I am aware that for most of the
feminine readers of my blog, subject matter of this post is not
likely to be very palatable, yet I have found it so interesting that
I would request them to suppress their natural aversion and continue
reading it because the facts are absolutely amusing. I am writing
here about Roaches, Cockroaches to be precise.
Perhaps there is no other organism,
which is found everywhere on this globe. Cockroaches have been here
from the Carboniferous period or from 354–295 million years as
fossils from this period have shown their presence. They come in all
kinds of shapes, sizes and packages. There are about 4,600 species
of cockroaches against 5400 species of mammals and only 30 species
from this long list are considered as pests. The world's smallest
cockroach is only 0.3mm long and lives in ant nests. The heaviest
cockroach is the huge Australian Rhinoceros Cockroach that grows to
length of 8 centimeters.
A team from North Carolina State
University in US, led by Dr Coby Schal has been studying cockroach
behaviours for more than 2 decades. Researchers from this team first
noticed 20 years ago, that some pest controlling poisons were failing
to eradicate cockroaches from households and other properties,
because the insects were simply refusing to eat the bait. The team
decided to take up a study of cockroach behaviour to food.
In an article published in the journal
Science, Dr Coby Schal has explained the results of this new study
that has revealed a "neural mechanism" in cockroaches
behind this refusal. Dr. Schal's team carried out experiments in two
parts. In the first part of the experiment, the researchers offered
the hungry cockroaches a choice of two foods - peanut butter or
glucose-rich jam [known as jelly in the US]. Dr. Schal writes "The
jelly contains lots of glucose and the peanut butter has a much
smaller amount.” Surprisingly researchers found that " The
mutant cockroaches tasted the jelly and jumped back. They were
repulsed and then they swarm over the peanut butter."
In the second part of the experiment,
the scientists immobilised the cockroaches and used tiny electrodes
to record the activity of taste receptors (cells that respond to
flavour that are "housed" in microscopic hairs on the
insects' mouthparts.) By analysing the electrical impulses, the team
was able to find out exactly why the cockroaches were so repulsed
from eating sweet food.
There are specific cells in the mouth
of all animals and insects that respond to a specific taste such as
bitter, sweet etc. In case of these cockroaches, the cells that
normally would respond to bitter compounds were actually responding
to glucose, which meant that they were perceiving glucose to be a
bitter compound. The sweet specific cells also responded in this
case, but cells that responded to bitterness actually inhibited the
cells responding to sweet taste. So the end result was that
bitterness could override sweetness.
Highly magnified footage of these
experiments clearly shows how a glucose-averse cockroach reacts to a
dose of the sugar. Dr. Schal says: "It behaves like a baby that
rejects spinach. It shakes its head and refuses to imbibe that
liquid, at the end, you can see the [glucose] on the side of the head
of the cockroach that has refused it."
I find this extremely amusing. We
humans are told all the time by medical profession and dietary
experts, how sweets and junk foods are bad for our health, but even
with our advanced brains and knowledge, we have not been able to get
away from these foods, whereas a lowly insect has modified itself so
that it can avoid glucose and a possible death by eating along with
it some other poisonous substances used in pest controllers.
The process of natural selection,
discovered by Charles Darwin in 1858 would suggest that over a period
of time, such individual cockroaches, that have by chance the genetic
change that causes them to avoid the sweet bait and therefore death,
would have a greater chance of survival and reproducing. It is
natural that their descendants with the trait would in time, replace
those that lacked the trait in the cockroach population. Dr. Schal
says that this is the same process that has led to the evolution of
antibiotic resistance in disease-causing bacteria, and warfarin
resistance in rats.
According to Dr Schal, this was another
chapter in the evolutionary arms race between humans and cockroaches.
He adds: "We keep throwing insecticides at them and they keep
evolving mechanisms to avoid them, I have always had incredible
respect for cockroaches," he added. "They depend on us, but
they also take advantage of us." Very true!
This household insect, hated most by
almost everyone, thus has won a major battle against sweets that
could lead it to its death, something we humans simply are unable to
do. Even if we hate cockroaches, it is high time that we respect
them.
29 May 2013
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