Torroidal cells?

[tdvance]

Ok--Cells on Earth-based life are deformed spheres (genus 0, i.e. no "holes" like a donut). That seems reasonable, as I figure it is easier for a spherical cell to form randomly than anything more complex. A spherical cell might have evolved when, for some reason, self-replicating molecules got other molecules attached to them to protect them.

Still, it's certainly imaginable that by some random chance, a toroidal cell developed--nuclear material in a ring shape, with an inner-tube-like membrane surrounding it. It is not necessary that the DNA or equivalent actually be a ring--it could still be a thread with ends unconnected. The only thing is, would such a cell have any kind of survival advantage in some alien environment? If so, there would be a lot more and they would evolve.

There is more than one way you could split a donut--they might reproduce by becoming first, a two-holed figure-eight shaped donut, then breaking apart into two donuts, or perhaps it is simpler if a ridge forms on the equator and on the inner equator and the two ridges then squeeze together, so the final result looks like a donut sitting on top of a donut, both horizontal, and then they split into two.

Now, at some point, by mutation and/or accident, some donut will split in such a way that the two resulting donuts are linked. If this were to provide a survival advantage, it would be the start of a multi-cellular life form. Two different donut species getting linked somehow (I'm not sure how, but I'm sure it could happen) could become symbiosis.

Fast forward several billion years....multicellular macroscopic life forms with toroidal cells linked up like chains, mesh armor, or the like. If there is a survival advantage for toroidal cells, the aliens might have trouble imagining an alien species could possibly survive with spheroidal cells--with no way for cells to link together, they would just fall apart into dust, wouldn't they?

Now, if I could figure out how a cell could have a Mobius strip membrane so it mixes its outside with its inside....not so likely I guess.

Todd

[Nowhere Man]

There was a series of stories in Analog some years back (unfortunately I can't remember the author or any of the titles) that involved a biology based on toroidal cells. I thought it unlikely. Even more unlikely was that the torus motif was carried out into larger structures, including tire-shaped creatures and loopy plants.

Eventually the some of the cells were discovered to be able to form a shared consciousness and became kind of "live-in" guests in humans.

Surface tension is going to make cell-sized structures tend toward spheres. Toroids would need to be stronger than the surface tension, and probably need more energy to maintain.

Fred

[agingjb]

I am myself, as it happens, topologically, a torus. My cells are not, although I am told that they contain toroidal structures called plasmids.

[Noclevername]

Toroidal cells would be more complex, and require more enrgy and material to build. At some point, it is extremely likely that some line of toroid cells somewhere would take the shortcut of simply closing up the hole, thus eliminating all that extra membrane that needs to be grown, and extra surface area, and shortening internal pathways of energy and nutrient transfer. These un-holed cells would be more efficient than toroids, making them able to outcompete them. After a while, toroids might be extinct or relegated to a few relic species in isolated mud pools.