The curious case of the worm

Is it a blind snake, a weird earthworm or just a long thick piece of hair that somehow wriggled and moved?

 

Umesh was almost convinced it was some kind of a snake. I was not so sure. I had never seen anything like it before. It was very long, almost a metre, thin, dark, and cylindrical; both its ends looked similar although we figured out which was which. It hardly seemed like a living creature, more like a dry coiled up thread. In any case, the possibilities excited all of us.

We were on our way to the Lisu village of Gandhigram walking the usual route through Namdapha National Park in the Eastern Himalayan Arunachal Pradesh. My doctor friends, Prashanth and Umesh, who appear more interested in birds than in humans, were accompanying some of us to the Lisu villages lying beyond the eastern boundary of Namdapha. This was our fourth day of plodding through knee-deep mud and slip-sliding along. On a relatively easy and dry stretch, Prashanth and Umesh were ahead and saw this creature lying near a puddle on the roadside and shouted to us.

We put the creature on a big Colocasia leaf and with our digital cameras took countless pictures, while it wriggled. The Lisus stood around amused. Duchaye said that they had a name for it in Lisu which meant ‘wood-worm’ because it appears as if it is made of wood. But they could not tell us anything more.

More clues!

Back in Miao, I showed Japang, an old friend and elephant mahout, the pictures. He told me a long story of how he had observed creatures like this coming out of beetles! He had wondered if they were beetle young. I was baffled by this, but Japang’s observation skills in the jungle are second to none. But this time I wondered if he knew what he was talking about.I got back two months later and sent the photos to another friend who definitely ‘knows his worms’. He informed me that it was a horsehair worm.

Getting to know more

I searched on the internet and found there were 230 species worldwide. They apparently have no close relationship with any other living organisms. They can be confused with parasitic worms of the order Nematoda, so the thing to do is to look at the tail end; parasitic nematodes have a hooked end, while these worms have a cleft.

Worming out the details

As usual Japang’s ‘story’ was also true – these worms are parasitic as larvae, usually on grasshoppers, crickets, cockroaches, locusts, katydids, beetles, and a host of other species including some vertebrates. The larva enters a host (how they enter is not yet known), eating and digesting the host’s tissue, and emerges only as an adult, breaking through the body wall of the host. It does not generally kill the host but may impair reproduction. It needs water when emerging, and newly emerged worms need to be near water, otherwise they apparently die.

What’s in a name?

Long ago, people christened them horsehair worms, because they believed that hairs falling from horses’ tails into water troughs spontaneously transformed into living worms! Actually, insects that fell into the water would become parasitized by larvae of these worms which would later emerge as adults. So it seemed that the fallen horse hairs had somehow become worms.

Master of escapes

That was not all. These creatures, which I had never heard of, re-appeared in my life a few days later making headlines in the papers. These remarkable creatures are able to do a Houdini. When their host is eaten by a predator, they can do a double escape.

French scientists reported that these worms can emerge from their host, say, an insect and then from the mouth, nose or gills of the fish or frog that ate the insect. But they have to do it fast – within five minutes of its host being eaten – otherwise they don’t make it.


This article appeared in the Hindu in School on 19 December 2012.

Picture: Into the light at last! A horsehair worm emerging from a katydid host.
Credit: Wikimedia Commons