🐣 Biology

The life-cycle of nematodes and their 6 stages.

Which of the following is not correct regarding nematode?
  • The life cycle of nematode has six stages:
    • Egg: The female lays eggs in soil or in plant tissues, singly or in groups as egg mass that hatch out into larvae.
    • J1 or first stage larva
    • J2 or second stage larva
    • J3 or third stage larva
    • J4 or fourth stage larva (four larval or juvenile stages)
    • Adult stage
  • In plant parasitic nematodes, there are four juvenile stages and an adult stage.
  • The immature stage of the nematode called as juvenile. The first four stages are the immature stages and are known as juvenile stages.
  • Hatching (Ecdysis): The term hatching is used for the emergence of the juvenile from the egg. It occurs either in response of a stimulus or stimuli from the host or take place under normal environment.
  • Moulting: Growth in nematodes is associated with moulting which usually occurs four times and there are five stages.

Voltinism

  • Voltinism refers to number of generations completed by nematode in one year.
  • On the basis of voltinism, nematodes are following types:
    • Univoltine Nematodes: Only one generation is completed in a year. Examples are Angunia tritici and in Heterodera sp.
    • Multivoltine Nematodes: Many generations are completed in a year. Examples are Meloidyne incognita, Tylenchulus sp, Pratylenchus, Rotylenchulus.
References 
- Dropkin, V.H. 1980. Introduction to plant nematology. John Wiley and sons, INC. New York.
- Singh, R.S and Sitaramaiah, K. 1994. Plant pathogens. The plant parasitic nematodes. Oxford & IBH Pub. Co. Pvt. Ltd. New Delhi.
- Parvata Reddy, P. 1983. Plant nematology. Agricole Pub. Co., New Delhi.
- Southey, J. F. Laboratory methods for work with plant and soil nematodes Tech.
- Bull. Min. Agric. Fish. Food. Her Majesty’s Stationary Office, London.
- Walia, R. K and Bajaj, H. K (2014). Textbook of Introductory Plant Nematology. Directorate of Knowledge Management in Agriculture, ICAR, New Delhi. 
- Kumar, V., Khan, M.R. & Walia, R.K. Crop Loss Estimations due to Plant-Parasitic Nematodes in Major Crops in India. Natl. Acad. Sci. Lett. 43, 409–412 (2020). https://doi.org/10.1007/s40009-020-00895-2

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