Grossmann Johannes, Starck J Matthias
Department of Biology, Biocenter Martinsried, University of Munich (LMU), Grosshadernerstrasse 2, D-82152 Planegg-Martinsried, Germany.
Zoology (Jena). 2006;109(4):310-7. doi: 10.1016/j.zool.2006.05.001. Epub 2006 Sep 7.
The African rhombic egg eater (Dasypeltis scabra) is a colubrid snake feeding exclusively on bird eggs. Frequency of feeding is governed by the seasonal availability of bird eggs; i.e., long fasting intervals change with relatively short periods when plenty of food is available. Intermittent feeding snakes show a remarkable postprandial increase of metabolic rate and digestive organ size. The postprandial increase in metabolic rate (specific dynamic action, SDA) in snakes is affected by meal size, temperature, and meal composition. A major portion of SDA in snakes is allocated to gastric function and the breakdown of the meal. We hypothesize that SDA in egg eaters is lower than in other snake species, because egg eaters feed on "liquid" food that does not require enzymatic breakdown in the stomach. We also hypothesized that other components of the postprandial response of egg eaters (e.g., size changes of the intestine and the liver) do not differ from other snakes. The standard metabolic rate and metabolic response to feeding were measured using closed-chamber respirometry. Size changes of small intestine and liver were measured using high-resolution transcutaneous ultrasonography. Standard metabolic rates of fasting egg eaters were in the same range of mass specific values as known from other snakes. Within 24h after feeding, oxygen consumption doubled and peaked at 2 days after feeding. At the same time, the size of the small intestine and the cross-sectional diameter of the liver increased. Within 2 days after feeding, the size of the mucosal epithelium doubled its thickness. Liver size increased significantly within 24h reaching maximum size 2-4 days after feeding. The size of both organs returned to fasting values within 7-10 days after feeding. The postprandial response of African rhombic egg eaters shows the same pattern and dynamics as known from other snake species. However, the factorial increase of metabolic rate during SDA is the lowest reported for any snake. A comparison with literature data supports the idea that SDA is mainly determined by gastric function and that it is low in egg eaters because they do not have to break down solid meals in the stomach as other snake species do.
非洲菱形食卵蛇（Dasypeltis scabra）是一种游蛇科的蛇类，仅以鸟蛋为食。进食频率受鸟蛋的季节性可得性支配；也就是说，长时间的禁食间隔会随着食物充足的相对短时期而变化。间歇性进食的蛇在餐后会出现代谢率和消化器官大小显著增加的情况。蛇餐后代谢率的增加（特殊动力作用，SDA）受餐量、温度和食物组成的影响。蛇的SDA的一大部分被分配到胃功能和食物的分解上。我们假设食卵蛇的SDA低于其他蛇类，因为食卵蛇以“液体”食物为食，这种食物在胃中不需要酶解。我们还假设食卵蛇餐后反应的其他组成部分（例如，肠道和肝脏的大小变化）与其他蛇类没有差异。使用封闭室呼吸测定法测量标准代谢率和对进食的代谢反应。使用高分辨率经皮超声测量小肠和肝脏的大小变化。禁食的食卵蛇的标准代谢率在与其他蛇类已知的质量比特定值相同的范围内。进食后24小时内，耗氧量翻倍，并在进食后2天达到峰值。与此同时，小肠的大小以及肝脏的横截面积增加。进食后2天内，黏膜上皮的厚度增加了一倍。肝脏大小在24小时内显著增加，在进食后2 - 4天达到最大尺寸。两个器官的大小在进食后7 - 10天内恢复到禁食时的值。非洲菱形食卵蛇的餐后反应显示出与其他蛇类相同的模式和动态。然而，SDA期间代谢率的阶乘增加是所有蛇类中报道最低的。与文献数据的比较支持了这样一种观点，即SDA主要由胃功能决定，并且食卵蛇的SDA较低是因为它们不像其他蛇类那样必须在胃中分解固体食物。
