Miller Ashadee K, Erasmus Barend F N, Alexander Graham J
School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.
School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Comp Biochem Physiol A Mol Integr Physiol. 2014 Sep;175:110-4. doi: 10.1016/j.cbpa.2014.06.002. Epub 2014 Jun 15.
Constraints on physiological processes imposed on ectotherms by environmental temperatures can be severe, affecting many aspects of their biology. Included in the suite of physiological processes affected is gut motility, with below optimum temperatures generally resulting in slow gut passage. Trachylepis margaritifer (rainbow skink) however presents an unusual pattern whereby gut passage time decreases at a low temperature compared to when at an intermediate temperature. It has been suggested that this may be a 'cutting-your-losses' response whereby nutritional gain is sacrificed by voiding the digesta to reduce the risk of these rotting within the gut at these low temperatures, and if this is so, it should result in reduced digestive performance at 25°C. We tested this hypothesis by measuring appetite, apparent digestive efficiency (ADE) and apparent assimilation efficiency (AAE) in T. margaritifer. We found that although temperature significantly affected appetite and gut passage time, it did not affect digestive efficiency. Both ADE (>90%) and AAE (>80%) were high and temperature-independent across the range tested. Thus, the 'cutting-your-losses' hypothesis does not explain faster gut passage at 25°C. High digestive parameters could be maintained by increasing concentrations of digestive enzyme at low temperatures but remains to be tested in this species.
环境温度对外温动物生理过程施加的限制可能很严重，会影响它们生物学的许多方面。受影响的生理过程包括肠道蠕动，温度低于最佳温度通常会导致肠道通过缓慢。然而，珍珠彩虹蜥（Trachylepis margaritifer）呈现出一种不寻常的模式，即与处于中等温度时相比，在低温下肠道通过时间会减少。有人认为这可能是一种“减少损失”的反应，即通过排空消化物来牺牲营养获取，以降低在这些低温下消化物在肠道内腐烂的风险，如果是这样，那么在25°C时消化性能应该会降低。我们通过测量珍珠彩虹蜥的食欲、表观消化效率（ADE）和表观同化效率（AAE）来检验这一假设。我们发现，虽然温度显著影响食欲和肠道通过时间，但它并不影响消化效率。在所测试的温度范围内，ADE（>90%）和AAE（>80%）都很高且与温度无关。因此，“减少损失”假设并不能解释在25°C时更快的肠道通过情况。可以通过在低温下增加消化酶浓度来维持高消化参数，但这仍有待在该物种中进行测试。
