Biodiversity Research Institute (IrBio) and Department of Animal Biology, Faculty of Biology, University of Barcelona, Barcelona, Spain.
Rapid Commun Mass Spectrom. 2012 Jul 30;26(14):1596-602. doi: 10.1002/rcm.6267.
In stable isotope research, the use of accurate, species-specific diet-tissue discrimination factors (i.e., Δ(13)C and Δ(15)N) is central to the estimation of trophic position relative to primary consumers and to the identification of the dietary sources of an individual. Previous research suggested that the diet of fin whales from the waters off northwestern Spain is overwhelmingly based on krill, thus permitting reliable calculation of discrimination values in this wild population.
After confirming that the stable isotope ratios (δ(13)C and δ(15)N values) in muscle from 65 aged fin whales remained constant through age classes (4-65 years), the signatures were determined in muscle, bone protein, skin, liver, kidney, baleen plates and brain, as well as food (krill), from a subset of individuals to calculate discrimination factors. Signatures were determined by means of elemental analysis isotope ratio mass spectrometry (EA-IRMS) using a ThermoFinnigan Flash 1112.
The isotopic values remained constant regardless of age. The mean Δ(15)N values between krill and whale tissues ranged from 2.04 in bone protein to 4.27‰ in brain, and those of Δ(13)C ranged from 1.28 in skin to 3.11‰ in bone protein. This variation was consistent with that found in other groups of mammals, and is attributed to variation in tissue composition and physiology.
Because discrimination factors are relatively constant between taxonomically close species, the results here obtained may be reliably extrapolated to other cetaceans to improve dietary reconstructions. The skin discrimination factors are of particular relevance to monitoring diet through biopsies or other non-destructive sampling methods. The large difference in bone protein discrimination factors from those of other tissues should be taken into consideration when bone collagen is used to determine trophic level or to assess diet in paleodietary isotopic reconstructions.
在稳定同位素研究中，使用准确的、物种特异性的饮食-组织分辨因子（即 Δ(13)C 和 Δ(15)N）对于相对于初级消费者的营养位置的估计以及个体的饮食来源的识别是至关重要的。先前的研究表明，来自西班牙西北部水域的长须鲸的饮食主要基于磷虾，因此可以在这个野生种群中可靠地计算分辨值。
在确认 65 头老龄长须鲸的肌肉中的稳定同位素比值（δ(13)C 和 δ(15)N 值）在年龄组（4-65 岁）之间保持不变后，从一组个体中确定肌肉、骨蛋白、皮肤、肝脏、肾脏、鲸须板和大脑中的特征，并计算分辨因子。通过使用 ThermoFinnigan Flash 1112 的元素分析同位素比质谱法（EA-IRMS）确定特征。
同位素值无论年龄大小都保持不变。磷虾和鲸鱼组织之间的平均 Δ(15)N 值范围从骨蛋白中的 2.04 到大脑中的 4.27‰，而 Δ(13)C 值范围从皮肤中的 1.28 到骨蛋白中的 3.11‰。这种变化与其他哺乳动物群体中的变化一致，归因于组织成分和生理学的变化。
由于分辨因子在分类上相近的物种之间相对稳定，因此此处获得的结果可以可靠地外推到其他鲸目动物，以改善饮食重建。皮肤分辨因子对于通过活检或其他非破坏性采样方法监测饮食特别重要。当使用骨胶原蛋白确定营养水平或评估古饮食同位素重建中的饮食时，应考虑到骨蛋白分辨因子与其他组织的分辨因子之间的巨大差异。
