Science Snippets
Sly Little Slime Molds - Episode 2
By Fred Baer
June, 2004
In Episode 1, I had a lengthily discussion with Slim, an acellular, or true, slime mold of my acquaintance. Toward the end of said discussion, Slim had suggested I have a chat with his cellular slime mold relatives because they had “a neat trick.” I said I would do so in Episode 2 that, mercifully, is the last slime mold episode and shorter than Episode 1. (I have finally realized that the Editor does not pay by the word.)
Following Slim’s directions, I moved off through the forest a hundred yards or so and started looking for something that looked like Slim – a thin, branching thingy that looked like clear gelatin that was still a bit runny. None in sight, so I called, “Are there any cellular slime molds in the area?”
From near my foot, a tiny voice, or actually a chorus of voices, said, “Well there’s me or us, depending on how you look at it.”
Surprised, I looked down and saw a tiny, flattish, slug-like creature emerging from the soil. It appeared to be about 1/16th of an inch long.
“My,” I said, “you don’t look like Slim at all.”
“Oh, him. Of course not,” chorused the slug. “Slim is an acellular slime mold plasmodium, that being how he spends most of his existence. We, or I, depending on how you look at it, are cellular slime molds in what biologists call a pseudoplasmodium, something that lasts for less than a day. And while we’re on the subject, we think it’s pretty nervy that biologists say that acellular slime molds are the true slime molds and also say that acellulars have the plasmodium stage whereas we cellulars just have a pseudoplasmodium stage. Pure discrimination. It makes us sound like second class citizens, ones who are trying to fool people as to what we are. I suspect a biologist misidentified us once upon a time and, rather than admit his mistake, blamed the victim.
“You aren’t a biologist, by any chance, are you?”
“Me a biologist. Oh no!” I demurred. “Really, I just came to visit because Slim said that cellular slime molds have some sort of neat trick I should learn about, Mr. – er – Ms. – er – what shall I call you? And are you a ‘you’ singular or a ‘you’ plural? You seem a bit indefinite on the matter.”
“Ah! Well, I haven’t bothered with a name, given the transient nature of this pseudoplasmodium stage, but you can call me – um – Grouper,” chorused the tiny slug. “And the neat trick is the reason for the uncertainty as to whether I am an ‘I’ or a ‘we.’ You see, unlike the acellular slime molds, we cellulars spend most of our time as single, tiny ameba-like cells living in moist soil and downing such goodies as bacteria and various decay products for our meals. If food gets scarce, we do our trick. Single cells join together and form a pseudoplasmodium such as myself. There can be as many as hundreds of thousands of cells in a pseudoplasmodium. And unlike Slim and his kind, the cells do not merge. They sort of glue themselves together but keep their separate identities. That’s why it’s not clear if we are an ‘I’ or a ‘we.’ In any event, once we have formed our collective, the slug acts like a single creature. It travels a short distance and out of the soil to reach an area with food. Once it is there, some of the cells form a stalk and other cells climb the stalk and form spores atop the stalk. The spores scatter and become a new generation of ameba-like cellular slime molds. Sad to say, everything but the spores die.”
Ever one to focus on irrelevancies, I asked, “Did you say ‘collective’?” I was thinking “Commie.”
Grouper reconsidered. “Um, perhaps a ‘voluntary association’ might be a better term,” he allowed. “You know, like on the Great Seal of the United States –‘E Pluribus Unum.’ ‘Out of many, One. ’ ” At which point Grouper brought a tiny American flag out from somewhere and did a choral version of The Star Spangled Banner.
I relaxed a bit and decided that notifying Homeland Security was unnecessary.
“That is a neat trick,” I allowed. “I don’t think anything else can organize itself that way out of individual cells.”
“Well,” mused Grouper, “there are sea sponges. Take one, push it through a fine mesh and it separates into single cells. Put the cells into a container full of seawater, and the cells will reform the sponge. Do the same trick with two sponges from different species, and the cells will reform the two sponges. The right cells go to the right sponge.”
Feeling slightly queasy at the thought of zombie sponges, I told Grouper, “This is fascinating, but I must go before I start a third page.”
Thanking him, I left. As I departed, I thought again of notifying Homeland Security about Grouper’s “collective” comment. Consider the legal questions that would be raised. Grouper, acting as a collection of cells made what sounded like a somewhat subversive remark. Did the cells that constituted Grouper equal a conspiracy? When Grouper reproduced, the cells produced would be clones of – thus identical to – some of Grouper’s cells. Did that make them a continuing conspiracy? No doubt the Justice Department lawyers would have a splendid time sorting through that mess.
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