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Heating youself in cold conditions is quite easy. You can produce internal heat and keep it in(warm-blooded) or get it from sun, find hot springs... or even eat something warmer than you. However, it is not so easy with too much heat...

For my alien world, I imagined a species of crustacean, not too different compared with crabs, with one few little changes. First of all, their inside is always around 35 degrees Centigrade, a little colder than normal human. This makes them warm-blooded - quite an evolutionary jump! A jump is even more pronounced, because they live in hot springs near the volcanoes, in nearly-boiling water. I guess anything can live in such place, just not too long, but this little guy actually survives by cooling himself.

I don't want them to leave water. I imagined themselves to be equipped with biological heat pump, which allows my fire crabs to keep cool in scalding hot water. I just have some problems with making it realistic enough. The animal is not intelligent, so cooling is not artificial, it is part of biology of it.I thought that maybe they are using heat for synthesis of some complicated chemicals, which is then ejected outside, but I'm not sure if it is even possible.

I have no problem with outside of crustacean being hot, but inside must stay cold(ish). No magic, pure science. I guess this question is too unrealistic for hard-science, but science-based is a must.

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    $\begingroup$ If this is to be science-based, then what was the evolutionary pressure for favoring being warm-blooded when they live in near-boiling water? $\endgroup$ – Frostfyre Mar 10 '17 at 18:16
  • $\begingroup$ I used warm-blooded in meaning they they can self-regulate their internal temperature, without being dependant on external sources. Sorry, I used nearest translation for term in my mother tongue, which is more or less "constant-temperature". $\endgroup$ – Feanorek Mar 10 '17 at 18:33
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    $\begingroup$ @Feanorek You are good in your translation: 'warm-blooded' or endothermy means ability to maintain a constant temperature. However, he is saying that in our world, warm-blooded creatures have the advantage of being more active in cold temperatures. This crab would not run into that problem. $\endgroup$ – kingledion Mar 10 '17 at 18:39
  • $\begingroup$ @Frostfyre - At a handwavy kinda guess, I'd think that since they had an abundance of heat, it wasn't worth getting rid of all of it instead of tolerating as much as they could (therefore setting a higher equilibrium temperature), and then later developing the ability to keep warm as part of general thermal regulation and a precaution against over-cooling - sort of (or perhaps exactly opposite) the way we have mechanisms for cooling down even though we usually spend more energy warming ourselves up in a cooler environment. $\endgroup$ – Megha Mar 12 '17 at 5:01
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Access to novel food sources is a very strong evolutionary pressure and results in “progressive” adaptations.

Rather than having a continuous heat pump that requires one end to be hot, as kingledion objects to in his answer, why not allow for cycling over time?

The animal moves in exceptionally close to the volcanic vents, or even down into the outflow caves, to grab food that other preditors can’t reach. Besides increased tolerance to dart in and grab, they then evolve temporary active cooling.

An endothermic chemical reaction is used to chill the shell and exoskelliton, and the animal can range well into the hot zone as long as the stored up supply lasts.

Then, it retreats to more tolerable waters, in keeping with its own biochemistry, where it recharges the supply of chemicals. This reaction releases heat, but it is now in the cool zone and can do so as slowly as necessary to prevent overheating, and even use more normal regulation devices like pumping water over a heat sink (adapted from a copy of its gill structure) to handle it.

That is, the total immersion in the hot environment can be separated in time from the cooler pumped-to environment, and the rates of heat exchange can be different on each end.

Now, if you wanted a Cephalopod instead of a Crustacean, you could have a squid shape with long feeding tenticles that reach into the hot spring, with the main body some distance away and the tail farthest of all. Active cooling of the “hands” follows.

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  • $\begingroup$ yeti crabs seem to do something similar to what you are describing. $\endgroup$ – user25818 Mar 11 '17 at 0:00
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    $\begingroup$ I like this answer more than previous, it looks more realistic. I will wait for a day, and then accept if nothing better comes by :) $\endgroup$ – Feanorek Mar 11 '17 at 12:35
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An AC unit operates using adiabatic expansion

A vapor compression refrigeration unit works in four stages. A liquid-vapor mix of refrigeration fluid flows through the cooling coils, absorbing heat from the inside of your refrigerator or house, and ideally coming out as a saturated vapor. Then a compression pump adiabatially increases pressure and temperature until the working fluid is a superheated vapor (note: superheated doesn't mean 'superhot', it just means that it is above boiling point of the working fluid). Next the hot vapor travel through the heat sink, shedding excess thermal energy and cooling down to a saturated liquid. Finally, the saturated liquid passes through an adiabatic expansion nozzle, that causes the fluid to vaporize, and in the process cool off.

Thermodynamically not possible with this cycle

This process (like all non-ideal processes) produces waste heat. For your AC or refrigerator, the waste heat from the electric coils of the pump mechanism will be hotter than the heat sink (outside of house for AC, inside of house for refrigerator), and will thus be disposed of outside of the refrigerants ability to remove heat. However, for that to work with this crab, the waste heat must be at a higher temperature than the surrounding (near-boiling liquid). So basically, some part of your crab, specifically the part that is pumping refrigerant around under his shell, must be hotter than the hot springs. The refrigeration cannot remove more heat than is generated as waste heat in this process.

If that is the case, why not just let the entire crab be that hot? If part of your crab can take the heat, presumably all of it can too. Besides, it is not like there aren't crabs that live in hot water already, and some other invertebrates can thrive at 80C and survive up to 150 C.

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  • $\begingroup$ Actually whole idea is having animal with heat pump. So, if I understand right, it can work as long as compression pump and heat-sink is outside an animal and is hotter than surroundings? $\endgroup$ – Feanorek Mar 10 '17 at 18:49
  • $\begingroup$ @Feanorek A heat pump is exactly the same as a vapor-compression refrigerator, except that the cooling coils are in the heat sink (outside) and the heating coils are on the inside of your house. So the same principles would apply. $\endgroup$ – kingledion Mar 10 '17 at 18:58
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    $\begingroup$ Note that many physical processes can be used, not just gas compression. I saw someone build a refrigerator based on stretching rubber bands. Endothermic chemical reaction was used in an episode of Rough Science. $\endgroup$ – JDługosz Mar 10 '17 at 20:28
  • $\begingroup$ Making endothermic reactions continuously is a neat idea. Probably pretty expensive though maybe the hotsprings have the minerals for a good process. $\endgroup$ – user25818 Mar 10 '17 at 21:05
  • $\begingroup$ «If part of your crab can take the heat, presumably all of it can too.» Why? Some organs might need cooler temperatures. All critical biochemestry that cannot adapt to hotter environment would move to a single cooled zone. Mammal testicals are a simple example. $\endgroup$ – JDługosz Mar 10 '17 at 22:02

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