This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Hello everyone, and welcome again to The Ocelloid! The intro post before was a little too formal and impersonal, I think, at least for my usual style anyway. So I'm going to overcompensate a little this time - mostly because I'm actually away at a large protistology conference as we speak (yay!), and between all the talks, sciencey things and
drinking networking, there is already hardly enough time to get any sleep, let alone working on things. However, the societies in charge (International Society of Protistologists and Phycological Society of America) have kindly allowed and supported live tweeting (and subsequent blogging) of the conference, which you can follow either via my twitter feed (@ocelloid) or by the hashtag #isop11.
However, before following an obscure conference, you might find yourself wondering - what are protists in the first place? The intro post gives an overview of their importance and phylogenetic position, but might still be vague on what they are in lay terms, without excessive phylogenies. Or why they're such a strange group in the first place. This calls for a very brief sketch of some history of the field (that has many fascinating tidbits here and there, which I'll try to incorporate here and there).
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In many societies, if not most, people tend to fundamentally classify the living world into things that move and those that don't. Things that move are roughly 'animals', things that stand around are 'plants'. The latter also tend to be green, making things quite convenient. Mushrooms, due to not being green and tasting very differently, are weird plants. For most of our existence, this system worked perfectly fine, and still does for most people. Few are foolish enough to venture further.
Things got a little confusing when van Leeuwenhoek devised his own microscope design (single spherical glass lens) and fathered microbiology with it. He looked at pond water, among other things (notoriously, including his own feces) and discovered a whole new world of things that in some very loose ways resembled normal 'terrestrial' life, but were still unbelievable. Prior to van Leeuwenhoek's discoveries, a life as a single cell was inconceivable (of course, few knew about cells at that point either). The microbes were called "animalcules", a cute-sounding name itself based on the plant-animal dichotomy. The motile and predatory microbes like ciliates were deemed to be clearly animals, while the green sessile creatures were micro-plants. Of course, things get funny when you run into the swaths of algal diversity that are flagellated and very motile, and often predatory. Things get funnier yet when you have weird secondary and tertiary acquisitions (endosymbioses) of photosynthesis, and phenomena like chloroplast (plastid) theft. But they didn't know that yet. All they saw was a world for which there was no folk biological prerequisite. Our folk biology is exclusively macrobial.
Interestingly, this taxonomic mess persists to this day in the naming system of eukaryotes. We have two nomenclature codes - one for botany (ICBN) - including fungi - and another for zoology (ICZN). While most taxonomists are (or should be) aware of the vast world outside plants and animals, this strong relic of our folk biology persists to this day, resulting in total chaos with groups like Euglenids - clearly motile and often predatory, but many members very green and algal in the meantime. Yes, this means Euglenid taxonomy falls under BOTH codes, leading to sets of two slightly different names and ranks for each taxon. We like to think of modern science as this super objective activity devoid of historical contingency and human factors, as something that transcends cultural backgrounds. Yes, the scientific method is wonderful, probably the best system for gradually acquiring higher and higher accuracy of predictions, but I like to point out from time to time that science remains (and always will be) a human activity, with all the quirks that come along with that.
I digress. A century and a bit after van Leeuwenhoek's work came Haeckel, and established the kingdom Protista. By then it was becoming clear that the plant-animal dichotomy does not work, nor does the plant-animal-fungal system that came after (of which we still see relics everywhere). The microbes were clearly a separate 'thing' taxonomically, or in other words, things make a lot more sense if you treat them as such. Protista was a kingdom for creatures that defied the animal-plant-fungal classification, which remains the case to this day. Of course, the boundaries and definitions are sometimes vague and disputable, as expected of a group that is defined by exclusion. But apart from the clear distinction between prokaryotic and eukaryotic microbes that arose with the sophistication of ultrastructure (fine cell structure) studies, the kingdoms remain the same to this day.
What is somewhat worrisome to me is the ever-growing gap between the contemporary work of the phylogenetics community (researchers who look at evolutionary relationships between organisms) and the worldview of those outside the field, including that of other scientists. While one small group -- many of whom are at this conference right now -- is developing a more and more accurate and sophisticated picture of microbial relationships, the rest of the world still lives in Haeckel's time at best.
Curiously, you may have noticed above that at this conference we have two societies meeting - the protistologists and the phycologists. You may perhaps recall from the tree and brief discussion in the introductory post before that algae are...protists. So why two societies, especially since the phycologists are, by defintion, a subset of protistologists who study photosynthesising things (especially macroscopic photosynthesising things like seaweeds). ISOP (Int'l Soc of Protistologists) actually used to stand for Int'l Soc of Protozoologists - yes, protozoology as the counterpart to phycology (study of 'protophytes'). The deep folk biological split between non-motile green things and motile non-green things persists even in the organisation of our scientific societies and conferences full of experts who definitely know better. Tradition is strong, and science is still a human activity.
So I hope this clears up a bit on at least why there's a total clusterfuck regarding the term 'protist'. To make things better, we don't have a total consensus on a definition of 'protist' even in the field. I use the word differently from other people here. Some people exclude macrobial (large) things, some exclude green and red algae as well, etc. My definition -- the one that really matters since I run the show here ;-) -- is that a protist is anything that is a) eukaryotic; and b) not an animal (defined by shared origin of multicellularity, including sponges of course), land plant (embryophytes - green 'algae' that produce some sort of embryo tissue and are largely terrestrial) or fungus (defined by...let's not go there today, but roughly speaking, chitinous walls and presence of a dikaryotic life cycle stage, which I believe is in at least most of them). Later we can talk about phylogenetic vs. taxonomic definitions, paraphyletic groups, etc. But for now, have a random video of an amazing pseudopodial network of a naked freshwater foraminiferan: (description in YouTube link)
https://www.youtube.com/watch?v=V_xlx05FVDQ&hd=1
Will definitely explain this organism a lot more later, but keep in mind that this video is in real time, and the movement of particles in that pseudopodial network is unusually fast for a cell. Foraminiferans have a trick for this, and it's really incredible for anyone interested in how cells work. As an aside, some of these buggers can hold down a small animal (eg copepod, brine shrimp) and devour it from within. So much for the common sense idea that multicellular things eat unicellular things, no exceptions.
I will get back soon, with lots and lots of goodies from this protistology conference, which is so far absolutely amazing. As obscure as our field may seem, there are at least a couple hundred of us in it - almost a crowd, if you will. It is wonderful to be around people who share you interests, but even more so when your interests are so odd and arcane.
Until next time (where I will produce a proper post with pictures and references). For now, feel free to follow the conference twitter feed!