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Nematodes - Shanmugam IAS academy in coimbatore


What’s in news?

The global analysis of nematodes, a study reveals that, a pinch of soil could get over a hundred soil worms or nematodes.

Key data’s:

  • This is the first global analysis of nematodes which consists of a team of over 50 researchers and the study published in the journal “Nature”.
  • The researchers done only on the top 15 cm of soil and collected over 6,500 soil samples from all seven continents of the world and found that there are about 57 billion nematodes for every human being on Earth.
  • Their total biomass of the collected sample comes to around 300 million tonnes which is about 80% of the combined weight of Earth’s humans.
  • Sub-Arctic regions have the highest abundance (38%) of nematodes followed by the temperate regions and by tropical region.

Why worms prefer colder region?

  • Soil organic matter content was the key driver for nematode abundance.
  • The low temperature and high moisture in the sub-Arctic regions reduce the decomposition rate of organic matter.
  • This leads to accumulation of organic matter and the nematodes happily thrive on them. 

Research and findings on Indian Soils:

  • The soil samples were collected from Western and Eastern Ghats and the Himalayas of India.
  • Since the 1992 Earth summit, the Environment Ministry has given more emphasis to the ‘above ground biodiversity’, than the ‘below ground biodiversity’.
  • These nematodes play a crucial role in the environment as they are responsible for production of about 19% of ammonia of the soil. They are also important bioindicators of soil ecosystem health.
  • Various kinds of bacteria, fungi, arthropods and a wide variety of nematodes inhabit the soil


  • Nematodes are worm shaped, nearly microscopic animals, many of which are virtually invisible to the unaided eye when they are in the soil or within plant material.
  • These are roundworms and their size can vary from a tiny 0.2 millimetre to a few metres.
  • They are responsible for “around 2.2% of the total carbon emission from soils.
  • Of the known nematode species, approximately 50%, 25%, 15%, and 10% are
    • Free-living nematode – 50% – Very important in maintaining the soil bio-dynamic system, especially in soil with low organic matter content
    • Marine nematode – 25%
    • Animal parasites – 15%.
    • Plant parasitic nematodes (PPNs) – 10% – Feed on plants and reduce crop growth and yield efficiency
  • The nematodes play a crucial role in the environment as they are responsible for production of ammonia of the soil and also a bioindicator of soil ecosystem’s health.
  • Nematode Metabolites may also stimulate specific bacterial growth by releasing growth-limiting nutrients such as nitrogen (N) and vitamins.
  • The environmental changes by looking at a small amount of soil as they can represent the entire food web.
  • Threat: Indiscriminate usage in our agricultural fields, posing a major threat to their survival.


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