Turtles and heat issues

[Hawkeye]

Just a little query from those who know about turtles.

I was reviewing some underwater video I took of a large turtle in Forster sleeping under a rock. Just thinking afterwards how does a turtle maintain body temperature when it is immersed in water for large periods of time and can be immobile sleeping (ie no muscle activity). I know that reducing its metabolism allows it to stay underwater for ages but how then does it gain enough temperature to ge around?

Cheers Hawkeye

[hey_im_sam]

hmm i'm not sure about the getting up and going again hawkeye! and not really sure but maybe turtles are just less concerned by low body temperatures then other reptiles. with water being such a good conductor i spose they'd have to be.

anyway my main reason for replying was a slightly related sidenote - read on craig latta's turtle care sheet at http://www.vhs.com.au/pages/CareShee...erTurtles.html

i found this really interesting...

*****
CIRCULATORY SYSTEM

A turtle’s heart has only three chambers. Many things including increased activity, temperature and increased pressure during diving affect their heart rate. An increase in ambient temperature will cause an increase in heart rate, thus increasing a turtle’s metabolism. As a turtle dives, pulmonary resistance increases and the heart rate decreases. The scientific name for this is ‘Bradycardia’. When a turtle dives, the level of oxygen in the blood decreases as the body uses it. Anaerobic metabolism takes over causing an increase in carbon dioxide. Most aquatic turtles can tolerate extremely high levels of carbon dioxide in the blood. After about 15 minutes of being submerged and the oxygen supply depleted, the brain will divert as previously mentioned, to anaerobic metabolism. Here the brain can continue to function effectively for around 2- 3 hours depending on the species and size of the individual.
******

[snakehunter]

Im not sure about others, but eastern long necks have a preferred body temp (PBT) of around 25 degrees celcius, as mentioned already, water holds heat better than air so the water temp doesnt drop as quickly as the ambient temp

[africancichlidau]

If it gets too cold they hibernate, if it gets too hot or dry they aestivate. Their body temp rises and falls with that of the water.

[Hawkeye]

True but that has to be water temp at the turtles body temp and the temp in the sea can vary 10 degrees even in a very localised area (trust me on that one).

Its interesting that turtles can anaerobically metabolise with their brains. Humans certainly cannot. I wonder what the cost is metabolically (ie to they have lower pH in blood?)

Interesting....

Cheers Hawkeye

[africancichlidau]

Sorry Hawks, didn't realise you were talking Marine Turtles.

[hey_im_sam]

hawkeye - where it reads "Most aquatic turtles can tolerate extremely high levels of carbon dioxide in the blood." i assumed it meant they could handle a blood with a low pH... i mean no matter how good a buffer, large amounts of Co2 are always going to make blood more acidic - maybe something that's a poison to humans isnt to turtles.

Anyway i found that entire article great - you should check it out if you're interested

[Hawkeye]

Yeah thats what I meant but by definitions a proper buffer will keep pH within a very small zone and will not allow pH to change. I'll have a closer look at that article. I am interested now.

Cheers Hawkeye

[roadkill5000]

whats aestivate

[hey_im_sam]

aestivation is the same sort of thing as hibernation - except that it's what they do in hot/dry weather rather than cold.

[roadkill5000]

like when they bury themselves in mud when a dam drys up :

[hey_im_sam]

yep!
water holding frogs are big on aestivation too, they drink as much as they can, bury themselves, and then shed about 3 layers of skin - creating a watertight bubble around them. as soon as the water penetrates as deep as they are they dig their way out.