Milk isotopic values demonstrate that nursing fur seal pups are a full trophic level higher than their mothers.
Rapid Commun Mass Spectrom
; 29(16): 1485-90, 2015 Aug 30.
Article
em En
| MEDLINE
| ID: mdl-26212163
ABSTRACT
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.
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Isótopos de Carbono
/
Leite
/
Otárias
/
Animais Lactentes
/
Isótopos de Nitrogênio
Idioma:
En
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
França