I want to talk about two basic issues in this essay: 1)
scientific names and 2) taxonomy or classification systems. Strongylocentrotus
drobachiensis is the name of a green sea urchin. It's not a
very big animal and even including the spines, it ordinarily
isn't more than 6 inches in diameter. I once read that this is
the longest scientific name for any organism. Whether this is
true or not, I hesitate to mention it for fear that it might
prompt a contest among biologists to come up with longer and
longer names. Reputedly, there is an annual contest in Germany to
come up with the longest compound noun which makes sense. Years
ago, one of my German professors reported that one of the
(a cheese made in a monastery as a breakfast delicacy for the
Passion Play at Oberammergau). So, this is clearly not a trend
that one would wish to encourage in biologists and perhaps
particularly not in German biologists.
Spirostomum ambiguum is a protist which rarely exceeds 2 millimeters in length. Perhaps there ought to be a rule that the size of an organism should play a role in the length of the name. One suspects that at one time bacteriologists must have had been plagued with a sense of mediocrity since they were studying some of the smallest organisms and yet they invented some of the longest names. When they find some nasty pathogen, this seems to bring out their nomenclatural worst. Consider Staphylococcus hemorrhagicus, Streptococcus erysipelatis, and Plasmodium cathemerium. But invertebrate biologists are no better regarding such matters. A small flatworm has the intimidating name of Rhynchomesostoma rostrata which it carries around on its 5 millimeter back. An even smaller flatworm bears the hefty moniker Geocentrophora sphyrocephala! And then there's a rotifer only 350 microns long called Wierzejskiella ricciaeI dare you to say that fast ten times. And, if you're interested in copepods, you'll certainly want to be able to distinguish between Maraenobiotus insignipes and Ergasilus centrarchidarum which ought to be easy since Ergasilus is parasitic on the gill filaments of fish, but only if it's in its adult stage and only if it's female. Even plants don't escape these nomenclatural abuses; there is a vascular freshwater plant with the lilting name of Myriophyllum alterniflorum. Having taught university students for 35 years and having observed the decline in their vocabularies and abilities to use language properly, I have often urged a return to the old-fashioned curriculum that requires Latin and Greek. However, whenever I think about the linguistic excess of taxonomists, I'm not so sure that, after all, that is such a good idea.
Ostensibly, scientific names were once designed to be descriptive.
Certainly the name Chaos chaos for the giant amoeba is distinctive and descriptive. Spirostomum ambiguum is descriptive in part: "the one who is spiral-mouthed and is ambiguous". Well, I don't know quite what's ambiguous about this particular organism as contrasted with a whole lot of other beasties, but, perhaps, whoever named it really meant to indicate that it is mysterious, in which case its name is ambiguous and it probably should have been called Spirostomum mysterium.
One might ask why we don't just follow the simple procedure of giving descriptive names in our native language. After all, if the Catholic Church could go from the Latin mass to the mass in English, Urdu, Swahili, Japanese, etc., then why not do something parallel for scientific names? Well, the answer's obvious, isn't it? We'd come up with something like "micro-whale" for Spirostomum and the Germans would launch "das Zirkelmundbandformiggrünblauigsüsswasserkleintierchen" for the same little beastie and win a prize in the annual contest. Sometimes there are very good reasons for standardization. Nonetheless, the biological nomenclaturalists could be more considerate.
A major problem for the microscopist is that few of the organisms in which we are interested have common names. Bird watchers can talk about cardinals and orioles and nuthatches and magpies and gimlet-eyed tidwatchers (sorry, sometimes I like to make up names myself) or fish enthusiasts speak of betas and angelfish and neon tetras, whereas we are left in the situation of enthusing over spine cross sections of Strongylocentrotus drobachiensis, which, by the way, are quite splendid.
We humans like to know where things fit and so we invent classification systems. So, the microscopist can say, protozoa are animals and algae are plantsright? Well, no not anymore. I recall a children's game called Twenty Questions. One person thought of an object and the others could ask twenty questions that could be answered yes or no in order to try to guess the object. The one who thought up the object had to tell the others if the object was animal, vegetable, or mineral. These were simpler, although not necessarily better, times. I suspect that botanists used to feel inferior, like second cousins, because generally speaking, trees are not particularly dramaticthey don't run or jump, swing or growlalthough there are "weeping" willows. So when something as exciting as Volvox comes along and it's got chlorophyll, well, naturally the botanists want to stake a claim to this magnificent organism. But the zoologists had their aesthetic sensibilities finely honed too, and pointed out harshly, that plants don't swim, and so, the famous chlorophyll vs. swimming debate began. As a consequence a lot of rhetoric was flown high and a lot of ink spilled.
Then in the last decade or two, some biologists decided to try to resolve some of these difficulties, and as is usually the case with such compromises, made things much more complicated and created a whole new set of conflicts and debates, some of which are so heated that certain biologists are barely on shouting terms. Whereas previously we had just three major categoriesanimal, vegetable, and everything elsewe now have six: monera, fungi, protista, animal, plant, and everything else. However, some people don't like the name "protist" which comes from the 19th Century German biologist, Ernst Haeckel, and have proposed instead the term "protoctista"what an ugly word! At the very least, it should be protictoctista (pro-tic-toc-tista). A word to biologists: Watch your language! Many of the old terms were descriptive and evocativeStentor is good; it looks like a trumpetLacrymaria olor, "tear of a swan" is poetic, but Strongylocentrotus drobachiensis for some wonderfully spiny little urchincome on! And "Protoctista" is a first-rate abomination. However, whether you refer to this kingdom by Protoctista or Protista, it's one of the most motley collections of organisms imaginable. Browse in the Handbook of Protoctista and you'll encounter beasties that are stranger than anything in science fiction. Protist is a Humpty-dumping-ground category; if the object in question doesn't fall into the monera, fungi, animal, plant, or everything else categories, then it clearly belongs to the kingdom Protista.
In the Handbook of Protoctista, there are listed 79 classes under 35 phyla, although the two classes in the last phylum are of rather uncertain status due to a paucity of information.
The phyla are then put under 4 major headings with a fifth for those last two classes:
I. NO UNDULIPODIA; COMPLEX SEXUAL CYCLES ABSENT
II. NO UNDULIPODIA; COMPLEX SEXUAL CYCLES PRESENT
III. REVERSIBLE FORMATION OF UNDULIPODIA; COMPLEX SEXUAL CYCLES ABSENT
IV. REVERSIBLE FORMATION OF UNDULIPODIA; COMPLEX SEXUAL CYCLES PRESENT
V. INSERTAE SEDIS
(from pp. xiii-xiv)
SEX, SEX, SEX, SEX. That's all these biologists seem to have
on their minds. As Elsa Maxwell once said: "Too many people
have sex on the brainand that's no place for it." But
before we get to the good stuff, we need to talk about this bit
of jargon "undulipodia" or "little waving
foot"sounds rather like a parody of an American Indian
name, doesn't it?
The senior editor, Lynn Margulis' first two sentences under the heading of "Terminology" are: "The senior editors and contributors nearly came to blows concerning aspects of terminology. We are dealing with the collapse of the walled structures of academic disciplines such as protozoology." (p. xii) Undulopodia is the term which Margulis wants to substitute for cilia and flagella (which are "nearly" identical) in eukaryotes. The application of the term flagella would then be restricted to "extracellular", "intrinsically nonmotile" organelles of prokaryotes. Confused? It gets worse. "Mastigote" is now to be the new term for the "traditional flagellates".
And this is only the beginning. It get's really quite interesting. For a very long time, protozoa have been described as single-celled animals. However, some recent biological taxonomists have tried to move away from that description by creating an entirely new kingdom for a large set of groups of organisms that have never quite comfortably fit into the traditional plant-animal distinction, in other words, the Protista, which we have been talking about. One of the virtues of this approach is that it obviates the long-standing dispute regarding whether certain organisms, such as chlorophyll-bearing flagellates are plants or animals. Historically, some of these organisms have been vigorously claimed by the botanists and equally passionately claimed by the zoologists. Some of these disputes have had the intensity of the medieval theological debates over the categories of Being which led to street fights between monks. Isn't that a provocative image! As one might expect, this new approach to classification has not resolved all of the problems. The publication in 1990 of the Handbook of Protoctista involved four chief editors and over 60 major contributors world-wide. In the introduction to this volume, Lynn Margulis states: "Even today, many scientists (e.g., especially cell biologists, plankton ecologists and geologists) routinely write about Protozoa and Algae as if they were phyla in the Animal and Plant kingdoms, respectively. These organisms are no more 'one-celled animals and one-celled plants' than people are shell-less multicellular amebas." This is a radical challenge to a long-established tradition, but one which is supported by many very eminent scientists. However, this general agreement still produces some significant differences of opinion about both classification models and terminology.
As we mentioned above, one particularly intense battle centered over the attempt to replace the words "cilia" and "flagella" with the term "undulipodia." Somehow I find it rather comforting that scientists as well as philosophers can still get so passionate about such arcane matters that have so little to do with a practical world in which most of the people have never even heard of, let alone observed, a cilium.
The more I have studied micro-organisms, the more sympathy I have developed for the view that denies saying that protozoa can be accurately described as "one-celled animals," but the less patience I have for the excesses of overzealous taxonomists.
One thing that becomes clear rather quickly is that the four major groupings listed above (using the criteria of undulipodia and sexual cycles) are arbitrary. They may turn out to have a high degree of utility and so become standardized until the next taxonomic "revolution," but we always need to remind ourselves that these are human inventions for our own convenience. As a boy of 15, I was much taken with taxonomy and used to make elaborate charts tracing the evolution of invertebrates. They were, of course, naive, but they did help me understand certain problems and I came to think of taxonomy as a way of clarifying the relationships between organisms. Not any more!
There is a dilemma regarding this kingdom of Protista. Remember those wonderful 19th Century volumes which had incredibly long explanatory subtitleswell, that's true for the Handbook of Protoctista as well. Sometimes old habits die hard. Here is the full subtitle, "The Structure, Cultivation, Habitats, And Life Histories Of The Eukaryotic Microorganisms And Their Descendants Exclusive Of Animals, Plants, And Fungi: A guide to the algae, ciliates, foraminifera, sporozoa, water molds, slime molds and the other protoctists." This sounds like a parody of a Victorian tome on Natural History, but, go look, and you'll find I didn't make any of it up; it's all there and an ambitious subtitle it is too.
There is a lot going on in this subtitle. Note that it excludes fungi, but includes water molds and slime molds, so you can bet that if Dr. Margulis had her way, we would see some even more radical terminological surgery. Just think what's being said here: we have molds that aren't fungi; algae that aren't plants; ciliates, foraminifera, and amoebae that aren't animals! Some of these protists are freshwater, some are marine, some are estuarine, some are terrestrial, some live on snow banks, some live in thermal pools, some are parasitic, and some can survive for decades in cysts. They range in size from organisms that measure slightly less than 1 micron to the giant kelps that can exceed 100 meters. There are creatures here, like the sporozoans, that generally lack anything that we would readily identify as behavior to ciliates like Urocentrum turbo which are absolute dynamos whipping through the water at breakneck speeds. One could go on and on about the differences, but the real issue is: what do all of these diverse organisms have "in common"? In the introduction to the handbook, Margulis admits the following: "Unfortunately no neat definition encompasses all the protoctistan diversity, except a definition by exclusion." (p. xvi)
As weak as this sounds, it really shouldn't surprise us too much. The world is an exceptionally complex place and sometimes we tend to forget that and trying to put things in order to help us understand these complexities is no easy task. We have to devise methods of grouping things in ways that are useful. Imagine a system in which we classified everything according to color. We would, of course, have to have specialists and soon the specialists on things "red" would be involved in heated disputes with specialists on things "orange" and on and on. To what point? There generally isn't any utility in classifying things according to color.
So, when thinking about classifying things, we have to think about utility and also recognize that such systems are going to get more and more complicated as we learn more and more about the things we want to classify. We also have to learn to ask the right questions. I used the phrase "in common" a bit ago and this has been one of the major difficulties about classification schemes and it is a difficulty which we inherited from Plato and Aristotle. Early philosopher-scientists were looking for a neat system of definitions which would be expressed as a series of criteria stating the essence of what something is. For example, Plato once defined man as "a featherless biped." Diogenes of Sinope, the Cynic, plucked a chicken, walked into Plato's lecture room, held it up and said: "Here is Plato's man." So, you can see that difficulties about classification have a long history.
But back to the issue of "in common". We might ask what a Paramecium has "in common" with a giant kelp that allows us to classify both as protists? May I have the envelope, please! The answer is: nothing. Well, nothing very useful anyway. We can say that they're both alive but so are plants, animals, and fungi and Dr. Margulis certainly won't let us use that as a criterion for sneaking those into the Kingdom of Heavenly Protoctists. They both live in water. Well, so do whales. Clearly, we need a different sort of approach.
The philosopher Wittgenstein came up with a notion called "family resemblance" which might be helpful in understanding some things about classification. However, take notethis idea has nothing to do with the fact that you may look very much like your brother, especially if you're identical twins. Rather than looking for a set of criteria which groups of things have in common, we instead look for shared or connected criteria which allow us to assert a relationship. This sounds rather murky, but the basic idea is quite straightforward. Below is a greatly over simplified example, but it will serve to illustrate the essential point.
Notice that organism #7 has no criteria in common with numbers 1,2, or 3. However, it does have one criterion with #4, two criteria with #5, and three criteria with #6. Note further that numbers 4,5, and 6 do share criteria with numbers 1,2, and 3. The shared criteria become more evident if we draw some diagonals in our diagram.
When one considers that there may be hundreds, even thousands, of criteria involved in the classification of an organism, then one begins to appreciate the difficulty of the task. The kingdom Protista (or Protoctista) is a stop gap measure. As we learn more about these organisms and discover yet new ones, categories and criteria will change. We need to remind ourselves that there are tens of thousands of organisms which we have yet to discover. In the meantime, the protists are a wondrously bizarre collection of organisms that challenge us and remind us that the basic sense of astonishment at the variety of nature is the foundation of both philosophy and science.
Whoops! We forgot the stuff about sex. It's probably just as well. Sex in protists is far too complicated and interesting to gloss over in just a few paragraphs, so I promise I'll devote a future essay to this topic.
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Published in the June 1999 edition of Micscape Magazine.
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