How possible are my living cobblestone roads?

Question

In my story the cobblestone roads have each individual stone actually be alive, and during the day time they remain completely still. The stones (during the nighttime) almost kinda swim in between each other (below the stones lies a mucus, cement-like paste they make during their life), with the closest stone taking its place it left behind. Cobblestones tend to have two little simple eyes which can really only sense light. The cobblestones simply clone themselves to make more, and they eat by simply absorbing nutrients through their skin. When they are cracked, they either die or become hyper aggressive and even move during the daytime. I was thinking of what animals the stones would be related to, maybe siphonophores, overall this living-stone idea could definitely be improved upon with others ideas and knowledge with biology.

Answer 1

Thought provoking. Questions that you might want to answer: what is the protective strategy that the animal uses to adapt to the environment that the cobblestones are providing? How is it related to food gathering, a procreation cycle or evading predators?

There are a lot of ways that an animal could build a surface as protection.

model a: Protective sleeve- The cobblestones are manipulated by the animal . Giant silk spinning caddisflies? Apparently there is a form of fly called a caddisfly (Trichoptera)that builds a protective case for itself out of stones in the larvae phase. There is an artist that uses these flies by giving them precious materials to craft jewelry. Obviously they are small, have limited lifespans, and further would require assistance to consistently move in the direction of a road, such as paving it first with dead leaves, Algae, and detritus which they eat.

model b: burrower with a shell- In this example the cobblestones don't make the protective sleeve, the shells of the animal look like the cobblestones and they are using it as a form of camouflage like a kind of sand crab or turtle.

model c: The cobblestones are more like little nests. Multiple creatures are putting together a bunch of little homes that over time accrete to have a durable surface. Animal architects like this include many species.

Since this is fiction you would adapt one of these strategies to your invented animal. Then you get into another intriguing side of this question, which is how do humans engineer the road properly, in terms of toughness, durability, shape and causing the animal to live there.

Answer 2

Start with ticks.

The ocean has offered us many beautiful, tempting templates to begin with: barnacles, chitons, corals and so on. The problem is that these typically build their skeletons from simple minerals - calcium carbonate or silica, usually. These are sea creatures for good reason: because the minerals can be found in the sea, but don't come down in rain. Your cobblestones can't wander the countryside, and they need to be viable on roads crossing many different types of geography, so they need to be able to produce a strong skeleton without needing extra elements.

For this reason I would suggest starting with a tick. It isn't easy to crush a tick with your fingers (also probably inadvisable). They are evolved to survive a long time without food or water. What we need to do now is:

• Break their blood habit. Ticks have a mechanism to absorb water even from the air - we'll make them eat water. To survive, we'll give them photosynthetic organelles or symbiotes in their integument, and supplement this with a published method of photosynthesis said to be used by hornets. Note that this means the adult stage no longer needs to be able to expand its abdomen, so we can do internal reinforcement.
• Engineer the tick to withstand more crushing pressure. Typically, an unfed tick is much harder to crush than one that is engorged. But here, our engorged tick will develop many reinforcing partitions internally, which make it act like a large number of tough small ticks.
• Harden the integument. Everyone wants graphene for everything nowadays, but it seems hard to get, and I worry it may be overused in writing. Practically speaking, a road paved in teeth ought to last for a while, so maybe just transfer vertebrate enamelogenesis to the ticks to put miniature protecting teeth in their exoskeletons at the places with the most internal reinforcement.
• Scale up. Ticks are small, and there's a limit how far we're going to believe they grow. But they die, and leave these enhanced durable skeletons that are slowly ground to powder. So we'll suppose the existing ticks, foraging for trace nutrients, ever so slowly cement together the powdered or partially intact skeletons of the dead ticks and fill them in with a solid secretion. They work together to turn these round and round, creating large balls (cobblestones). The ticks have custom-made burrows reserved in these balls they create, so that each ball has multiple little tick legs and heads that can project out from it in every direction. They can work together to roll it around to a good spot if there is room to work with. The young, homeless ticks wander slowly in the spaces in this network, looking for their place.