If you have read Part 1 you will have realised that the tortoise wasn’t actually a tortoise, it was a terrapin, some might even argue a turtle, but hey I’m no expert! On the day between the stakeout and the capture of the terrapin we were out on an INNS patrol controlling Himalayan Balsam and Japanese Knotweed. Accessing a stand of balsam on the opposite bank something caught my eye in the clear shallow water, something stuck on a rock wafting in the current but not moving completely as one might expect. Closer inspection identified the mystery spaghetti like object as a Horsehair worm.
Horsehair worms also known as Gordian worms because of the tangles and knots that they form on their own or in the company of other worms.
In some species like the one in the video, a bifurcated (forked) tip at the posterior end is visible.
There are four stages in their life cycle: the egg, the pre-parasitic larva, the parasitic larva, and the adult.
Parasitizing an insect or another arthropod is always involved the most common host being crickets, grasshoppers, and cockroaches.
The parasite obtains nutrients from the body fluids of the host as it changes into an adult worm. The worm is tightly folded to fit inside the insect and may fill most of the animal’s body cavity. (The one in the video is just over 30 cm long.)
Eventually, the worm exerts control over its host’s behavior and somehow triggers the insect to seek water. Some scientists have suggested that the insect may become very thirsty under the worms influence, causing it to rush towards a water source. The mechanism of this behavioral control isn’t fully understood, though it may be by the production of chemicals inside the insect’s body.
Once the infected insect enters the water, the worm emerges through a hole that it creates in the animal’s body. The adult worms do not feed and exist only to continue the next generation.
Not quite as cute as the terrapin but fascinating, nonetheless.
So, there you have it, two very different days working with the Forth Rivers Trust.