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Life Cycle of a Nematode

Nematodes are, for the most part, microscopic worms. Some are parasites that feed off of insects, plants and animals. Others live by eating bacteria, fungi and other types of nematodes.

In one handful of soil, there may be thousands of nematodes and hundreds of different types. Within the scientific phylum for nematodes there are 20,000 identified species.

Some nematodes are beneficial. There are types of nematodes that feed on the common flea that infects dogs and cats. Some pet owners are intentionally introducing this nematode into soil as a means of controlling the parasite.

Others are potentially dangerous to human and animal health, however, and include roundworms, whipworms, pinworms, hookworms and other common intestinal parasites.

Despite the many different types of nematodes, the basic life cycle is similar across the various species

  1. Egg

    • Temperature and moisture levels determine when the egg hatches, and the larva will not emerge from the egg until the environment is one that is favorable for survival.

      In some types of nematodes, the parasite will molt for the first time while still within the egg, so it is a second-stage larva that emerges.

      While many types of nematodes do not enter their host until after their third molt in the larval stages, a few species---including many of the intestinal parasites---will enter their hosts while in the egg stage of development.

    Larval

    • The newly hatched larva, called the L1 stage, feeds and grows until it must molt. The molting process will occur four times before the nematode reaches the adult stage.

    Parasitic

    • In many types of parasitic nematodes, the larva will infect its host following its second molt, L2. The infection occurs when the nematode is in the L3 stage of its development.

    Adult

    • The fourth and final molt, L4, will take place within the host in most species. That host may be an insect, plant or animal. Following the final molt, the nematode will be an adult but not yet capable of reproduction.

    Reproduction

    • A final phase of growth makes the adult capable of sexual reproduction and it is only at this final phase in the nematode life cycle that genders are established. The life cycle begins again when the adults reproduce and lay eggs. These eggs usually pass from the host's body and will develop to infect another plant, animal or insect.

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