Parasites (Informational)

Ting, a colleague and a dear friend brought up an unusual topic on our way home this morning. I couldn't recall exactly how it came about but she started wondering, first of all, what cockroaches have to do with our existence. Then, mosquitoes came into the picture. The odd idea that if these insects weren’t in existence, there wouldn’t be any production of insecticides, such as “BAYGON” & “RAID”, just to name a few. And the manufacture of such would involve employment. Then we agreed that a far-fetched purpose for these insects is to generate jobs!

At the back of my mind, I knew that all things and creatures serve a purpose but I wasn’t really thinking as all I was meaning to do was to get home and get some sleep. However, while I was walking on the way to the house I couldn’t get the question off my mind. I knew that sometime in school we were taught about parasites in our Science subject and that roaches and mosquitoes, among others, belong to that group.

Well, it’s been a long time since my brain obtained this knowledge and unfortunately I couldn’t just tap on it at my disposal.

I had to go online and make a little bit of research. Here’s what I found out:

Parasites do play an important role in our vast ecology. They are part of the global food web – 'the circle of life'. Here is why:

Cockroaches eat just about anything. Being omnivore scavengers, they decompose and recycle the organic litter left behind by larger animals. The other big bonus is that cockroaches do not care about what they eat. Possessing a wide variety of bacteria and protozoa in their digestive system, they can eat everything! This is one of the main reasons as to why cockroaches have survived for such a long period of time – 300 million years to be exact. Cockroaches declined in number as the earth’s climate changed periodically, but they are currently thriving due to human impact. The little scavengers live for two things – heat, and a decent feed (both of which we have in abundance). Humans have re-created the Utopia for cockroaches. Our homes are kept warm all year round, and we leave food lying all over the place. To top things off, there are plenty of places to hide for the cockroach – under the stove, in the dishwasher, behind the toaster – the list is endless.

Funnily enough, most cockroaches aren’t pests. There are almost 3,500 species of cockroach in the world, and only 10 are on the World Health Organisation list of human pests. The majority of the cockroaches do not care about humans and their houses – choosing instead to recycle the waste products that are left outside. They also serve as food to small mammals, birds, amphibians and lizards.

*** Posted online by m*STAR (http://www.orble.com/mstar/)

Here’s another one from John Carlson, Medical student, MD/PhD (parasitology) , Tulane University, School of Medicine, discussing about mosquitoes.

Generally, the idea that everything has a purpose assumes that ecosystems are in balance and that all organisms in the ecosystem play a role in maintaining that balance. I believe that you are asking me what purpose mosquitoes have in maintaining balance in an ecosystem.

In a classic example of a balanced ecosystem, there is a prairie of grass, rabbits that eat the grass, and wolves that eat the rabbits. If there were no wolves, the rabbit population would get too large, eat up all of the grass, and then starve themselves to death. If the rabbits were not there, then the grass would not be trimmed, trees would take over the prairie, and the ecosystem would be lost. In this example of a balanced ecosystem, every animal is necessary for the survival of the ecosystem. If one of the organisms is gone, then the ecosystem will collapse. Each of these organisms have a purpose, as most people would define it.

Now let us add a parasite to this system. Let's say that ticks feed on both the wolves and the rabbits. This takes blood away from both the predator and prey, and makes the animals less energetic. The animals won't be sick enough to stop their important role in balancing the ecosystem, but there might be fewer numbers of them. Is the tick important? The tick really doesn't have a role in balancing the ecosystem. It could be said, therefore, that ticks do not have a purpose.

Let's go one step further and say that a certain bacteria infects the rabbits. In order to get from inside one rabbit to inside another rabbit, the bacteria must be transported by a tick. In that case the tick has a purpose for the bacteria. But neither the tick nor the bacteria have a role in balancing the ecosystem.

Now let's say that a scientist comes and collects some of the ticks. She takes the ticks back to her laboratory and finds a chemical inside them that is useful in treating humans with heart disease. She collects more ticks and uses them to make a new medicine that saves many lives. Now the tick has a purpose to humans.

Let's say that an ecologist goes into the ecosystem and discovers how the bacteria get moved from one rabbit to another through the tick. He studies the ways in which the bacteria lives, and then writes a scientific article on the interesting life of the bacteria. Other people read about this interesting bacteria, and it is very inspiring to them. The bacteria has a purpose to the people who find it interesting.

The mosquitoes that were biting you in Coasta Rica probably do not have a purpose in maintaining the balance of the ecosystem there. Some may be eaten by frogs or fish, but there are plenty of other insects for those animals to eat. If all of the mosquitoes were killed, the ecosystem would probably not suffer, unless the poisons used to kill them also killed organisms that are required for the balance of the rainforests. (This is one very difficult problem with trying to control pest insects!)

No one knows, however, all of the secret chemicals those mosquitoes might have. One day, one of the chemicals inside a mosquito might be used to make a new drug. If all of the mosquitoes were killed, scientists would never have the chance to find out.

Also, mosquitoes have many fascinating life styles. They carry many fascinating parasites between different animals. So for people who love to learn about the strange way that life works, those mosquitoes have a purpose that way too.

*** Taken from http://www.madsci.org/posts/archives/2000-09/968278449.Gb.r.html