Print This Page

 Major Groups | Nematomorpha (horsehair worms)

Nematomorpha (horsehair worms)

The order Gordioidea takes its name from the mythical Gordian Knot. This is seen when several adult individuals tangle together to form a knot.

Descriptive Features:

  • mouth absent or present but not functional
  • worm-like body, thin, cylindrical, unsegmented, colour yellow to dark brown
  • cuticle often ornamented by small, numerous, specialized thickenings of varying size and shape bearing setae, bristles and pore openings
  • in some genera, male posterior is bifurcate
  • Total length: extremely long individuals, 10 - 100 cm, males smaller than females 

    Distribution: Eastern Australia

    Sensitivity Rating: SIGNAL grade 6

    Functional Feeding Group: parasites


    Billabong Creek, Walla Walla NSW

    Ecology: Adult horsehair worms occur in flowing and shallow standing waters. They are free living in water for several months. Sexes are distinct and fertilisation is internal after copulation. Males die after copulation and females die after egg laying. Thousands of eggs are laid in a mucilaginous string. They hatch after several weeks to microscopic larvae. These larvae encyst at the waters edge where they are eaten by terrestrial and aquatic insects. If not eaten the cysts eventually die. Larvae and juveniles are parasites in the main body cavity of the host, directly absorbing food and digested tissues through its body wall. Horsehair worms grow to become a tightly coiled mass killing the host, then it penetrates the host's body wall and returns to the water.


    Information Sources: Williams 1980, Hawking & Smith 1997


    Nematomorpha emerging from its grasshopper host