Notes from dreamworlds
March 27, 2012 4:53 AM   Subscribe

Microworlds is the blog of biology student Daniel Stoupin, and he also has a photography website as well. His chosen subject is microphotography, especially of living things. Perhaps the best place to start is his latest post, where he uses fluorescent dyes to take pictures of a rotting flea embryo. Other favorites are shells of microscopic crustaceans, colorful plant seed fluorescence and mosquito larva in polarized light. He has also made a video, and explains the process here.
posted by Kattullus (15 comments total) 22 users marked this as a favorite

One of my biology teachers once asked us to guess the average size of lifeforms on Earth.

We were surprised.
posted by Trurl at 5:47 AM on March 27, 2012 [2 favorites]

Gah, this interface again that is unusable on iPhones.
posted by oneironaut at 6:41 AM on March 27, 2012

posted by ColdChef at 6:41 AM on March 27, 2012

Averaged across species or across individuals, Trurl? It'd be very small either way but if it was only across species I bet it'd still be macroscopic. I think it's somewhere around honeybee size actually...faint bells are ringing. Across individuals it'd be swamped out by bacteria of course.

Did you know that the bacteria living in and on your body outnumber your own cells by a factor of ten to one?

Did you know that approximately 1/4 of all species on this planet (unicellular species included) are beetles?

This is great.
posted by Scientist at 7:05 AM on March 27, 2012 [1 favorite]

No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinised and studied, perhaps almost as narrowly as a man with a microscope might scrutinise the transient creatures that swarm and multiply in a drop of water.
posted by seanmpuckett at 7:15 AM on March 27, 2012 [1 favorite]

If you like this, I recommend the posthumously published Micro by Michael Crichton- a horror story on this scale
posted by MangyCarface at 7:18 AM on March 27, 2012

"Do we really see the life around us?" Answer: I'd rather not, yergh.

(No but that's really cool that we can do that. And water bears are cute.)
posted by Mooseli at 7:34 AM on March 27, 2012 [1 favorite]

Averaged across species or across individuals, Trurl? It'd be very small either way but if it was only across species I bet it'd still be macroscopic. I think it's somewhere around honeybee size actually...faint bells are ringing. Across individuals it'd be swamped out by bacteria of course.

I would imagine this is something that is rapidly changing as we discover more microscopic species. And, of course, the notion of species, which is highly ambiguous on a macro-level is even more so on a microscopic level where many organisms are being identified solely based on DNA analysis.
posted by snofoam at 7:49 AM on March 27, 2012 [1 favorite]

Actually, we have decent projections on how many species there ought to be in total based on the number that we've found so far. The basis for this is rarefaction, although for something like the total species richness of the Earth it's quite a bit more complex than the examples you find in textbooks. Still though, people have tried and while I'd bet there's a better-than-even chance we have some surprises in store, we still have some pretty decent guesses. (1.8 to 2.0 million total species, estimated.)

We have pretty good estimates at each level, too. Taxa get shifted around and as you rightly pointed out the number of taxa and the number of sub-taxa in each one is a somewhat subjective thing that varies based on whose theories you subscribe to and what definitions you're using, but we can be reasonably certain about the basic patterns. Here's the best presentation I could find on the number of species per phylum, which should give you a reasonable idea of where the bulk of species diversity is: species per phylum on Wikipedia. I wish I could've found a better chart at a more authoritative source but it's surprisingly annoying to locate.

So anyway, it's not changing all that much. Not as much as you'd think, anyway. I point this out because I found it pretty surprising how much we actually know about this stuff when I was being taught it. It seems like, given how crazy diverse everything is and how impossible it is for anyone or even for everyone to see absolutely everything, that we really shouldn't be able to know this stuff. Yet, through the power of statistics, we do -- not perfectly, but to a useful degree. It was also surprising to me that so many species were actually macroscopic. Not individual organisms, of course, those are almost all microscopic. But at the species level (and yes, definitions of species are fuzzier when you're dealing with asexually reproducing organisms, and yes, species definitions are actually fundamentally arbitrary and only valid to the extent that they are useful) it's actually mostly insects and, yes, a quarter of all species (roughly) are in the order coleoptera, which are beetles.

I know, right?
posted by Scientist at 8:21 AM on March 27, 2012 [2 favorites]

Sure, god was inordinately fond of beetles, but I think there is also some confusion here because the original comment was average size of lifeforms. For animals, I can definitely imagine that the relative magnitude of the different phyla would remain mostly unchanged in the future unless we make big changes in how we classify (versus discovering new critters). For bacteria and stuff, though, I feel like there is much less consensus about the potential number of so-called species.
posted by snofoam at 8:51 AM on March 27, 2012

Well, we definitely don't have as good estimates for bacterial species richness as we do for species richness in eukaryotes (i.e. plants, animals, fungi, anything with a nucleus in in its cells including all multicellular life) and a lot of that is down to the fact that bacteria are relatively difficult to observe (being microscopic) and good species definitions are hard to make (since they reproduce asexually). However, our best estimates (as of this 2006 paper, though to my knowledge there have been no major paradigm-upending breakthroughs since then) put total species counts for bacteria in the 5,000-10,000 range.

This is indeed a bit weird, as it's sort of a rule in the rest of biology that as body size decreases, species richness increases; bacteria of course have the smallest body sizes of all, so it does seem strange that they wouldn't follow this pattern. As of now there's not (to my limited knowledge) great agreement regarding why they don't follow this pattern, and it's certainly possible that the answer will be along the lines of "they do follow it, we were just missing the other 99.9% of bacterial species" (which is about how much we'd have to be missing to make them fit into the body size/species richness curve that we use with plants and animals) but I wouldn't bet on it.

My bet would be a combination of some missing species (mainly in extreme environments that are not well-sampled) a lot of ambiguity about species boundaries (meaning that bacteria just aren't as biologically segregated as eukaryotes, not simply that our definitions are bad) and also general differences between bacteria and multicellular eukaryotes that cause their speciation to be governed by different sets of principles (which are at present not well-understood). There's a ton of space for further study here and it's a very active field. For instance, there are ongoing efforts to perform bacterial soil censuses and other mass-catalogues of bacteria, based on molecular techniques that have only recently become viable.

It's a thriving field of study and one that a lot of people are pouring a lot of effort and thought into. I fully expect that we will learn a great many surprising and wonderful things as the projects that have begun in the last decade begin to bear fruit. Still and all, I'd be very surprised indeed if the bacterial species count increased by the three or more orders of magnitude that would be required for them to dominate global species richness.
posted by Scientist at 9:21 AM on March 27, 2012

I guess I just don't draw the same conclusion, even from the article you linked, which is largely a list of reasons why the 5,000 or so described species is just a drop in the bucket compared to the probable number of species. A lot of estimates I've seen have been north of 10 million potential species.
posted by snofoam at 9:46 AM on March 27, 2012

OK, you know what, you're right. I feel rather foolish. Results are indeed coming back from the new studies and they're showing levels of species diversity that are much more in line with what traditional models would expect.

There are limitations to these studies (they tend to just analyze a bunch of DNA in a soil sample or something and give an estimate of how many different bacterial species it came from -- doesn't tell you much about those species) but they're great for getting at the question of how many bacterial species are out there. Here's one of those studies (PDF) and it mentions species counts for marine soil on the order of thousands per gram.

This page gives a broader overview of the field in general, though it doesn't cite many sources. The one paper it does cite, Estimating Prokaryotic Diversity and Its Limitsby Curtis et al, is from back in 2002 (which is a long time ago for this stuff) but it estimates global bacterial species counts on the order of millions to tens of millions.

That's definitely huge compared to the number of eukaryotic organisms, and I'm annoyed that I was carrying around my misconception about species richness for so long. They don't tell you about this stuff in school, at least not in the courses that I've taken, and it's bloody annoying because 10,000,000 species of bacteria vs. 5,000 is a huge freakin' deal and really helps to put in perspective just how new, and dare I say relatively unimportant macroscopic life is, relatively speaking, as a component of life in general. Honestly one ought to look at the whole domain of Eukarya as just a footnote in the long story of life on Earth, according to this data.

Bloody foolish of me.
posted by Scientist at 10:27 AM on March 27, 2012

I think I know the feeling. When I was a kid and early teenager (i.e., the 1980s), I was really into biology and then didn't really pay attention to it until the last three years or so when I started studying the local fauna after moving to an island. There were a lot of Rip Van Winkel moments for me when I was researching things I once knew. Cladistics was a big one, but there were many others, like finding out termites are cockroaches. I am pretty sure that when I was a kid Orthoptera included mantids and walking sticks, too.
posted by snofoam at 12:09 PM on March 27, 2012 [1 favorite]

His chosen subject is microphotography,...

Microphotographs are photographs shrunk to microscopic scale (for example, microfilm or a spy message contained in a period at the end of a sentence). When you take a regular-size photo through a microscope, it's called a photomicrograph.
According to Wikipedia
posted by exphysicist345 at 3:31 PM on March 27, 2012

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