VIROCELL CONCEPT APPLIED TO PARASITES

 

Virocell Concept Applied To Non-Viral Parasites

Post # 33

Donald A. Windsor

Viruses that harm their hosts are parasites. The popular notion that viruses are not alive has been dispelled by Patrick Forterre with his virocell concept (1, 2, 3). A virus is composed of a virion and a virocell. The virion is a protein capsule that contains a nucleic acid genome. The virocell is the host cell that accepts a virion and then produces more virions. The virus is the living organism. The virion is the equivalent of a plant seed.

If non-viral parasites (hereafter just called parasites) were regarded this way, the definitive host and its parasite, together, would be the living organism. The definitive host would be analogous to the virocell and the parasite would be analogous to the virion. The parasite would also be analogous to a seed.

Admittedly, this is an unconventional way of considering parasites.

But, it is consistent with my concept of considering parasitism as a property of life (4).

It is also consistent with my concept of the biocartel, first reported in 1997 (5).

A lot more thought has to go into this concept. For instance, some parasites have intermediate hosts in their life cycles. Do some viruses have intermediate virocells? Parasites may or may not reproduce in their intermediate hosts. Sometimes the intermediate host serves simply to transmit the parasite to its next host.

References cited:

1. Forterre, Patrick. Manipulation of cellular syntheses and the nature of viruses. The virocell concept. Comptes Rendus Chimie 2011; 14: 393-399.

2. Forterre, Patrick. The virocell concept and environmental microbiology. The ISME Journal [International Society for Microbial Ecology] 2013; 7:233-236.

3. Forterre, Patrick. Viruses in the 21st century: from the curiosity-driven discovery of giant viruses to new concepts and definition of life. Clinical Infectious Diseases 2017; 65 Supplement 1: S74-S78.

4. Windsor, Donald A. Parasitism as a property of life. Parasites Dominate 2013 September 3; Post #2. http://www.parasitesdominate.blogspot.com

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

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ARE PARASITES SINGING THEIR OWN UNCEASING SONG OF LIFE?

Are Parasites Singing Their Own Unceasing Song Of Life?

Post #30

Donald A. Windsor

Well, parasites may not be singing, but they sure are showing off their most visible presence – biodiversity.

James Lovelock referred to the infrared signal of the oxygen-methane disequilibrium radiating from Earth's atmosphere as an "unceasing song of life".

"This unceasing song of life is audible to anyone with a receiver, even from outside the Solar System." (1).

If Lovelock's statement is correct, then this song would indicate life on any extraterrestrial entity.

After such life is found, perhaps it could reveal whether parasitism is, or is not, a universal property of life. I suspect that it is.

Here on Earth, our life exhibits parasitism. But, what would life look like without parasitism? I suspect that the signature hallmark of life is biodiversity. But biodiversity can result from life adapting to environmental forces, such as competition, predation, habitat, and climate.

Parasites enhance biodiversity by thwarting monocultures. Therefore, the absence of monocultures on extraterrestrial entities could be a signature of parasitism.

However, how would a monoculture be recognized? On Earth we have no naturally occurring pure monocultures; they exists only in labs or buildings. Our so-called monocultures, such as with agricultural crops like corn and wheat, always have other species living among them.

Here is a handy metric that I propose. In a monoculture, the number of individuals of one species is at least 1 magnitude higher than the total number of individuals of all the other species combined, in the same area.

For example, if a bean field had 10,000 individual bean plants, then it would be a monoculture if the total number of individuals of all the other species in that field was under 1,000, a difference of 1 order of magnitude.

This metric would not be able to compare macro-species with microbial species, because the microbes would always outnumber the macros. However, it may be useful in comparing a monoculture of a microbe with other microbial species.

So, while the unceasing song of parasitism may not be a song, it may be an image visible to anyone with a viewer.

Reference cited:

1. Lovelock, James. The Ages of Gaia. A Biography of Our Living Earth. 2nd Edition. New York, NY: Oxford University Press. 2000. 268 pages. Quote on page 7 of the Introductory.

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PARASITE BENEFITS HOST: COPEPOD ON SHARK EYES

PARASITE BENEFITS HOST: COPEPOD ON SHARK EYES

Post # 12

Donald A. Windsor

The copepod parasite that attaches to the eyes of Greenland and Pacific sleeper sharks seems to be too harmful to persist through evolution. Surely animals with their vision impaired by this parasite would be at such a competitive disadvantage that they would not live long enough to reproduce. Yet they do. In fact, Greenland sharks (Somniosus microcephalus) are the longest lived animals (1).

The standard story is that Somniosus sharks do not depend upon their eyesight to feed and reproduce (2). But, what if they did depend on their parasitic copepod?

Perhaps the copepod parasite (Ommatokoita elongata) confers some benefit to its shark hosts. I have long wondered about parasites conferring benefits to hosts but see it at the species level (3). Maybe this grotesque case of the shark and the copepod provides an example at the individual level. In fact, also at the species level because almost all individual Greenland sharks, 99%, are parasitized by this copepod (4).

Such a high level of infestation makes me wonder if this copepod is functioning as an organ. If so, then it is benefiting its host. Berland calls it a mutualism (4). Of course, all mutualisms benefit their hosts, by definition.

Perhaps the copepod acts as a vision enhancer that enables its shark to see better. Perhaps the copepod is very sensitive to vibrations and transmits the changes in vibrations into the eye and directly to the brain.

Many aquatic animals that dwell in murky water have appendages (catfish) or whiskers (seals) that do the same thing. Some aquatic animals send out electric pulses (eels, platypus) to assist their vision. Perhaps these copepods are involved in a similar process.

Perhaps in the distant past, the Greenland sharks were losing their eyesight and only those individuals that had this copepod parasite were the ones who survived.

The best explanation (so far) seems to be the one offered by the anonymous Norwegian fishermen who told Berland (4). They claimed that the parasitic copepods lure prey to the sharks. These fishermen contended that the copepods were luminous, but Berland could find no evidence for this claim.

Greenland sharks are very sluggish and Berland wondered how they managed to catch anything to eat. So luring prey, rather than chasing it, may indeed be the answer. The chief meal in Berland’s 1961 investigation was Char. However, Neilsen in 2017 reports that seals were a common food (1).

My conclusion to this bizarre case is that perhaps what we often call parasitism is really mutualism.

References cited:

1. Nielsen, Julius. Dating a Greenland shark. Natural History 2017 February; 125(2): 10-13.

2. Benz, George W. ; Borucinska, Joanna D. ; Lowry, Lloyd F. ; Whiteley, Herbert E. Ocular lesions associated with attachment of the copepod Ommatokoita elongata (Lernaeopodidae: Siphonostomatoida) to corneas of Pacific sleeper sharks Somniosus pacificus captured off Alaska in Prince William Sound. Journal of Parasitology 2002 June; 88(3): 474-481.

3. Windsor, Donald A. Parasites benefit their hosts – at the species level. parasitesdominate.blogspot.com Post #7 on 16 March 2014.

4. Berland, Bjørn. Copepod Ommatokoita elongata (Grant) in the eyes of the Greenland shark – a possible cause of mutual dependence. Nature 1961 August 19; 191(4790): 829-830.

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PARASITISM ON MARS

Post #10

PARASITISM ON MARS

Donald A. Windsor

Parasitism is a property of life on Earth, because most of our species are parasites (1). However, what about life on other worlds? We are on the verge of discovering life on Mars. Will Martian life have parasites?

If parasitism is a universal property of life, then it should occur in Martian life.

If Martian life does not have any parasites, then parasitism is unique to Earth. It would have to be decided on how many potential host species would have to be examined before it could reasonably concluded that no parasites occur.

Meanwhile, we should avoid contaminating the Martian biosphere, in case it has one.

1.  Windsor, Donald A.  Most of the species on Earth are parasites. 

 International Journal for Parasitology 1998 December; 28(12): 1939-1941.

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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