TY - JOUR AU - Cherel Yves, Hobson Keith A. PY - 2015// TI - Milk isotopic values demonstrate that nursing fur seal pups are a full trophic level higher than their mothers T2 - Rapid Commun. Mass Spectrom. JO - Rapid Communications in Mass Spectrometry SP - 1485 EP - 1490 VL - 29 IS - 16 KW - Animals KW - Suckling KW - Suckling: physiology KW - Carbon Isotopes KW - Carbon Isotopes: analysis KW - Female KW - Fur Seals KW - Fur Seals: physiology KW - Lactation KW - Male KW - Milk KW - Milk: chemistry KW - Nitrogen Isotopes KW - Nitrogen Isotopes: analysis KW - Nutritional Status KW - N2 - RATIONALE: In mammals including humans, mother-to-offspring transfer of nutrients has been the focus of several isotopic studies. Measurement of δ(13) C and δ(15) N values were mainly conducted on easily sampled tissues such as blood and hair that allow the calculation of apparent discrimination factors (∆(13) C and ∆(15) N) between offspring and maternal tissues. Quantifying real ∆(13) C and ∆(15) N values requires the measurement of the δ(13) C and δ(15) N values of milk, the exclusive food of newborns. Surprisingly, little isotopic information is available on milk and its biochemical components (lipids and proteins).METHODS: Paired blood and milk samples from 10 lactating females and their pups were collected from two otariid species, the Antarctic and subantarctic fur seals. Tissue δ(13) C and δ(15) N values were measured using continuous-flow isotope ratio mass spectrometry (CFIRMS) on maternal and offspring blood, and on whole milk, lipid-free milk and milk lipids, thus allowing the calculation and comparison of apparent (maternal blood to offspring blood) and real (lipid-free milk to offspring blood) ∆(13) C and ∆(15) N values.RESULTS: In both fur seal species, the apparent ∆(13) C values averaged ~0.0 ‰. Lipid-free milk was slightly (13) C-depleted compared with both maternal and pup blood and it was strongly (13) C-enriched (~6.3 ‰) compared with milk lipids. In contrast, the apparent and real ∆(15) N values averaged 1.2-1.4 and 2.6-3.0 ‰, respectively, the differences being explained by the ~1.5 ‰ lower milk δ(15) N values than those of maternal blood.CONCLUSIONS: In fur seals, the low apparent ∆(15) N translated into a higher real ∆(15) N value, amounting to a full trophic level, which is in agreement with the almost never verified hypothesis that (15) N differences between mothers and their offsprings should reflect one complete trophic level. The study highlights the need to measure milk isotopic values to disentangle the nutritional mother-to-offspring relationships. SN - 0951-4198 UR - http://dx.doi.org/10.1002/rcm.7243 N1 - exported from refbase (http://publi.ipev.fr/polar_references/show.php?record=6170), last updated on Mon, 01 Jul 2024 18:30:10 +0200 ID - CherelYves2015 ER -