Читать книгу Blackwell's Five-Minute Veterinary Consult: Reptile and Amphibian - Javier G. Nevarez - Страница 19

Reptiles have one‐fifth to one‐seventh of a mammal’s metabolism at 37 degrees C (98.6 degrees F) and one‐tenth of the food requirements compared with birds and mammals. The digestive efficiency of herbivores is 30–85% and that of carnivores is 70–95%. Reptiles are capable of switching to anaerobic metabolism to satisfy physiological needs during diving, fast sprints, etc., but this causes a significant drain of energy reserves.

Reptiles are ectothermic, but some species are capable of generating or retaining large amounts of heat. Some pythons can generate heat by muscle contractions to maintain the temperature of their eggs. Leatherback turtles (Dermochelys coriacea) have large amounts of body fat, which allows them to retain heat. Thermoregulation is primarily controlled by the preoptic nucleus of the hypothalamus but the pineal gland and parietal eye may also play a role. Most reptiles regulate their temperature by heliothermy or thigmothermy. Heliotherms absorb heat from radiant sources such as the sun. Thigmotherms absorb heat via conduction by being in contact with hot surfaces. Because of a greater ability to regulate heart rate, reptiles can heat up faster that they cool down. Right to left blood shunts allow reptiles to bypass the lungs and decrease evaporative losses. Vasodilation and constriction of peripheral vessels also aid in thermoregulation. During the day, the extremities will warm up first and peripheral vasodilation occurs. At night, peripheral vasoconstriction combined with a slower heart rate allows retention of core body heat. The heating and cooling of larger reptiles occurs more slowly. In general terms, the majority of common reptile species cared for in captivity typically have a preferred optimal temperature zone of 20–38 degrees C (68–100.4 degrees F) for most species. However, due to the wide array of natural habitats from which reptiles originate, the preferred optimal temperature zone can be quite varied.