School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, KZN, South Africa.
Comp Biochem Physiol A Mol Integr Physiol. 2013 Jun;165(2):97-105. doi: 10.1016/j.cbpa.2013.02.023. Epub 2013 Feb 27.
African egg-eating snakes (Dasypeltis) feed only on freshly laid bird eggs which they perforate within their esophagus before swallowing the liquid contents and regurgitating the empty shell. Compared to a snake's typical intact meal, the liquid diet of Dasypeltis would expectedly generate a more moderate postprandial metabolic response and specific dynamic action (SDA). Free-ranging Dasypeltis feed over a range of ambient temperatures and thereby experience predicted temperature-dependent shifts in the duration and magnitude of their postprandial metabolic response. Such shifts would undoubtedly be shared among different species and age classes of Dasypeltis. To examine these expectations, we measured pre- and postprandial metabolic rates of adult Dasypeltis inornata and adult and neonate Dasypeltis scabra in response to liquid egg meals weighing 20% of snake body mass at 20, 25, 27, 30, and 32 °C. With an increase in body temperature, postprandial metabolic profiles of neonate and adult snakes became narrower and shorter in duration. Specific dynamic action varied among temperature treatments, increasing from 20 to 32 °C. Standard metabolic rate, postprandial peak metabolic rate, and SDA scaled with mass exponents that typically did not differ from 1.0. As expected, Dasypeltis digesting a liquid egg diet experienced a more modest postprandial response and SDA, expending on average only 10.6% of the meal's energy on the breakdown, absorption, and assimilation of the egg meal, whereas other colubrids consuming intact rodent or fish meals expend on average 16.3% of the meal's energy on digestion and assimilation. Actively foraging and feeding throughout the avian egg laying season enable Dasypeltis to survive when eggs are not available. The adaptive suite of traits that enable Dasypeltis to consume eggs of large relative size and ingest only the liquid contents may also be joined by physiological adaptations specific to their liquid diet and extended bouts of fasting.
非洲食蛋蛇（Dasypeltis）只吃刚产下的鸟蛋，它们会在食道中刺穿蛋壳，然后吞下蛋液，再吐出空蛋壳。与蛇通常完整的食物相比，Dasypeltis 的液体饮食预计会产生更温和的餐后代谢反应和特殊动力作用（SDA）。自由放养的 Dasypeltis 在一系列环境温度下进食，因此会经历其餐后代谢反应的持续时间和幅度随温度变化的预测性转变。这种转变无疑会在不同的 Dasypeltis 物种和年龄组之间共享。为了检验这些预期，我们测量了成年 Dasypeltis inornata 和成年和幼体 Dasypeltis scabra 在 20、25、27、30 和 32°C 下对 20%体重的液体蛋餐的餐前和餐后代谢率。随着体温升高，幼蛇和成年蛇的餐后代谢谱变得更窄，持续时间更短。特殊动力作用在不同温度处理之间有所不同，从 20°C 到 32°C 逐渐增加。标准代谢率、餐后峰值代谢率和 SDA 与质量指数呈比例关系，通常与 1.0 没有差异。正如预期的那样，消化液体蛋饮食的 Dasypeltis 经历了更为温和的餐后反应和 SDA，平均仅将 10.6%的饮食能量用于分解、吸收和同化蛋餐，而其他以完整啮齿动物或鱼类为食的游蛇平均将 16.3%的饮食能量用于消化和同化。Dasypeltis 在整个鸟类产卵季节积极觅食和进食，使其能够在没有鸡蛋时存活。使 Dasypeltis 能够消耗相对较大的鸡蛋并仅摄入蛋液的一系列适应性特征，可能还伴随着特定于其液体饮食和长时间禁食的生理适应。
