CSIRO Oceans & Atmosphere, Indian Ocean Marine Research Centre, Crawley, WA, 6009, Australia.
CSIRO Oceans & Atmosphere, Biosciences Precinct, St Lucia, Queensland, 4067, Australia.
Rapid Commun Mass Spectrom. 2020 Aug 30;34(16):e8839. doi: 10.1002/rcm.8839.
Ecologists often need to make choices about what body parts (tissues or organs) of an animal to sample. The decision is typically guided by the need to treat animals as humanely as possible, as well as the information that different body parts can provide. When using stable isotopes, decisions are also influenced by whether specimens would require preservation, and whether they have properties (such as high lipid concentrations) that would influence measurements. Sometimes we cannot use a preferred tissue (for example, because of ethical or logistical constraints), and in such cases an ability to reliably predict stable isotope composition for one tissue from data yielded by another would be useful.
In this study we analysed multiple tissues (skin, whole blood, red blood cells, plasma and nail) from green turtles (Chelonia mydas) to evaluate variation in C:N ratios, and test hypotheses about the intercept and slope of regressions of stable carbon and nitrogen isotope compositions among tissues.
Regression models revealed that linear relationships were present for most comparisons, except those involving the δ C of skin, and the slopes (β ) of most regressions were different from unity. The C:N ratios of skin were significantly higher and more variable than those of other tissues. The δ C and δ N of nail were highly correlated with those of the whole blood, red blood cells and plasma. Nail and red blood cells showed low variation in C:N.
The patterns in slopes of regressions indicate that comparisons of measurements yielded by different tissues of wild animals are complicated by the fact that the tissues are unlikely to be in isotopic equilibrium with their diet. Of the tissues used in this study, nail is simple to collect, requires minimal disturbance to the animal and no special preservation; these traits should make it attractive to turtle ecologists, but more information is needed on aspects such as growth rates.
生态学家通常需要选择动物的哪些身体部位（组织或器官）进行采样。这一决定通常受到尽可能人道地对待动物的需要以及不同身体部位可以提供的信息的指导。在使用稳定同位素时，决策还受到标本是否需要保存以及它们是否具有影响测量的特性（例如高脂质浓度）的影响。有时我们无法使用首选组织（例如，由于道德或后勤限制），在这种情况下，能够从另一种组织的数据中可靠地预测一种组织的稳定同位素组成将是有用的。
在这项研究中，我们分析了绿海龟（Chelonia mydas）的多种组织（皮肤、全血、红细胞、血浆和指甲），以评估 C:N 比的变化，并测试了稳定碳和氮同位素组成在组织之间回归的截距和斜率的假设。
回归模型表明，除了皮肤的δ C 之外，大多数比较都存在线性关系，而且大多数回归的斜率（β）都不同于 1。皮肤的 C:N 比明显高于其他组织，且变异性更大。指甲的δ C 和δ N 与全血、红细胞和血浆的高度相关。指甲和红细胞的 C:N 变化较小。
回归斜率的模式表明，比较不同组织的野生动物的测量值受到组织与饮食之间不太可能处于同位素平衡的事实的复杂化。在本研究中使用的组织中，指甲易于采集，对动物的干扰最小，无需特殊保存；这些特性应该对海龟生态学家有吸引力，但需要更多有关生长速度等方面的信息。
