Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Avenue, Windsor, Ontario, N9B 3P4, Canada.
Rapid Commun Mass Spectrom. 2011 Apr 30;25(8):1008-16. doi: 10.1002/rcm.4946. Epub 2011 Mar 15.
Stable isotopes of neonatal vertebrates reflect those of their mother's diet and foraging location. Evaluating feeding strategies and habitat use of neonates is consequently complicated by the maternal isotopic signal and its subsequent elimination with growth. Thus, methods that measure the loss of the maternal signal, i.e. when the isotopic signal of a neonate reflects its own diet, are needed. Values of δ(13)C and δ(15)N were measured in liver and muscle tissues of <1 year old bull (Carcharhinus leucas) and Atlantic sharpnose (Rhizoprionodon terraenovae) sharks and related to age using, total length, date sampled and umbilical scar stage (USS). We observed a decline in δ(13)C and δ(15)N values with age that was different among species, similar among isotopes, and greater in liver than in muscle; highlighting that retention of the maternal signal is dependent on species-specific life history and tissue characteristics. USS was most effective for assessing the loss of the maternal isotopic signal in the faster growing Atlantic sharpnose shark, but was less effective for the slower growing bull shark. Total length and date sampled were overall less effective and may be more informative for slower growing species when coupled with USS, as variable size at birth and misclassification of animals >1 year old, which remain in nursery habitats, increase the variability of the isotopic values. Consideration of the maternal signal and measuring its loss are thus necessary when analyzing the stable isotopes of young animals, as there is potential to misinterpret feeding strategies, over-estimate trophic position and incorrectly assign carbon source.
新生脊椎动物的稳定同位素反映了其母亲的饮食和觅食地点。因此，评估新生儿的喂养策略和栖息地利用情况变得复杂，因为存在母体同位素信号及其随生长而消除的问题。因此，需要测量母体信号损失的方法，即当新生儿的同位素信号反映其自身饮食时的方法。我们测量了<1 岁的牛鲨（Carcharhinus leucas）和大西洋尖吻鲭鲨（Rhizoprionodon terraenovae）的肝脏和肌肉组织中的 δ(13)C 和 δ(15)N 值，并使用总长度、采样日期和脐痕阶段（USS）与年龄相关。我们观察到 δ(13)C 和 δ(15)N 值随年龄的下降在不同物种之间存在差异，在同位素之间相似，在肝脏中比在肌肉中更为明显；这表明母体信号的保留取决于物种特有的生活史和组织特征。USS 对于评估快速生长的大西洋尖吻鲭鲨中母体同位素信号的损失最为有效，但对于生长较慢的牛鲨则不太有效。总长度和采样日期总体上效果较差，当与 USS 结合使用时，对于生长较慢的物种可能更具信息性，因为出生时的大小变化和>1 岁的动物的分类错误，这些动物仍留在育苗栖息地，增加了同位素值的变异性。因此，在分析幼年动物的稳定同位素时，需要考虑母体信号并测量其损失，因为有可能错误解释喂养策略、高估营养位置和错误分配碳源。
