What would mermaids, underwater weaponry and underwater farming look like if they evolved naturally?

ok let's put a pin in underwater communication for now let's assume mermaids have the same adaptation for salt as dolphins would it make sense for them to sweat salt water? Also are there any shallow hydro-thermic water areas currently on earth?

Pretty sure sea animals don't sweat.

Regarding shallow hydrothermals, it seems so: For one, hot-springs are such, and in Wikipedia's article on those it mentions "submarine thermal springs", and as a specifically example a spring in partially submerged caves on the coast of Italy.

However, I'm no expert in this, so I stand to be corrected by any who know better on the subject!

What are you looking for? Something big enough to support an ecosystem?

like yeah something big enough to support an ecosystem and near the shore

Then you have a problem: hot springs aren't big enough, nor do they emit sufficient total heat, to accomplish that. You would need hundreds of square miles of hot springs, and that's more like fault system (a "crack" between two continents). The reason that most such fault zones are deep underwater is because they are the result of two tectonic plates running into each other—one is forcing the other to go down underneath itself, and that plunges the fault zone into a very deep valley.

The other option is a fault zone that forces one plate over another, but that produces mountains and volcanoes. A shallow water fault zone probably isn't impossible, but it will require some fancy planetary dynamics to explain how it happened.

Does your story require an Earth like planet? I assume it's in perpetual darkness for some reason? Perhaps if you provided some details someone could think of a solution.

I wonder if an Io-like planet might have the requisite volcanic activity.

I think Wild wants life on his fictional planet, so it needs an atmosphere and water.

Io-like planets can have atmospheres and water. The reason why Io itself doesn't have an atmosphere is because its gravity is too weak to hold it against the Sun's X-rays, extreme UV radiation and solar wind and Jupiter's radiation belts. Volcanoes and internal heat themselves do not make much of a difference.

I guess I need you to explain what "Io like" means in this context.

Io-like heatflow with many large volcanoes. Tupan Patera has a cross-section of 79km, reduce the heatflow just a little and you can have hot springs over an area of over a thousand square kilometres.

So you mean a moon, larger than Io so that it can retain it's atmosphere, yet still small enough to experience volcanization due to the gravitational effects of orbiting a much larger planet with some other nearby moons?

Edited by DeMarquis on May 28th 2023 at 4:48:25 AM

my story takes place on earth not a whole new planet also I don't want hot springs I want it to be in the ocean and also I guess they could change on shore and develop water heating as early Homo sapiens sapiens forced them deeper underwater also I use she/her pronouns btw

yeah but this is a Human Subspecies so it seems likely they'd keep the ability to sweat

Edited by Wild-Starfish on May 28th 2023 at 7:41:03 AM

Io-type volcanism can occur on planets of any size. In fact, since tidal heating increases with the radius of the planet, a more massive body has more volcanism than a small one given identical orbital parameters.

Mind you, moons have maximum size limits - no more than 0.001-0.0001 of the planet's mass, and their "lifespan" decreases with mass.

Good to know.

@Wild-Starfish: Well, I guess I just don't see how to pull that off on Earth, sorry.

As for sweating, if they broke off from our evolutionary tree long enough ago to evolve tails and suchlike, then they could have lost sweating. There's certainly no reason to evolve sweating salt water, at least not while in the water.

Sweating could be adapted as a means of expelling excess salt.

While immersed in saltwater? Methinks that evolution could come up with a better solution. What is excess for a salt-water animal anyway? How much excess salt do fish generate, and how do they get rid of it?

Penguins do a similar thing using the supraorbital glands. I'm not sure if they do that while submerged or not.

they didn't though they are Apparently Human Merfolk that are more like Selkies then traditional mermaids in fact they broke off so recently that they are a Human Subspecies

Edited by Wild-Starfish on Jun 24th 2023 at 4:17:37 AM

But then would enough time have passed for them to have the same adaptations to salt-water as have dolphins? (As you mentioned above?)

My thought is perhaps more in the opposite direction: perhaps they do still sweat, as a result of their human ancestry—but it's (I imagine) a problem for them, something that they work around. (And perhaps a trait that is reduced in them, on its way to being adapted out.)

Wait, wait...

If they are like selkies, does that mean they shapeshift too?

Or is the change just superficial and they can get on land by changing they shape?

Like an octopus?

Or maybe they are instead like the seal folk from Galápagos?

EDIT: nvm, glossed over the "merfolk" bit

Edited by MorningStar1337 on Jun 24th 2023 at 6:21:38 AM

I mean are we talking supernatural domestication (like telepathy and mind control) stuff or 'natural' domestication?

Referring to how real life domestication works I'm pretty sure the local Merfolk race could breed Lemon Sharks (or other sharks that are intelligent) over time into companions and/or hunting 'dogs'

In terms of "domesticating" a shark, the closest you can get in the ocean, is if you manage to "strike a deal" with the shark to behave in a certain way in an equal exchange.

Respect the shark's rules and it will respect you in return.

Break that deal and all bets are off with the shark.

It would be a delicate tightrope to say the least.

I don't think Sharks can be domesticated as we think of it. Sharks just don't communicate or conceptualize enough to even understand the idea of being given commands. You'd need some kind of genetically modified shark with improved intelligence and some means of communicating.