Filling Up on Fats

Abstract

PHYSIOLOGY Although weighing only 30 g, semipalmated sandpipers are impressive endurance athletes—each summer these migrant shorebirds migrate from their breeding grounds in the Arctic to their winter home in South America, with one leg being a nonstop, 3-day transoceanic journey of 4500 km. Before embarking on this flight, they spend 2 weeks on the mudflats of the Bay of Fundy, Canada, where they feed voraciously on a burrowing shrimp ( Corophium ). Intriguingly, Corophium is unusually rich in n -3 polyunsaturated fatty acids (PUFA), which form a class of phospholipids that increases the fluidity of cell membranes and may facilitate fatty acid mobilization. Because burning fats is the means by which migrant birds typically fuel long flights, Maillet and Weber hypothesized that the sandpipers use the dietary PUFA acquired during their stopover as an endurance-enhancing substance to prepare their flight muscles for migration. To investigate this, they examined the composition and distribution of fatty acids in the birds at various stages of fat loading. In less than 2 weeks, dietary n -3 PUFA was both incorporated into flight muscle cell membranes and stored within fat depots; in the latter tissues, much of the PUFA had been converted to monounsaturated fatty acids, as a more readily oxidized, energy-dense form of fuel. — PAK J. Exp. Biol. 209 , 2686 (2006).