Nitrogen stable isotopes ratios (δ15 N) were determined for selected tissues (muscle, liver, blood and yolk) of pregnant females and their embryos of a placental viviparous species, the Pacific sharpnose shark (Rhizoprionodon longurio) and a yolk-sac viviparous species, the speckled guitarfish (Pseudobatos glaucostigmus). The R. longurio embryo tissues were 15 N-enriched compared to the same tissues in the pregnant female, using the difference in δ15 N (Δδ15 N) between embryo - adult. Mean Δδ15 N was 2.17 ‰ in muscle, 4.39 ‰ in liver and 0.80 ‰ in blood. For P. glaucostigmus, embryo liver tissue was significantly 15 N-enriched in comparison with liver of the pregnant female (Δδ15 N mean = 1.22 ‰); whereas embryo muscle was 15 N-depleted relative to the muscle of the pregnant female (Δδ15 N mean = -1.22 ‰). Both species presented a significant positive linear relationship between Δδ15 N and embryo total length (Lt ). The results indicated that embryos have different Δδ15 N depending on their reproductive strategy, tissue type analysed, and the embryo Lt .

中文翻译：

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怀孕女性及其胚胎的同位素 ( δ 15 N ) 关系：比较胎盘和卵黄囊胎生弹鳃

测定了妊娠雌性及其胎盘胎生物种、太平洋锐鼻鲨（Rhizoprionodon longurio）和卵黄囊胎生物种的选定组织（肌肉、肝脏、血液和卵黄）的氮稳定同位素比率（δ15 N），有斑点的吉他鱼（Pseudobatos glaucostigmus）。与怀孕雌性的相同组织相比，R. longurio 胚胎组织富含 15 N，使用胚胎 - 成体之间 δ15 N (Δδ15 N) 的差异。平均 Δδ15 N 在肌肉中为 2.17 ‰，在肝脏中为 4.39 ‰，在血液中为 0.80 ‰。P. glaucostigmus 胚胎肝组织与妊娠女性肝脏相比，显着富含 15 N（Δδ15 N 平均值 = 1.22 ‰）；而胚胎肌肉相对于怀孕女性的肌肉缺乏 15 N（Δδ15 N 平均值 = -1.22 ‰）。两个物种在 Δδ15 N 和胚胎总长度 (Lt ) 之间呈现显着的正线性关系。结果表明，胚胎具有不同的 Δδ15 N，这取决于它们的繁殖策略、分析的组织类型和胚胎 Lt。