Little is known about extra thin hairworms
IGOT a hairworm to identify. Hairworms are creatures about which little is known. As their name tells us they are worms that are exceptionally thin. Also called ' horsehair worms', they are found on farms in wet places like drinking troughs, puddles in laneways and ruts in trackways.
It was believed in the past that they arose spontaneously when hairs from a horse's tail fell into the water. Some believed that they grew up to be eels.
A hairworm does not have a body composed of segments like an earthworm and is typically about one millimetre in width and 100-200mm in length. To the unaided eye its body appears like a featureless thick hair. However, it is an active creature. It swims in a slow, snake-like way so the forward-moving end can be identified as its ' head'. The rear end is forked in males; not so in females. Otherwise the body appears totally featureless.
Hairworms belong to a distinct group of worms called Phylum Nematomorpha. Worldwide about 300 species have been described. As adults, most live in freshwater; only five species have been recorded from seawater. It is believed that possibly up to 2,000 species may await discovery.
Only three species have been reported from Ireland but it is not known how common they are or how widely distributed they are. Identification to species level is complex as it involves scanning electron microscopy. All of the freshwater species are called gordiids as these ultra-skinny worms often tie their extremely long bodies into Gordian knots.
The Gordian knot is a knot tied by King Gordius in an ancient Greek legend. It was prophesied that whoever could untie the knot would rule Asia. Rather than untying it, Alexander the Great slashed through the knot with his sword giving rise to the phrase ' to cut the Gordian knot', meaning to solve a tedious problem by swift and forceful action.
Adult hairworms are free-living in water. They mate communally, males and females twining together in a large, tight, ball-shaped Gordian knot. The young are parasitic. They are equipped with hooks and they use these to attach themselves to beetles, dragonfly nymphs, other insects and crustaceans.
The parasitic young live inside their hosts until they reach adulthood. They then leave their hosts and swim freely in water searching for a mate. The adults don't eat; their only purpose is to reproduce before their energy reserves run out and they die.
- JIM HURLEY
