Friday, July 19, 2019


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.


Saturday, June 29, 2019


Did Humans Originate From Manipulation By Parasites?
Post #29
Donald A. Windsor

Humans are very different from other hominid primates. How did we get this way?

The Savanna Hypothesis postulates that our ancient ancestors abandoned their arboreal life to live in a savanna, a habitat with mostly grass and few trees. It attributes our upright posture and bipedalism to this change of venue. Our keen intellect, organizational skills, and language evolved in this savanna habitat (1).

I suspect that parasites instigated this transition from arboreal to terrestrial.

My suspicions were aroused by the model of the pill bug and the bird. The acanthocephalan Plagiorhynchus cylindraceus is parasitic in its definitive host, the European Starling Sturnus vulgaris, and in its intermediate host, the isopod "pill bug" Armadillidiuum vulgare. The parasite manipulates the pill bug to behave in ways that increase its chances of being eaten by the bird, Normally, pill bugs prefer dark, humid, covered places. Infected pill bugs tend to wander out into the open where it is lighter and drier, where they become easy prey for the bird (2).

Could some arboreal hominids have been manipulated by a parasite to venture into the more dangerous savanna? How similar is the pill bug and bird example to an early hominid coming down from the safety of an arboreal lifestyle to roam in the dangerously open savanna? While there may be no way of knowing for certain, the possibility is intriguing.

Consider that the parasite Toxoplasma gondii is notorious for manipulating humans. Moreover, its definitive host is felines (3). Large feline predators inhabit grasslands. Its intermediate host is an array of prey animals, especially rodents (4). Humans could be an intermediate host.

I pose this hypothetical parasite involvement because the Savanna Hypothesis has been discussed for over two centuries and, while it may be out of favor now, it still has merits. Besides, numerous migrations allowed humans to become a cosmopolitan species. Parasites could well have been instrumental in moving people around.

References cited:

1. Anon. Savannah hypothesis. Wikipedia 2019 June 9: 1-7.
2. Moore, Janice. Responses of an avian predator and its isopod prey to an acanthocephalan parasite. Ecology 1983 October; 64(5): 1000-1015.
3. Anon. Toxoplasma gondii. Wikipedia 2019 June 13: 1-23.
4. Tenter, Astrid M. ; Heckeroth, Anja R. ; Weiss, Louis M. Toxoplasma gondii: from animals to humans. International Journal for Parasitology 2000 November: 30(12-13): 1217-1258.

Wednesday, June 12, 2019


Hemiparasites Benefit Their Hosts At The Species And Ecosystem Levels
Post #28
Donald A. Windsor

Hemiparasites are photosynthetic plants that parasitize free-living plants to obtain nutrients (1).

Growth of the host plants can be stunted by the hemiparasites, thus allowing more sunlight to reach lower growing plants and increasing biodiversity.

Hemiparasites benefit prairie ecosystems similar to the way grazing animals do, by preventing the taller plants from taking over. For this reason they are sometimes called "pseudograzers" (2).

Individual hemiparasites harm their individual hosts, but the hemiparasites as species benefit other species, and the resulting biodiversity benefits the ecosystem. All species in the ecosystem benefit from the ecosystem staying intact.

References cited:

1. Těšitel, Jakub ; Plavcova, Lenka ; Cameron, Duncan. Interactions between hemiparasitic plants and their hosts: The importance of organic carbon transfer. Plant Signaling & Behavior 2010 August; 5(9): 1072-1076.

2. DiGiovanni, Jane P. ; Wysocki, William P. ; Burke, Sean V. ; Duvall, Melvin R. ; Barber, Nicholas A. The role of hemiparasitic plants: influencing tallgrass prairie quality, diversity, and structure. Restoration Ecology 2017 May; 25(3): 405-413.


Saturday, May 18, 2019


Deep Subsurface Biosphere ─ Any Parasites?
Post #27
Donald A. Windsor

As even more information comes in on the deep subsurface biosphere, the more I wonder about generalities already made about our surface biosphere.

The deep subsurface biosphere is composed of archaea, bacteria, and eukaryotes that live underground down to great depths, even under the oceans (1 - 6). It could have more species than our surface biosphere does (2).

Six years ago I proposed that parasitism was a property of life on Earth and if it is found on extraterrestrial planets, it would be a universal property. If it were not found on other planets, then it would be a property of Earth alone (7).

So far, I have not uncovered any reports of parasites in the deep subsurface biosphere.

In 1998 I proclaimed that most of the species on Earth were parasites (8). If there are no parasites in the deep subsurface biosphere, my hypothesis would be nullified. However, I did say "on" Earth, not "in". Nevertheless, I meant "on", because I was not aware of how massive the deep subsurface biosphere is.

Another thought I advocated is that parasites produce biodiversity by stopping monocultures before they get too large (9). Some of the colonies in the deep subsurface may have monocultures. That in itself could indicate a lack of parasites.

I find this all very exciting because I thought that finding extraterrestrial life on Mars would be a test of my hypotheses (10). But now the deep subsurface biosphere may provide that test.

References cited:

1. Lawton, Graham. Earth's deep, dark secret. New Scientist 2019 May 11; 242(3229): 42-45.

2. Klein, JoAnna. Deep beneath your feet, they live in the octillions. The New York Times 2018 December 19.

3. Purkamo, Lotta. et al. Diversity and functionality of archaeal, bacterial, and fungal communities in deep archaean bedrock. FEMS Microbiology Ecology 2018; 94: 1-14.

4. D'Hondt, Steven; et al. Presence of oxygen and aerobic communities from sea floor to basement in deep-sea sediments. Nature Geoscience 2015; 8: 299-304.

5. Magnabosco, C. et al. The biomass and biodiversity of the continental subsurface. Nature Geoscience 2018 October; 11(10): 707.

6. Puente-Sánchez, Fernando. et al. Viable cyanobacteria in the deep continental subsurface. PNAS 2018 October 16; 115(42): 10702-10707.

7. Windsor, Donald A. Parasitism as a property of life. 2013 September 3. Post #2.

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

9. Windsor, Donald A. Role of parasites in Earth's biosphere. 2017 September 30. Post #13.

10. Windsor, Donald A. Parasitism on Mars. 2015 November 8. Post #10

Wednesday, February 13, 2019


Host Suicide Induced by Parasites Hemlock Woolly Adelgid
Post #26
Donald A. Windsor

Suicide induced in animal hosts by animal parasites has been known for decades (1).

But suicide induced in plant hosts by animal parasites is new to me. The Hemlock Woolly Adelgid (HWA) (Adelges tsugae, Hemiptera) is currently invading Chenango County in central upstate New York, where I live (2). At a training session by the NY State Department of Conservation in Sherburne on 19 January 2019, I learned that the crawler stage of the adelgid inserts its feeding tubes into the stems of Eastern Hemlock (Tsuga canadensis) trees, just proximal to a needle and then feeds on tree sap for the rest of its life. However, this parasite does not kill its host tree. The tree kills itself by shutting off the flow of sap. This defensive reaction eventually kills all of its needles and twigs, resulting in the death of the entire tree, in about 4 years. This suicidal outcome seems to be an overreaction by the host's defense mechanism (3, 4).

The Western Hemlock (Tsuga heterophylla) is also parasitized by a lineage of HWA, but its similar defense reaction is muted enough so that infestations are not lethal (5).

A comprehensive recent review of HWA is provided by Limbu et al. (6).

All of which makes me wonder. When a person has a fatal allergic reaction to a bee sting or a peanut, is that really a suicide? Not in the sense that humans have a free will and killing oneself has to be intended to qualify as suicide. However, the body, sans mind, does indeed commit suicide.

Host suicide may confer a selective advantage if it gets rid of, or retards, its parasite. Consider the interactions of the fungus causing anther-smut disease in several species of alpine carnations (7).

References cited:

1. Trail, Deborah R. Smith. Behavioral interactions between parasites and hosts: Host suicide and the evolution of complex life cycles. The American Naturalist 1980 July; 116(1): 77-91.

2. Anon. Early detection of the Hemlock Woolly Adelgid (Adelges tsugae) in small northeastern hemlock (Tsuga canadensis) woodlots. Forest Connect Fact Sheet, Cornell University Cooperative Extension. 4 pages.

3. Radville, Laura, et al. Variation in plant defense against invasive herbivores: Evidence for a hypersensitive response in Eastern Hemlocks (Tsuga canadensis). Journal of Chemical Ecology 2011 June; 37(6): 592-597.

4. Gonda-King, Liahna ; et al. Tree responses to an invasive sap-feeding insect. Plant Ecology 2014 March; 215(3): 297-304.

5. Foley, Jeremiah R. ; Salom, Scott ; Minteer, Carey.

6. Limbu, S. ; Keena, M.A. ; Whitmore, M.C. Hemlock Wooly Adelgid (Hemiptera:Adelgidae): a non-native pest of hemlocks in Eastern North America. Journal of Integrated Pest Management 2018; 9(1): 27:1-16.

7. Bruns, Emily L. ; Antonovics, Janis ; Hood, Michael. Is there a disease-free halo at species range-limits? The codistribution of anther-smut disease and its host species. Journal of Ecology 2019; 107: 1-11.