LEARN FROM ENVIRONMENTAL QUESTIONS
by Whit Gibbons
October 7, 2007
ran across an email of an environmental question and answer from a decade
ago that was of particular interest because I learned some biology myself.
A "mystery animal" had been discovered after heavy rains.
The "mystery animal" was described in the following way: "A
young boy discovered a specimen that our neighborhood is unfamiliar with.
It is 18 to 24 inches in length and has the diameter of a toothpick from
head to tail. It is brown in color and has a flat nose and forked tail.
It was found in a dirty puddle after we had excessive rains. We live in
a South Carolina farming community. Do you have any idea what this may
if she could mail it to me in a jar with tiny air holes in the top and
damp paper towels inside. When I arrived at work two days later, my co-worker
Sarah Collie sat with a jar in her hands and a bemused look on her face.
"Your worm arrived," she allowed.
it was, and exactly as described--two feet of slender worm with a forked
tail and looking like a tangled coil of thin, copper wire. I had never
seen a live one before, and neither had most of the other ecologists I
checked with. However, as biologists, we had all read about such animals
in textbooks. I emailed my new pen pal that the animal was a horsehair
worm, belonging to a poorly understood group, the hairworms, with more
than 300 species. In fact hairworms are in their own separate phylum whose
biological relationship to other worms is unknown. The forked tail on
this one meant it was a mature male.
stage, which can reach a length of three feet, is a free living form,
meaning it is not parasitic. One feature of hairworms is the paradox that
they are special because they are so unspecialized. They have no digestive
system, no respiratory system, and no circulatory system. Adult horsehair
worms do not eat, but after leaving the insects they grew up in, the males
and females mate and reproduce in water. The female lays eggs that float
in the water. If an egg is eaten by an insect, the egg hatches and the
tiny parasite larva drills its way out of the insect's intestine and takes
up residence in the body cavity. It feeds on the inside of the insect
until it grows into a long worm ready to start the process again.
that serve as hosts for hairworm parasites include millipedes, spiders,
and insects, such as aquatic beetles, mosquitoes, crickets, and praying
mantises. Fortunately, none of these hairworm parasites seems to have
any use for humans. However, in what might appear to be the inspiration
for the movie "Alien," the larvae grow to the size of giant
worms inside the unfortunate invertebrate host before they emerge. Imagine
a three-foot long worm inside of a grasshopper!
the worm know it will end up in water so it can mate? A remarkable study
by several French scientists on hairworms that infect crickets and grasshoppers
may offer part of the explanation. In laboratory studies that examine
proteins inside of cells, including the brain of insects, the investigators
found that the hairworm parasite actually alters the behavior of the insect
by producing molecules that enter the insect's central nervous system.
Although the exact mechanisms are unknown, the chemical alteration of
a cricket's or grasshopper's brain makes it want to jump in the water
and drown. Clearly such abnormal behavior for an insect works to the advantage
of the parasite. Brainwashing at its best.
The next mystery to be solved about these strange creatures is whether
the worms produce chemicals that make an insect want to drink from the
water where the eggs are laid. How else would an egg end up in a cricket?
email from the woman with the horsehair worm showed the kind of enthusiasm
about the living world and nature that I like to see in people. "Thank
you so much for all of your attention to this effort. I learn something
new every day!" So do I.
you have an environmental question or comment, email