Sunday, November 8, 2015


Post #10

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.

Monday, October 19, 2015


Quantitating Role of Parasites in Ecosystems Using Energy Flow

Donald A. Windsor

The work of Hatton et al. may have far broader implications than perhaps the authors and even their reviewer, Cebrian, realize. I suspect that their power law might reflect the important role that parasites play in ecosystems.

Hatton et al. report a predator-prey power law that applies across all ecosystems. Cebrian asks the critical question, “Where does this sublinear pattern stem from?”

I respond that it stems from the underlying actions of parasites. When predator-prey interactions depart too far from equilibrium, diseases take over, which is why our biosphere is so biodiverse. Monocultures are prevented by parasites. Parasites apparently maintain the predator-prey equilibrium at k = 0.75 by accounting for the other 0.25, which would make it linear.

Parasites have been considered as predators since at least 1927 (Elton). The difficulty is that parasite biomass is probably not comparable with free-living predator biomass. Besides, how to measure it would be another problem. It was unintentionally included in the biomasses measured by Hatton et al., which might also be an unrecognized problem. Effects of parasites per unit of their biomass would depend on their potency.

Parasites cannot be ignored in ecosystems, because they outnumber the free-living species that host them. Most of the species on Earth are parasites (Windsor). Why have parasites been so successful throughout evolution? Why have host species not been able to win the host-parasite arms race? My answer is because they are such an integral component of ecosystems that without them ecosystems would not have survived. It is as if hosts and ecosystems are addicted to parasites, at the species level.

The insidious, pervasive ubiquity of parasites renders it difficult to test my hypothesis because it is impractical to make field observations in parasite-free situations. Consequently, I am glad to see approaches, such as that of Hatton et al., which might be used indirectly.

References cited:

Cebrian, Just. Energy flows in ecosystems. Relationships between predator and prey biomass are remarkably similar indifferent ecosystems. Science 2015 September 4; 349(6252): 1053-1054.

Elton, Charles. Parasites. In: Animal Ecology. New York, NY: Macmillan. 1927. Pages 71-82.

Hatton, Ian A. ; McCann, Kevin S. ; Fryxell, John M. ; Davies, T. Jonathan ; Smerlak, Matteo ; Sinclair, Anthony R.E. ; Loreau, Michel. Thepredator-prey power law: biomass scaling across terrestrial and aquatic biomes. Science 2015 September 4; 349(6252): 1070.

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

This article was posted as a comment to the Cebrian article on 7 October 2015. Link is:  


Saturday, September 12, 2015


Post #8

Donald A. Windsor

My working life as a scientist in a pharmaceutical research and development facility was satisfactory. It provided steady employment from graduate school to retirement. The work was interesting, exciting, personally fulfilling, and it paid well. Moreover, I was contributing to curing a great many patients.
But my greatest thrill as a scientist occurred in my life after working, during retirement.

For my doctorate I studied parasites and was fascinated by their insidious involvement in ecosystems. However, to land a job, I had to abandon parasites and adapt my biological and chemical education to medical applications. Upon retirement, I wondered what was going on in parasitology during the three decades I was absent. So I undertook a massive reading of thirty years of parasitology literature. It took me a year and a half. Toward the end I was struck with a eureka moment when it became obvious to me that parasites were not just pesky bit-players. On the contrary, parasites were the prime controllers of ecosystems.

Our biosphere is not free-living organisms parasitized by a few nasty villains. It was the other way around. Our biosphere is composed of parasites that cultivate their hosts, with the parasite species outnumbering the host species. Parasites form an intricate network within the host species that most biologists study. This discovery is even more astounding when considering that most biologists have never even taken a single course in parasitology!

Moreover, parasitism is just one type of symbiosis. Include all symbiosis and the model of our biosphere becomes a mind boggling nexus of different species interacting and evolving together.
However thrilling my discovery was to me, it had no discernible impact on the field of biology. I could not get my ideas published. My greatest discovery, the biocartel, remains only self published. A biocartel is a duel aspect assemblage of all the parasite species hosted by one free-living species or all the free-living species burdened by one parasite species. Disappointed but undaunted, I tried to communicate the basic concepts in very terse letters to editors. I did get one opportunity to express my ideas in the article cited below. It languished for over a decade before it started to get cited. It is now being cited almost monthly.

I am now 81 years old and doubt that I will still be alive when the full importance of parasites is eventually realized. Nevertheless, my case history illustrates two different aspects of a scientist's life, professional employment and personal discovery. Nice if you can get them combined, but to those scientists who cannot, I suggest turning your retirements into new careers by pursuing those aspirational ideas you had back in graduate school.

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