PARASITE COOKIES ON HOST GENOMES

Donald A. Windsor    Norwich, NY

Post #6

Hosts seem to be unable to repel parasites at the species level. If they were able, they would be parasite free, which they are not. In fact, some parasites have coevolved with their hosts in a continual arms race to the point where the hosts seem to be addicted to their parasites.

Why? Why is parasitism a property of life? Why is it so widespread? What is it that parasites do to maintain the susceptibility of their hosts? Why cannot hosts evolve to repel the parasites that harm them?

Predation is a property of life, but it is external to the prey, so the prey cannot do much about it. But parasitism is based on easy entry, so hosts do have a chance to thwart entry. Perhaps parasitism is a form of predation. But, even if it is, it is different enough to warrant special study.

Perhaps parasites put "cookies" on their hosts' genomes. Cookies are programming codes that one computer puts on another computer to recognize it. Perhaps parasites insert genetic, or epigenetic, material into their hosts' genome. These parasite cookies would allow free passage into or onto their hosts' bodies.

Other symbionts besides parasites might also use cookies.

Sure, this is speculation on my part, because I have no data to support it. However, I prefer to regard it as a working hypothesis, one that can be tested by looking for parasite cookies.

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DARWIN'S ENTANGLED BANK IS MAINTAINED BY PARASITES

Donald A. Windsor

Post # 5

Charles Darwin (1809-1882) found it "interesting to contemplate an entangled bank" (1).  So too do I.  However, I see something that Darwin did not.  I see the actions of parasites.  For without parasites, our entangled banks would be uninteresting monocultures.  Sometimes monocultures do take over banks; Kudzu, the invasive alien from Japan, is a splendid example (2).  But not to worry, because eventually pathogenic parasites will strike and once more the bank will regain its entangled diversity.

I was first exposed to Darwin's entangled bank while a grad student in 1959, when our department celebrated the centennial of the Origin of Species.  About two decades later, when I began serious investing, the stock market seemed to be an entangled bank.  Adam Smith (1723-1790) invoked his "invisible hand" as a very apt metaphor to depict market activity (3).  I put Darwin and Smith together and then wondered what Darwin's invisible hand might be.

Almost two decades later I was studying systems science (math and computers), so I saw Darwin's invisible hand as an emergent property of ecosystems, a case of the whole being more than the sum of the parts.  End of story.  Or so I thought.

But then I experienced a powerful epiphany.  My dissertation research in the 1960s involved blood-feeding parasites (4).  Unfortunately, I had to give up parasitology to earn a living.  I worked as an information scientist in pharmaceutical research.  When I retired in 1994, I tried to catch up with the past three decades of parasitology literature.  I rapidly read through it in a year and a half.  This fast-forward approach led me to this epiphany moment.

I realized that parasites actually ruled the biosphere and that parasitologists were so preoccupied with their day to day activities that they were not seeing the big picture.  That was when I created the concept of biocartels (5) and then realized that most of the species on Earth are parasites (6).

However, I still wondered why.  Now (finally) I think I know.  Parasitism is an inherent property of life (7).

I also now realize that the invisible hand managing Darwin's entangled bank is the vast insidious handiwork of parasites.  Without parasites, biodiversity would be much less diverse.

References cited:

1.  Darwin, Charles.  On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.  First Edition. 1859.

2.  Niering, William A. ; Olmstead, Nancy C.  Kudzu vine (Pueraria lobata).  In:  The Audubon Society Field Guide to North American Wildflowers.  Eastern Region.  New York, NY: Alfred A. Knopf.  1979.  Page 538.

3.  Smith, Adam.  ["Invisible hand."] In: An Inquiry into the Nature and Causes of the Wealth of Nations.  1776.  Everyman's Library version by Alfred A. Knopf, New York, NY.  1991.  Page 399.

4.  Windsor, Donald A.   Faeces of the medicinal leech, Hirudo medicinalis, are haem.  Nature 1970 September 12; 227(5263): 1153-1154.

5.  Windsor, Donald A.  The basic unit of evolution is the host-symbiont "biocartel".  Evolutionary Theory 1997 Aug; 11(4): 275.

6.  Windsor, Donald A.  Most of the species on Earth are parasites.  International Journal for Parasitology 1998 December; 28(12): 1939-1941.

7.  Windsor, Donald A.  Parasitism as a property of life.  Frontiersin.org/blog/Parasitism_as_a_Property_of_Life/356

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NINE HYPOTHESES ABOUT PARASITISM

Donald A. Windsor

Post #4

Parasitology is a descriptive and experimental field.  However, enough information has been accumulated to enhance it with a theoretical component.  So I present here nine hypotheses for testing.

1.  Most of the species on Earth are parasites. 

2.  Parasitism is an inherent property of life.

3.  Parasites harm their individual hosts but can benefit their hosts at the species level.

4.  Parasites can transfer genetic and epigenetic material between host species, even between hosts in different kingdoms.

5.  Sex evolved from parasitism.

6.  Parasites are drivers of speciation.

7.  Parasites are drivers of biodiversity.

8.  Parasites are drivers of ecosystems.

9.  Parasites are drivers of evolution.

I suspect that there are more hypotheses, but I will deal with these for now.

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PARASITISM IS A FORM OF PREDATION

Donald A. Windsor

Post #3

From the beginning, life seems to have been based on the consumption of nutrients.  The wide range of different processes for obtaining those nutrients is reflected by the vast biodiversity on Earth.  Many organisms have specialized in obtaining nutrients by consuming other organisms through predation.  Many parasites prey upon other organisms by an intimate form of predation.

Needless to say, but predation harms the prey and parasitism harms the host.  The differences between predation and parasitism are dependent on the situation.  Predation can be fatal to animal prey whereas it is usually not fatal to plant prey. 

I am not merely playing with words here.  The distinction between a predator and a parasite became very real to me when I was working with an undeniable parasite, Paragonimus kellicotti, a lung fluke in mammals.  This trematode ingested host blood from its position in its host's lung. 

I wondered how its tetrapyrrole metabolism compared to that of the blood-sucking leech, Hirudo medicinalis.  I wanted to use the leech as an easier to raise stand-in for the fluke.  But is this leech a predator or a parasite?  Is the female mosquito a predator or a parasite?  Mosquitoes consume a blood meal in just a minute or so.  In my lab, leeches fed on guinea pigs for a few hours to over a day.  The lung fluke can persist in place for years.  Is the difference between a predator and a parasite a mere matter of time?  Or is it internal versus external?  How about a blow fly maggot eating dead flesh on a living host?  Or an ichneumon wasp larva developing in a live caterpillar?  What about fleas and ticks? 

If it is difficult to make a distinction between predation and parasitism, then perhaps there is no distinction, just a spectrum.  If indeed that is the case, then because predation is certainly a property of life, parasitism is also a property of life.

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PARISITISM AS A PROPERTY OF LIFE

Donald A. Windsor,   Norwich, NY                                                          Post #2

If every living species were either a host or a parasite or both, then there would be no doubt that parasitism was an integral property of life.

Unfortunately, every living species has not been studied to the depth necessary to ascertain this information. However, enough species have been, so it does seem reasonable to make this assumption.

Why bother? Because the opportunity to see if this property is restricted to Earth, or is universal. Mars is currently being investigated. All properties of life should be looked for. If parasitism is found on Mars, then we can be more confident that parasitism is a universal property of life.

If life without parasitism is found on Mars, then we will be able to see why life on Earth carries such a parasitic burden.

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