PARASITE

Have you ever bewailed the lot of the humble parasite? Mayhap you should as they are a much maligned but poorly understood group of biological entities. Let me start with a formal definition: An organism that lives and feeds on or in an organism of a different species and causes harm to its host is considered a parasite. This covers a multitude of organisms from bacteria to vampire bats. But not viruses as they do not constitute life according to strict criteria. It has been estimated that up to 40% of extant species are parasitic to some degree. It appears that, as a biological strategy, parasitism can be profitable. They can be likened to the human economic parasite, Estatus Agentus Twatus Maximus. A most pernicious breed of humankind dedicated to sapping the lifeblood of every human contemplating a change in location. Makes me wanna burn stuff. Moving on…….

Parasites should be distinguished from critters which live in harmonious accord with their host, called commensals. Commensals cause no harm or benefit, or none we can detect. A good example would be the remora fish which attach to sharks to garner morsels of food from prey taken by their gracious host; the ultimate perpetual dinner guest. The next category I would like to consider are species which engage in a beneficial interaction. Mutualism engages both species with benefits without detriment. A good example would be the association of flowering plants with a variety of bee species. In turn for a good feed of nutritious nectar, the bee transfers pollen between plants thus ensuring pollination.

There is contention amongst biologists that given time, a lot of time, parasitic species will eventually, through coevolution, become more in tune with their much suffering host, eventually becoming less malign and therefore entering the stage of commensalism on their evolutionary way to mutualism.  This, of course, is just one scenario. Predictions can only be made if we understand the intrinsic and extrinsic evolutionary pressures, demonstrated, over time. In fact, if there is competition between parasitic species for the same host then drift to a more aggressive form of parasitism may ensue with shorter life cycles for the parasites engaged.

Humans like to classify into discrete entities. For some reason, we are made to view the world this way. Life is not so simple or discrete. Life tends to morph into blurry categories thus predation is but one end of the scale proceeding, by degrees into parasitism, through to the commensal, and ending up with the mutualistic way of life. If only life was this simple.   

Anyway, I’ve provided an example below of the parasitic way of life. This example is said to have swayed Darwin away from a belief in an omnibenevolent deity. In his own words:  "I cannot persuade myself that a beneficent and omnipotent God would have designedly created parasitic wasps with the express intention of their feeding within the living bodies of Caterpillars." Take no heed gentle reader, Darwin’s atheism came as a consequence of his own deliberations in the field of natural selection and evolutionary theory.

Consider the Ichneumon wasp, a most delightful and clinched waist creature with the habit of laying its eggs in butterfly larvae. Once cosseted inside the grub the egg hatches into a wriggling worm which begins to pork out on the tissues of the unfortunate grub. They are mindful not to ingest vital organs leaving the succulent nervous tissue to last. Thus, the grub undergoes a long lingering death as it is consumed from within. Of note, the wasp has engaged the help of a virus that suppresses the host’s immune system. The intruder thus lurks within without being detected by the grub’s innate internal vigilance system.  Isn’t Nature just a complete treasure in all its manifest horrors. Arse.

And so, I would like to finish with part of a poem from the pen of the satirical cleric Jonathan Swift. This excerpt/extract is taken from, "On Poetry: A Rhapsody". Take it away, Jonathan. In this version, the vermin only teaze and pinch.

Their foes superior by an inch.

So nat'ralists observe, a flea

Hath smaller fleas that on him prey;

 And these have smaller fleas to bite 'em.

And so proceeds ad infinitum.

Thus every poet, in his kind,

Is bit by him that comes behind: Ain’t dat the sad truth.  

What do you think of my new tongue?