Читать книгу Blackwell's Five-Minute Veterinary Consult: Reptile and Amphibian - Javier G. Nevarez - Страница 48

When housed in captivity, providing an appropriate temperature and thermal gradient is critical for amphibian health. Amphibians may show a variety of clinical signs at extreme temperatures (Figure 2– see web image supplementary content for section I).

Amphibians are sensitive to desiccation and have developed techniques for regulating body temperature and retaining moisture. Changes in posture, locomotion, and skin color can be used to regulate temperature. Cooling can be accomplished by standing away from the ground and changing to a pale body color to decrease heat absorption. Peripheral vasodilation or constriction can also regulate the rate at which they dissipate or absorb heat. Some amphibians, anurans in particular, can produce glandular secretions that allow them cover part of their bodies in a waxy substance to protect against desiccation. These secretions are usually limited to the dorsal skin only, as ventral skin must remain thin to allow water uptake via the pelvic drink patch. Up to 80% of the total water uptake may occur through this pelvic patch. Dried mucus may also be used to cover the skin. Finally, they have iridophores that provide high skin reflectivity near the infrared spectrum (700–900 μm) to decrease solar heat exposure.

Some amphibians have developed specialized methods for surviving cold temperatures through a technique known as super cooling. Super cooling lowers the freezing point of tissues through a combination of physiological adaptations: Higher amount of fibrinogen, glucose‐transporting proteins and ice‐nucleating proteins in blood, low molecular weight carbohydrates (glycerol or glucose) in blood and tissues, and increasing plasma osmolarity by dehydration. These adaptations also promote ice growth in extracellular compartments while sparing the cells. In addition, they have good anoxia tolerance for freeze‐induced ischemia.