Isotopic turnover rates and diet-tissue discrimination depend on feeding habits of freshwater snails

Estimates of animal diets and trophic structure using stable isotope analysis are strongly affected by diet-tissue discrimination and tissue turnover rates, yet these factors are often unknown for consumers because they must be measured using controlled-feeding studies. Furthermore, these parameters may be influenced by diet quality, growth, and other factors. We measured the effect of dietary protein content on diet-tissue discrimination and tissue turnover in three freshwater snail species. We fed lettuce to individually housed snails (n = 450 per species) for ten weeks, then half were switched to a high-protein diet. Isotopic values of muscle and gonad tissue were assessed at 48 and 80 days post-diet change. Snail discrimination factors varied by diet (low-protein > high-protein) and usually differed among species for both N and C, although species had similar carbon discrimination when fed the low-protein diet. Carbon turnover rates were similar among species for a given tissue t...

利用稳定同位素分析（stable isotope analysis）估算动物食性与营养结构的结果，会显著受到食性-组织分馏系数（diet-tissue discrimination）与组织周转率（tissue turnover rates）的影响；然而针对受试螺类而言，这类参数通常难以直接获取，必须通过受控饲喂实验完成测定。此外，日粮营养质量、生长状态及其他多种因素，均可能对这类参数造成影响。本研究以三种淡水螺类为研究对象，测定了日粮蛋白质含量对食性-组织分馏系数与组织周转率的影响。研究人员将单头饲养的螺类（每个物种设置450个生物学重复）以生菜饲喂十周，随后将其中一半个体更换为高蛋白日粮。在日粮更换后的第48天与第80天，分别测定其肌肉与性腺组织的同位素比值。螺类的食性-组织分馏系数随日粮类型存在显著差异（低蛋白日粮组＞高蛋白日粮组）；且氮（N）与碳（C）的分馏系数通常在不同物种间存在差异，不过当饲喂低蛋白日粮时，各物种的碳分馏系数较为相近。对于特定组织而言，不同物种间的碳周转率较为相近……