Foreword: I'm aware of the limitations of the square-cube law involved in sizing an animal up, as these limitations have been relentlessly stressed in every discussion of realistic fantasy creatures. In this case, I'm discussing not an animal, but a slime mold with animal-like motility.
Slimes in fantasy video games are all rather similar to each other in appearance and behavior. They are macroscopic and generally sphere or droplet-shaped, and capable of moving under their own power, often elastically bouncing meters into the air. They absorb solid matter directly through their gelatinous surface, and it's often implied, stated or demonstrated that this is how they eat. Though they are extremophiles found in every biome (e.g. forest, tundra, island, volcanic mountain, swamp), they are fairly weak creatures, and they can be dispatched with the first sword you get.
I want to construct a more realistic slime. I've looked for the largest slime molds that exist in the real world and have identified Brefeldia maxima as a potential candidate for improvement. It's a single cell approximately a meter across, and it can weigh 20 kilograms. It's not spherical, though - it's a layer about a centimeter thick. Nevertheless, its size is interesting.
The traits I am looking for are:
- Spherical, ovoid, or droplet shape. This conserves surface area relative to volume, as far as I understand it.
- Able to move at a speed humans can observe. Bouncing is not required. It doesn't even need to be fast compared to a human, just visibly moving. But when I say "moving," I mean that the entire slime physically changes position, not that it grows towards food like a slime mold in a dish.
I do not need these slimes to have big cartoony eyes like they have in some games.
Naturally, some questions follow this:
- What is the largest such a slime mold could be under the limits of the square cube law? Could it be a single cell? I assume this would be governed by the efficiency of transporting food chemicals within its mass and the strength of the protein fibers it's made from.
- Would such a slime mold at such a size actually be as weak as video games imply, a one-hit kill? Or would it have to have a thick, stiff "crust" so it could support itself, and such a crust would be hard for a typical sword to cleave?
- By what means does it eat? Does it need to be rooted in place for some time? Or does it sense food around it somehow and absorb the food through its surface? And if it has a crust, how would this be reconciled?
- Could it possibly inhabit the wide range of biomes that fantasy games show? Or would its range be limited?
- Is a macroscopically motile slime possible? How would it achieve this movement? Is there a way for a slime mold to produce motor impulse? I tentatively suspect rolling could be viable, but I don't know too much about slime molds. Maybe it would crawl like a slug?
Thanks in advance for your answers.