TODAY I WAS reading about protostomes and deuterostomes, and in the process stumbled across a mention of chaetognaths as deuterostome-like protostomes. Since I had no clue what a chaetognath is, I looked it up and found Wikipedia’s entry, which describes them as “predatory marine worms”. This prompted the question: What is a worm?
I know it may seem shocking, but I haven’t really given much thought to the essence of wormness since General Zoology in college. So since I was already at Wikipedia, it was convenient to look up their article on worms. I found it wasn’t very illuminating. It lists multiple phyla containing “worms”, whimsically wrapping up the list with “Tapeworm {live in humans}”, which just goes to show you should double-check anything you find on Wikipedia. So I did so–and found “worm” really has no practical meaning at all.
This time I decided to go somewhere authoritative, so I jumped over to the Tree of Life’s page on Bilateria. There I see several groups of “worms” as unrooted clades, more “worms” in Lophotrochozoa (including Annelida, which contains the familiar earthworms), and other “worms” in the sister group Ecdysozoa (one being the Priapulida, which upon further research Terry Pratchett would classify as “humorously-shaped ecdysozoans”). It’s clear that many “worms” are not particularly closely related to each other, but at least so far they’re all protostomes. Shall we say a worm is a soft-bodied, elongated, limbless protostome? Just on a hunch I clicked over to expand the deuterostomes, which I found contain more “worms”! Apparently the word “worm” simply means “a squiggly bilaterian”, and thus is about as useful as the word “bug” in the vernacular, where it means “a crawly bilaterian”.
Based upon this research I propose an abolition of the word “worm” as a descriptor of any animal group and its replacement by “vermiform”, or perhaps “worm-like” for a more general audience. Since most people will think of the earthworm as the iconic worm, this terminology should communicate that it’s a squiggly bilaterian without suggesting a close evolutionary relationship of all “worms”.
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February 21, 2008 at 7:51 pm
The Term “Mammal-Like Reptiles” Enrages Me « Nimravid’s Weblog
[...] characters? It’s a mammal-like reptile. Again, we return to my earlier complaint about the sloppy use of the term “worm”–when you use a term so indiscriminately, it ultimately provides no useful information at all. [...]
February 23, 2008 at 12:59 am
Daniel Hornbrook
Since I have two small vertibrate mammals living in my house who have yet to show any inclination toward or interest in Linnaean taxonomy, I oppose the removal of “worm” from the vernacular, although it isn’t particularly useful for classification purposes. These particular individuals expand the definition of “worm” to include anything that looks like it might be shaped like a worm, including parts of the human body, as well as inanimate and inorganic household objects.
Although I can’t find the origin of the word, all Germanic languages include a derivitive of “to worm” as a verb, but English is the only language that includes a similar noun. I suspect that the original definition of a worm is close to “something that worms.” Perhaps my daughters’ definition is close after all!
February 23, 2008 at 10:37 am
Nimravid
Your course is clear–purchase a book on invertebrate zoology and make that bedtime reading. It’s never too early to start! ;-)
I admit at that age my and my sister’s grasp on taxonomy was also poor. However, my mom can tell you that the statement, “There’s a worm in the basement and it hissed at me!”, while inaccurate, is compelling.
May 23, 2008 at 12:53 pm
atrijez
yeah, the word “worm” is like the words “fish” and “insectivore”. it makes some level of sense on a taxonomic level, but not on a cladistic one. it’s basically saying “all of the descendants of a specific common ancestor (in this case, the MRCA of bilaterians, or at the very least, the MRCA of coelomates) that have not changed much in form since the time of the common ancestor (which of course is largely subjective and reflects a lot of ignorance on the part of the people who lived before these last couple of centuries)”.
cladistically speaking, if it can be said that the MRCA of all bilaterians was a worm, then that would mean that all living bilaterians must also be worms (humans included). most people don’t really understand how cladistics works though, so the common definition of “worm” ends up being something more along the lines of “any members of bilateria who haven’t yet evolved out “wormhood” by growing legs and eyes”.
and as counter-scientific as this sounds, there might be some use for a term like “worm”. it would be cladistically incorrect to sooner group a coelacanth with a trout than with a horse, but it might make better physiological sense to group the coelacanth and trout together as “fish” and make the horse the outgroup. after all, if your pet coelacanth were sick, which would you sooner call, a vet who specializes in trout or one who specializes in horses??? and perhaps this same argument could be made for a pet “worm”, whether it be of the form “round”, “flat”, “earth”, or “arrow”.
September 25, 2009 at 9:11 am
martin braun
Re: Worm is a useless word
It appears that in using a general purpose encyclopedia(wikipedia is as general as they get) that your objection to the term “worm” is really an objection to the lack of specificity in the English language.
It is also said that apples, oranges, sausages and people have “skin” . One can skin a cat, skin your knee or give me some skin as well as cover an organism with it.
That is the way language works and without the ability to be highly specific one minute and to make ridiculously broad generalizations the next, we would have an awfully difficult time communicating with one another.