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　　Amphibian Thermoregulation

　　In contrast to mammals and birds,amphibians are unable to produce thermal energy

through their metabolic activity,which would allow them to regulate their body

temperature independent of the surrounding or ambient r,the idea

that amphibians have no control whatsoever over their body temperature has been proven

false because their body temperature does not always correspond to the surrounding

amphibians are poor thermoregulators,they do exercise control over

their body temperature to a limited degree.

　　Physiological adaptations can assist amphibians in colonizing habitats where

extreme conditions tolerance range in body temperature represents the

range of temperatures within which a species can species of North American

newt is still active when temperatures drop to-2°C while one South American frog

feels comfortable even when temperatures rise to 41°C—the highest body temperature

measured in a free-ranging ly it has been shown that some North

American frog and toad species can survive up to five days with a body temperature

of-6°C with approximately one-third of their body fluids other tissues

are protected because they contain the frost-protective agents glycerin or glucose

Additionally,in many species the tolerance boundaries are flexible and can change

as a result of acclimatization(long-term exposure to particular conditions).

　　Frog species that remain exposed to the sun despite high

diurnal(daytime)temperatures exhibit some fascinating modifications in the skin

structure that function as morphological amphibian skin is fully

water permeable and is therefore not a barrier against evaporation or solar

African savanna frog Hyperolius viridiflavus stores guanine crystals

in its skin,which enable it to better reflect solar radiation,thus providing

protection against tree frog Phyllomedusa sauvagei responds to

evaporative losses with gland secretions that provide a greasy film over its entire

body that helps prevent desiccation(dehydration).

　　However,behavior is by far the most important factor in

principal elements in behavioral thermoregulation are basking(heliothermy),heat

exchange with substrates such as rock or earth(thigmothermy),and diurnal and annual

avoidance behaviors,which include moving to shelter during the day for cooling and

hibernating or estivating(reducing activity during cold or hot

weather,respectively)Heliothermy is especially common among frogs and toads:it

allows them to increase their body temperature by more than 10° Andean toad

Bufo spinulosus exposes itself immediately after sunrise on moist ground and attains

its preferred body temperature by this means,long before either ground or air is

correspondingly warmed.A positive side effect of this approach is that it accelerates

the digestion of the prey consumed overnight,thus also accelerating

thermy is a behavior present in most amphibians,although pressing

against the ground serves a dual purpose:heat absorption by conductivity and water

absorption through the effect of thigmothermy is especially evident in the

Andean toad during rainfall:its body temperature corresponds to the temperature of

the warm earth and not to the much cooler air temperature.

　　Avoidance behavior occurs whenever physiological and morphological adaptations

are insufficient to maintain body temperature within the vital nal

activity in amphibians with low tolerance for high ambient temperatures is a typical

thermoregulatory behavior of al avoidance behavior is extremely

important in many s whose habitat lies in the temperate latitudes

are confronted by lethal low temperatures in winter,while species dwelling in and

and semi-and regions are exposed to long dry,hot periods in summer.

　　In amphibians hibernation occurs in mud or deep holes away from of

the Pyrenees Mountains,the natterjack toad offers a good example of

hibernation,passing the winter dug deep into sandy sely,natterjacks in

southern Spain remain active during the mild winters common to the region and are

instead forced into inactivity during the dry,hot summer estivation

also occurs by burrowing into the ground or hiding in cool,deep rock crevasses to

avoid desiccation and lethal ambient ians are therefore hardly at

mercy of ambient temperature,since by means of the mechanisms described above they

can more than exercise some control over their body temperature.

　　paragraph 1

　　In contrast to mammals and birds,amphibians are unable to produce thermal energy

through their metabolic activity,which would allow them to regulate their body

temperature independent of the surrounding or ambient r,the idea

that amphibians have no control whatsoever over their body temperature has been proven

false because their body temperature does not always correspond to the surrounding

amphibians are poor thermoregulators,they do exercise control over

their body temperature to a limited degree.

　　ing to paragraph 1,what indicates that amphibians have some control over

their body temperature?

　　ians can regulate their metabolic rates to generate energy.

　　ians use the same means of thermoregulation as mammals and birds do.

　　 body temperature of amphibians sometimes differs from the temperature of