as parasites, whereas in the adult stage, they are free-living.

  • Chromedorida contains a posterior bulb at the pharynx, and the cuticle is devoid of bristles.

  • Desmoscolecida contains ringed cuticles with prominent bristles, and they are marine or free-living.

  • Monohysterida has circular amphids and can be terrestrial, freshwater, and marine.

  • Araeolaimida contains labial papillae, and the cuticle is smooth.


Nematoda is also known as roundworms, and there are mainly 15,000 species of Nematoda present in the world. They are the parasite of animals, plants, and insects, and they harm the plants. They enter farms, infect the plants, and damage plants. It plays an important part that it plays an important role in nutrient recycling. They are also called unsegmented vermiform pests and are free-living organisms.


Q1. What animals eat Nematoda?

Ans. It is seen that nematodes can fall prey to other nematodes and insects. The insects are like diplurans and beetle, fly larvae and fall prey on centipedes, tardigrades, mites, and symphylans.

Q2. How does Nematoda help in soil processes?

Ans. Nematoda has an important role in distributing bacteria and fungi through the soil. They also process through the roots by driving live and dormant microbes on the surface and in the digestive system. It also helps maintain the nitrogen process of soil and helps in nutrient recycling.

Q3. Is the entire Nematodes parasite?

Ans. It is seen that 40% of the nematodes are free-living, and they usually feed on protozoa, bacteria, and fungi. The other 40% of the nematodes are parasites, most of which are parasites to animals. The nematodes can also be found in soil and plants.

Q4. What are the classes of Nematoda?

Ans. It is seen that there are around 15000 species of Nematoda in the world. Some live in the root of plants, and some live inside the plants. There are two main classes of Nematoda: Phasmidia or Secernentea and Aphasmidia or Adenophorea.