Nematodes are the class of animals belonging to the phyla Aschelminthes. Their cross-section is round in shape and hence called roundworms. They have features similar to tapeworm but, have some distinct characters like
- Body systems
- Reproduction type
- Food habits
Size: Nematodes can be microscopic but even large and visible to the naked eye. Their size ranges from 0.3mm to up to 8 meters in length.
Body systems: Nematodes have somebody systems like digestive, nervous, reproductive, excretory systems sufficiently developed.
Reproduction type: Many nematode species have separate male and female animals. This is called dioecious nature. While some of the species have both male and female systems and act as hermaphrodites.
The reproduction is by sexual means and males copulate with female organisms through a copulating projection called a spicule.
Food habits: Nematodes have diverse food habits. Some of them are free-living and eat algae, fungi, excreta, and other organic material. These free-living nematodes act as natural decomposers and help in the recycling of nutrients into the environment they live in.
Also, there are many nematodes that act as parasites. They live as parasites on both animals and plants.
Some of them are very troubling to humans as they cause diseases in humans by an infestation. Some popular ones infecting humans include Ascaris, trichuriasis infesting the intestine of humans. Both these parasites derive nutrition from the human digestive system. They just absorb the digested nutrients without the need for further digestion in their body. Due to this, the infected person is undernourished and develops related symptoms.
Besides, there is filariasis which blocks lymph veins and causes elephantiasis.
Distribution: These animals are widely distributed all over the earth. They can be found in soil, freshwater, marine water, deserts, etc.
Uses of nematodes: Although these are responsible for few diseases in humans, they can still be used as
1) biopesticides in agriculture.
2) Role in the nitrogen cycle.
3) They control the bacterial population in the soil.