Latest freezing frog science….

A quick check around the scientific literature to see what’s new since the 2008 review by Glenn Tattersall and Gordon Ultsch we relied on heavily last year to give advice.

You can view an abstract of the review but unless you’re in a science institute you won’t be able to download the whole thing – though an e-mail to Glenn should get you a pdf.

So it was interesting to see that one of this pair has published a more recent summary – very technical physiology stuff (bit beyond me, if I’m honest) – but should you be so inclined you can in fact read the whole article for free.

As should be the case you can get the gist from the abstract, saving yourself the solid 3-4 hrs reading needed to fully digest a 10 page close printed article like this.

In essence the story doesn’t seem to have changed too much since last year.

Frogs can survive pretty much indefinitely – or at least through the winter – by breathing under water but at a reduced metabolic rate. They do fine as long as there’s oxygen – even quite a low amount; when there’s no oxygen they die in about a week.

Turtles – which of course we don’t have here as native creatures – can do much the same thing, but some species can survive much longer without oxygen: 4-5 months. They rival Crucian Carp in this remarkable tolerance to lack of oxygen.

Here’s the abstract, which is just about comprehensible to the intelligent reader:

– Successful overwintering under ice by an air-breathing vertebrate requires either effective aquatic respiration if dissolved O2 is available or the capacity for prolonged anaerobic metabolism if O2 supplies are limiting.

– Frogs can remain aerobic for many weeks when submerged at low temperature, even at water PO2 as low as 30mmHg, but are unable to survive even 1 week in anoxic water.

– Fuel reserves of hibernating frogs limit aerobic submergence, whereas acidosis may limit anoxic submergence.

– Freshwater turtles can also satisfy all or most of their O2 needs in well aerated water at low temperature by aquatic respiration, but certain species, in particular painted and snapping turtles, can also survive for up to 4–5 months without O2.

– Key adaptations of the painted turtles, and presumably snapping turtles, include metabolic depression and the exploitation of the shell and other bones to buffer lactic acid. As in frogs, glycogen and glucose are the only fuel sources during anoxia, and stores do not seem to be limiting in the painted turtle.

– Significant differences in anoxia tolerance exist among chelonian species that can be attributed, at least in part, to the magnitude of metabolic depression, the effectiveness of lactic acid buffering, and the size of glycogen stores.


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