Cottage Q&A
QUESTIONI found this black, string-like form in the water at our cottage near Killbear Provincial Park. When we put it on a piece of paper it began to twist around into strange shapes. The penny shows its relative size. What is it?
ANSWER
It's an adult horsehair worm, sometimes known as a Gordian worm because, as you discovered, it can twist itself into shapes reminiscent of the Gordian knot of Greek mythology. Sometimes the worms are found clustered together in tangles of hundreds or even thousands. They're members of the strange and wonderful phylum Nematomorpha, a group of parasites whose life cycle is still not entirely understood among scientists.
What is known is that nematomorphs reproduce sexually, laying millions of eggs in long, gelatinous strings around aquatic vegetation near the shores of ponds, streams, and lakes. Once hatched, the larvae embark on an amazing journey. Ingested by another larva (such as that of a mosquito or midge), the worm larva forms a cyst that can survive through the host's metamorphosis into an adult insect. When the insect host is finally eaten in its turn by a cricket or grasshopper, the cyst dissolves and the horsehair worm larva matures into an adult worm. A clever manipulator, the adult then uses chemicals to make its host insect feel "thirsty" and go towards water - whereupon the worm emerges through the host's body wall to become a free swimmer, like the specimen you found. (Surprisingly, the host insect often survives this invasion of its privacy, and carries on to complete its own life cycle.) Adult horsehair worms don't feed, their sole purpose being to find a mate and procreate in order to start the cycle all over again. Sometimes, life is just like that.
* Published in the September/October 2005 issue of Cottage Life
