Plasma Yolk Precursor Dynamics during Egg Production by Female Greater Scaup (Aythya marila): Characterization and Indices of Reproductive State

We characterized dynamics of the plasma yolk precursors vitellogenin (VTG), very-low-density lipoprotein ( total VLDLTG), and VLDL particle size distribution during egg production by female greater scaup (order: Anseriformes, Aythya marila). We also evaluated VTG and total VLDL-TG as physiological indices of reproductive state. Mean (+/- 1 SE) plasma concentrations of VTG and total VLDL-TG for females with nondeveloped ovaries were 0.58 +/- 0.05 mu g Zn mL(-1) and 3.75 +/- 0.29 mmol TG L-1, respectively. Yolk precursor concentrations increased rapidly to maximum levels in association with small increases in ovary mass during rapid follicle growth. Mean concentrations of VTG and total VLDL- TG for females with a full ovarian follicle hierarchy were 3.38 +/- 0.40 mu g Zn m(-1) and mmol TG L-1, respectively. Concentrations of VTG 7.31 +/- 2.56 and total VLDL remained elevated throughout the laying cycle and decreased markedly by 3 d into incubation. Individual reproductive state (non-egg producing vs. egg producing) was more accurately identified by plasma profiles of VTG (90%) than by those of total VLDL-TG (74%). Greater scaup VLDL particle sizes during egg production were within the range for predicted yolk-targeted VLDL size (25-44 nm). We conclude that plasma profiles of VTG and total VLDL-TG can be used as nonlethal, physiological indices of reproductive state in greater scaup and should be of great utility to a variety of evolutionary, ecological, and applied conservation studies of reproduction in waterfowl.