Reading the amazing news about INat’s reaching 500,000 of the 2M described species, I was reminded of something I read in E.O. Wilson’s book “Naturalist.”
Micro-organisms reproduce much more quickly than larger ones, and so evolve and speciate much more quickly. Moreover, the vast majority cannot survive more than a few seconds outside their habitat, and so can’t be isolated and studied. We only know things about a few ultra-hardy microbes.
Beyond that, many of the habitats in which micro-organisms thrive are inaccessible: geothermal vents, the guts of animals, kilometers below the surface of the earth, etc.
The upshot is that biodiversity at the microscopic level is wildly greater than biodiversity that is visible to the naked eye, and the amount we know about it is a tiny fraction of what remains to be learned.
A further implication: there will be work for INaturalists to do for centuries to come.
I don’t personally know how the diversity of microorganisms compares with that of macro-organisms. I did a quick search and found this paper discussing “operational taxonomic units” and “species clusters” in bacteria, with the largest survey to date finding 5.6 million OTUs. However I don’t know how that maps onto conventional taxonomy and presumably most of those species are undescribed. It reminds me of this paper estimating that there are 10x more gall midge species than previously expected, also presumably mostly undescribed.
Also I feel like bacteria don’t really fit well with iNaturalist documentation, even other microscopic organisms like diatoms, rotifers, protozoans etc. which are challenging enough on their own are still identifiable to some extent using photography. You might be interested in this recent thread on microorganisms on iNat: How big is the microorganism/microbiology community on iNat?
Amazing! Thank you so much!! I realize that it will probably difficult for amateur naturalists to observe microorganisms. But if you look at the way phone camera technology has advanced in the past fifteen years, it wouldn’t surprise me of some cheap and powerful microscopes become commercially available in the next ten to fifteen.
In “Naturalist,” Wilson said if he’d had his career to do over again, he would have studied micro-organisms rather than ants. I love ants and all macro-biota. But Wilson’s comment opened my eyes to the richness of the microsphere. My forecast is that INaturalist and its users will cover more if it in the years to come.
Thanks again! I’ll check out those links right now.
I guess the terms you’d use to distinguish these categories are eukaryotic microorganisms and prokaryotic microorganisms. Are prokaryotes generally identifiable with microscopes or do you need to run chemical or DNA tests on them?
I found this paper estimating only 200,000-250,000 total species for eukaryotic microorganisms, which seems very low to me. Like compare that number with the number of beetles (400k described, estimated 1-2 million total).
That does sound low to me. I read a thing by Stephen Jay Gould on the abundance of microscopic life underground, much of it thriving at shocking depths. His estimate was that, if all subterranean microorganisms were brought to the surface, they’d cover the globe, oceans included, in a layer five feet deep. Only a minuscule fraction of those organisms have been studied.
This was in the nineties, so estimates may have changed. But 200k species sounds very low indeed to my non-expert eyes.
I had a discussion with Dr. Wilson on this over three decades ago, as I sought to take a postdoc in his lab-- he felt I was overqualified, an electronic microscopist and protein chemist, working on a human parasite, tracking evolution through continental drift over 68 MYA! And I countered with the fact that macrostructure was the tip of the iceberg, and if we could fix organisms in place and then do our studies at the ultrastructural and molecular level, the further understanding was endless.
He was nearing retirement, winding down his lab, and this was too great a leap. But mind you, actin is the answer: its gene is conserved almost since the first organism coalesced. When Wilson wrote this, we were developing all kinds of microscopic and ultramicroscopic tests, like ELISA at the ultrastructural level, tracking specific protein locations within the cell.
I find no aspect in what Wilson says here wrong. More folk could benefit from reading Lewis Thomas’ Lives of a Cell , and become awestruck at how many details we still don’t know, but just need to look at.
Amazing stuff! What a remarkable man, and what a career he had. I teach history, but if I had it all to do over again I think I would have gone into some Wilson-influenced biological field. I’ve read most of Wilson’s more popular books and a couple of his more technical ones. I’ll definitely read Thomas, thanks to your suggestion. The microscopic world is a fascinating universe. I hope it becomes a bigger part of INaturalist in the future. Thanks so much!!
Probably not, sadly. Optics are a very mature field (compared to consumer electronics) and interest in microscopes is comparably low, so it wouldn’t make sense, economically, to invest all the money into manufacturing technology to make them cheaper when universities and research labs are happy to pay current prices.
Even with the best microscopes, most prokaryotes stay very hard to identify. At that small scale, there’s simply a limited amount of shapes you can have. If you are lucky, you’d at least need colony morphology, reaction to some stains (gram stain, for example) and other chemicals, behaviour under different microscopic settings (phase contrast, fluorescent, etc.), and/or information on metabolical pathways, but for many you need genome analysis for species level ID.
Interesting! You may be right about the microscope situation, but I just tried the Iphone 16 pro max, and checked out its “magnify” function, which was astonishing, and a good deal more powerful than my IPhone 13. I wouldn’t be surprised by incremental improvements that will aid in the observation of very small, if not microscopic organisms–mites, tardigrades and the like.
As for prokaryotes, I am totally in the dark! Thanks so much for the wonderful info!!
Well, much improvement in phone cameras comes from the sensors, software stuff, and the shrinking of other components allowing for more space for optical elements, rather than the lenses themselves. As microscopes themselves do not come with a sensor, there is no real improvement there. Secondly, microscopes operate far closer to the actual physical limits of what can be achieved than phone cameras. There is only so much optical magnification you can get. You will struggle to get good light microscopy images of E. coli now, in 10 years, and in 1000 years.
And like I said, there is a much larger financial incentive to upgrade phone cameras than “consumer microscopes”. I guess we will see better and better microscopes enter the second hand market though, as they get phased out in unis and labs.
Stephen Jay Gould referred to “the modal bacter.” In context, he was trying to say that our notions of evolutionary “progress” are unfounded; that “increasing complexity” is not the trend of evolution but merely a consequence of a lower bound to complexity.
To put it in as simple terms as I can (Gould wrote a whole book about it): if you start with an organism and allow subsequent generations to vary randomly, all else being equal, they are equally likely to become less complex as more complex. If there were no barriers, you would expect to see a bell curve of complexity, with most organisms in the middle and few at the extremes. However, given that the starting organism was a prokaryote, there is a lower bound – it is not possible to get much less complex; whereas there is no known upper bound. Thus, the actual situation is a skewed bell curve, where at any given point in evolution, most taxa are prokaryotes and what looks like “progress” is just expansion of variation in the only possible direction.
But if I read you correctly, you are addressing the issue of complexity, not diversity. As life has diversified, it has not become uniformly more complex, as you elegantly express above. But it has become more diverse.
My interest is in the diversity piece: my hypothesis is that microorganisms are more biodiverse than macro-organisms.
And, to your point, the diversity of microorganisms comprises more and less complex species.