Prenatal and postnatal transfer of fatty acids from mother to pup in the hooded seal |
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Authors: | S J Iverson O T Oftedal W D Bowen D J Boness J Sampugna |
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Institution: | (1) Canadian Institute of Fisheries Technology, Technical University of Nova Scotia, B3J 2X4 Halifax, Nova Scotia, Canada;(2) Department of Zoological Rescarch, National Zoological Park, Smithsonian Institution, 20008 Washington, D.C., USA;(3) Marine Fish Division, Bedford Institute of Oceanography, B24 4A2 Dartmouth, Nova Scotia, Canada;(4) Department of Chemistry and Biochemistry, University of Maryland, 20742 College Park, MD, USA;(5) Present address: Department of Biology, Dalhousie University, B3H 4J1 Halifax, Nova Scotia, Canada |
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Abstract: | Unlike most mammals, hooded seal (Cystophora cristata) pups are born with a substantial layer of adipose tissue. Subsequently, during the brief lactation period of only 4 days,
fasting mothers mobilize enormous amounts of lipid from blubber and secrete milk (60% fat) at rates of 10 kg·day-1. Pups gain 7 kg·day-1 due primarily to the deposition of fat in blubber. We measured blubber content and fatty acid composition of blubber and
milk in hooded seal mother-pup pairs at birth and over the 4-day lactation period to examine the nature and source of fetal
lipids, the incorporation of maternal blubber fatty acids into milk lipid, and patterns of fatty acid deposition in suckling
young. The fatty acid composition of the blubber of the newborn was notably different from that of its mother. Fetal deposition
was likely due to a combination of both fetal synthesis and direct placental transfer of maternal circulating fatty acids.
The blubber of the newborn was characterized by high levels (>90% of total fatty acids) of saturated and monounsaturated fatty
acids of primarily endogenous origin. In particular, the fetus appeared to have high Δ-9 desaturase activity as evidenced
by the large amounts of 14:1n-5 (4.2%) and 16:1n-7 (37.0%) in newborn blubber compared to maternal blubber (0.2% and 14.1%,
respectively). Nevertheless, essential and long-chain polyunsaturated fatty acids of the n-3 and n-6 families, which could
only have originated by direct transfer from the mother, comprised>7% of pup blubber fatty acids and indicated greater rates
of placental transfer than found in humans. In hooded seal mothers, rapid lipid transfer during the brief lactation period
appeared to be facilitated by direct incorporation of mobilized fatty acids into milk. Although some differences in proportions
of specific fatty acids were found between milk and maternal blubber, most of these differences declined over the course of
lactation. However, selective mobilization of 20:5n-3 from maternal blubber into milk was apparent throughout lactation and
resulted in elevated levels in pup blubber at weaning compared to maternal blubber. Ingested fatty acids were deposited directly
and without modification into the blubber of pups, and by 4 days the fatty acid composition of pup blubber was virtually identical
to that of the milk consumed. |
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Keywords: | Placental transfer Lactation Fatty acids Adipose tissue Hooded seal Cystophora |
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