Tied up in Knots
(Queensland Museum)
As Summer begins, people around Brisbane (and elsewhere) sometimes find in their swimming pool, or the dog's water bowl, a tangled mass of worms looking like bits of knotted wire or horse hair. Occasionally a dead grasshopper or preying mantis is found nearby.
The worms are Gordian worms (Phylum Nematomorpha) and are related to the round worms (Phylum Nematoda). The juveniles are parasitic in insects. If an insect ingests the larvae while feeding or drinking the parasite penetrates through the gut wall into the body cavity. The developing worm has no mouth or gut and simply absorbs nutrients directly through its skin.
When the worm is mature it occupies almost all of its host's body and it is thought that it somehow induces the insect to seek out water. Once there, the worm emerges from the insect, which is reduced to a mere husk.
This emergence is a horrifying sight and some people who have contacted the Museum are convinced that they have witnessed an alien invasion. In the water, the worms find a mate and the females lay eggs from which the larvae emerge about a week later. Gordian worms can be deadly for insects, but are harmless to us and our pets.
These worms are rather stiff and can get themselves into quite a knot as they slowly twist and turn. They get their name 'gordian' from the famous knot of antiquity, which Alexander the Great cut with his sword before he went on to conquer Asia.
Want to know more about these fascinating parasites? Download the Gordian worms fact sheet from our Inquiry Centre or see Wildlife of Greater Brisbane, published by the Queensland Museum.