During extreme environmental conditions such as summer sleep (aestivation) and winter sleep (hibernation), frogs respire exclusively through their:

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Frogs undergo aestivation (summer sleep) and hibernation (winter sleep) to protect themselves from extreme heat and cold by burrowing deep into the mud. During these dormant periods, pulmonary and buccal respiration cannot occur. The frogs rely entirely on cutaneous respiration, where gaseous exchange takes place exclusively through their moist skin. Lungs and buccal cavity are used on land, while gills are present only in the larval (tadpole) stage. Answer: skin