cold and warm-blooded

[ttyo888]

I was looking thru the wikipedia and then I discovered that the naked mole rat is cold blooded.

 

so lets discuss cold-blood and warm blood.

 

Basically the question is that can I assume that a cold blooded mammal will need less food than a warm-blooded one assuming that they are the same size. and can the cold blooded mammal reach evolutionarily a larger size than a warm blood?

 

And also how about a heterothermic one[in between cold and warm]

[Mokele]

Wikipedia is wrong - a quick romp through the scientific literature showed they have a low metabolic rate, 2/3 that of a mouse of the same size, but they can maintain their body temperature over a modest range of ambient temps. I've fixed the entry.

 

You are definitely right about food, though - warm blooded animals require a LOT more food than cold-blooded animals of the same size, usually between 10-20 times more.

 

As for size, that's more difficult. Cold blooded animals can be *smaller*, simply because warm-blooded species have a minimum size below which there's too much surface area per unit volume and they cool too quickly. But as far as upper limits, that's hard to say.

 

Part of the problem is thermal inertia - bigger animals of any sort take longer to cool due to less surface area per unit volume. As a result, very large mammals like elephants have lower metabolic rates per unit mass than mice, because they lose less heat. Once you reach dinosaur or whale size, even a low metabolism is enough to keep the body warm. Looking at the fossil record, there are giant ectotherms and giant endotherms, but both are rare enough that it's hard to say which is more likely.

[ttyo888]

But how do Amphibians managed to stay active and croak at night when it's cooler.

 

And also if lets say a mammal which has a body temperature like say 10 degrees lower and if it is to stay active and not enter hypothermia what adaptations does it need? a bit more fur or fat to insulate? or it's just not possible.

[Mokele]

But how do Amphibians managed to stay active and croak at night when it's cooler.

 

Different animals have different optimal muscle temperatures. The evolutionary change between high and low optimal temperatures seems to have occurs multiple times within diurnal and nocturnal geckos, for instance.

 

And also if lets say a mammal which has a body temperature like say 10 degrees lower and if it is to stay active and not enter hypothermia what adaptations does it need? a bit more fur or fat to insulate? or it's just not possible.

 

Well, if it's natural temperature is just 10 degrees lower than humans, then it's likely the animal will be just fine - remember, not all warm blooded animals have the same active temperature. Humans are 98.6 F, dogs and mice are 101F, elephants are 97 degrees, and birds can be 104 to 108 F. A Platypus has only a 90F temperature.

 

In each case, the animal's muscles, nerves and proteins have evolved to function optimally at those temperatures.

[cetus]

the fact of cold blooded or warm blooded dependeds on the type of animal mamal fish reptile ect

eg all mamals are warm blooded

all reptiles are cold blooded

[Mokele]

To some extent, but remember that what's alive today is a pale shadow of the true diversity of life. In the past, many animals were probably 'intermediates', and some may even be today. The leatherback sea turtle maintains its body a few degrees over the water temperature, for instance.

[ttyo888]

Is it possible to have an animal with a body temperature of only like within the range of 80 to 90F? Like having a thermostat turn on at a low setting?

[Mokele]

Definitely. AFAIK, no such species currently exists, but likely did at some point in the past during the transition from cold to warm blood.

[ttyo888]

How about Gigantotherms? they have a cold blooded metabolism and can get large.

 

But too bad there are no mammal Gigantotherms though. A gigantotherm with fur is a bit impossible right?

[Mokele]

Gigantothermy is always a possibility, but you have to be careful about overheating. Part of the reason elephants lack fur and have large ears is because of their need to dump excess heat.

[ttyo888]

hmm but elephants have a high body temperature like us... but if a mammal of elephant size has a body temperature like say a platypus?

 

sorry if I sound ridiculous.

[iNow]

hmm but elephants have a high body temperature like us...

They also live in extremely hot climates, and their large ears allow them to dissipate more heat due to their large surface area... Not to mention the flapping/fanning they can perform with them, an effect magnified when the elephant has wet itself or covered itself in mud.

 

 

but if a mammal of elephant size has a body temperature like say a platypus?

But what? Average body temp of elephant is 34-36 degrees C. Average body temp of a platypus is about 32-33 degrees C. Average body temp in humans is about 37 degrees C.

 

AFAIK... none of this has anything to do with cold versus warm bloodedness.

[ttyo888]

oh nevermind...

 

But lets say a nearly cold blooded animal with a lower body temperature like say 10 degrees above surrounding regardless mammal or reptile has thick layer fur or fat then will it be able to function? or will it suffer overheating or overcooling? And can a mammal absorb heat from surroundings?

[Mokele]

But lets say a nearly cold blooded animal with a lower body temperature like say 10 degrees above surrounding regardless mammal or reptile has thick layer fur or fat then will it be able to function? or will it suffer overheating or overcooling?

 

Ectotherms (and presumably near-ectotherms) can function in a wide range of temperatures.

 

And can a mammal absorb heat from surroundings?

 

Definitely, though most don't need to.

[ttyo888]

Ectotherms (and presumably near-ectotherms) can function in a wide range of temperates

 

 

Really? so if lets say a reptile with the proper adaptations like fur and fat and a thermostat can live at cooler areas without needing to eat a lot right? Something like a leatherback turtle which I find amazing.

 

But if a mammal needs to absorb a bit of heat which I can find no examples, it has to have a spot on the back that has black fur, right?

 

I am trying to see how an animal can relied on its low heated blood and also heat absorbing and conservation adaptations can live?

 

Or we just can't have something in between cold and warm blood?

 

Anyone?

[CaptainPanic]

Really? so if lets say a reptile with the proper adaptations like fur and fat and a thermostat can live at cooler areas without needing to eat a lot right? Something like a leatherback turtle which I find amazing.

 

But if a mammal needs to absorb a bit of heat which I can find no examples, it has to have a spot on the back that has black fur, right?

 

I am trying to see how an animal can relied on its low heated blood and also heat absorbing and conservation adaptations can live?

 

Or we just can't have something in between cold and warm blood?

 

Anyone?

Mammals have a constant body temperature in the core of their bodies. Your hands and feet can be far below the 37 deg C. In fact, your own hands will function at 10 degrees.

Therefore, it's very normal that mammals like to catch some sunshine in the early morning, after a cold night... or in case of more domestic animals, that your house cat wants to sit next to the heating after it went outside in the winter.

Animals also stay together to keep each other warm.

 

Another interesting case of a semi-warmblooded animal is the bumblebee. It's small, it has fur, and it's active in early spring and early morning. According to wikipedia, it can raise its temperature to 30 deg C.

[ttyo888]

hmm if say the creature has a core temperature of 29 to 32?

 

So to say are there creatures that are in between cold and warm blood. They are able to regulate their temperatures but also rely a bit on outside temperatures too.

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Ok... thanks

 

But hey I remember that we evolved from sail backe reptile right? So is it possible that a modern mammal due to reevolve a sail? Just asking.

[Mokele]

But hey I remember that we evolved from sail backe reptile right? So is it possible that a modern mammal due to reevolve a sail? Just asking.

 

Not actually - the sailback synapsids such as Dimetrodon and Edaphosaurus were 'cousins' to the lineage that led to modern mammals. Sails have turned up a few other times, such as in the dinosaurs Spinosaurus and Ournasaurus, as well as the extinct amphibian Platyhystrix. They seem to be for temperature regulation, but it's not very clear. It's possible it could re-appear, but until we actually know the function, it's hard to say under what conditions.

[ttyo888]

the closed thing to a sail or sail like structure are the ears of certain animals.

 

[Mokele]

Exactly - with such ears, why bother with a dorsal sail?

[ttyo888]

it might be possible that the creature's ears could have disadvantages?

[Mokele]

Oh, of course - energy expended to maintain them and build them during growth, providing an obstruction and possible handle for predators, etc. But those would apply to a sail, too.

 

There's also the question of why have either - why not just add a fan to the tail? Yet we don't see that as often, and never really for thermoregulation (usually for display or camouflage). Why not?

[ttyo888]

How about a dewlap?

 

But mammals cannot extend or fold back.

[Mokele]

Dewlaps in lizards are pretty much used exclusively for display.

[Mythranil]

This may be of interest regarding the conversation - some of the new findings in palaeontological research suggests that while the ornithischian dinosaurs were cold-blooded, that saurischian dinosaurs probably evolved to have warm blood. This was evidenced by bone fracture healing patterns. If I understood it right, bone heals in a different pattern depending on the bacteria living in the blood, and some bacteria require higher or lower temperatures to exist in the bloodstream. Several fractures in T. rex bones have shown healing patterns that indicate they must have been warm-blooded.

 

It makes sense, IMO. The more we find out about some of the later saurischians, the more it seems like they have warm-blooded tendencies. In the news a lot lately are fossilized feathers on such creatures.