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Index of Subjects Don't know about tadpoles, but there's an 'old' scientific literature on temperature tolerance of adult frogs, usually focussing on lethal temperature. While many measurements that physiologists make need modern instrumentation to pursue properly, it has long been possible to control temperature and to measure it to 1/100 °C accuracy if needed, so temperature is a variable that has been explored quite a lot in the older biological literature. Two results I remember are that 'summer frogs' and 'winter frogs' are different, with summer frogs having a higher high-temperature tolerance before expiring, by perhaps 4°C (same species, from memory probably European Rana temporaria). The other result was that there's a trade-off between lethal temperature and exposure time. As you might expect, frogs lasted shorter and shorter times (criterion: still just able to recover from the heat shock), as the temperature was raised more and more, with an ultimate limit around 41-45°C. These are temperatures where proteins start to coagulate and become denatured, unless an animal can bring the temperature down by thermoregulating, or lose heat the other way by moving to a cooler area. One of the papers published in the 1940s by French scientists in Paris contains a footnote complaining bitterly that the work on temperature/frogs had been made extremely difficult because the laboratory had been requisitioned and taken over by the occupying German army (Wehrmacht) for a barracks -- their tests therefore had to be completed at home. They didn't say if there was any compensating gastronomic payoff. Perhaps you could stick a thermometer in your pool and record the temperature in mid-afternoon to see if it really hits 40°C or so -- it appears that we are in for more hot weather in August. Is there anywhere in the pond that is cooler, to which the tadpoles might retreat? Or might it be possible to provide artificial shade in one corner? Steve, Halifax ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Quoting Eleanor Lindsay <kelindsay@eastlink.ca>: > I have a small pond (approx 10'x5' and 3' deep) that is filled with > tadpoles each summer - spring peepers and occasional green/wood > frogs. In August and September the pond gets full sun from approx > 11.30am to 4.30pm and the water can get quite warm. Most tadpoles > have matured and are gone before this happens, but this year they > ?seem to have taken longer than usual and we had a few very hot days > in mid July, when there appeared to be still a lot of legless > tadpoles around, after which there was a major drop in sightings. Is > much known about heat tolerance limits in tadpoles? I have tried to > Google this, but am finding it hard to access any really helpful > articles. > > Eleanor Lindsay, > Seabright, St Margarets Bay
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