Katrina G. Salvante


Ph.D. Student (finished M.Sc. at CWE in December 2000).

Title of M.Sc. Thesis:

Variation and Regulation of Plasma Levels of the Egg Yolk Precursors: Vitellogenin and Very-Low Density Lipoprotein


Tony Williams

Summary of current research:

I investigated the physiological basis of individual variation in female reproductive traits (egg size, clutch size, and timing of laying) in Zebra Finches (Taeniopygia guttata), focusing on a) the role of the yolk precursors, vitellogenin (VTG) and very-low density lipoprotein (VLDL), and b) hormonal control of egg size. Plasma VTG exhibited marked inter-individual variation (up to 10-fold) and discernible daily variation, but also high intra-individual repeatability.Mean egg mass was positively correlated with plasma VTG levels in females on a low-quality seed diet, but these traits were negatively correlated in females on a high quality egg-food supplemented diet. Mean egg mass was larger on the egg-food diet suggesting that small egg size is limited by the pool of plasma yolk precursors, while the production of large eggs might deplete the plasma pool (perhaps due to high uptake rates). The heritability of the yolk precursors did not differ from zero (n = 28 families). In contrast, mean egg mass, body mass, and tarsus length were highly heritable (h2 = 0.488 to 0.783), similar to estimates from free-living species. Yolk precursor levels were positively genetically correlated with each other and with laying interval and tarsus length, but were negatively correlated with mean egg mass and clutch size. Corticosterone (B) treatment a) decreased breeding propensity by almost 50%, b) delayed breeding by an average of one week for B-treated females that did breed, and c) was associated with significantly lower plasma VTG levels during the time when control females were initiating laying. However, once they did breed, B-treated females did not differ from control females in egg size, clutch size, or precursor levels at the 1st-egg stage (even though they still had elevated B levels).

 Previous research: 

B.Sc. in Zoology and B.A. in Psychology from University of Washington, Seattle.

I was a research assistant on a project with Dr. Marilyn Ramenofsky and Dr. John Wingfield from UW and Dr. Sara Hiebert from Swarthmore College, examining the role of corticosterone in the regulation of torpor in captive Rufous Hummingbirds (Selasphorus rufus).We modified an existing radioimmunoassay for corticosterone to measure the hormone concentration of hummingbird cloacal fluid.

 Acknowledgements / Collaborators: 

Research funded by an NSERC operating grant to Tony Williams.

 Recent Publications: 

Hiebert, S.M., Salvante, K., Ramenofsky, M., and Wingfield, J.(in press)Corticosterone and nocturnal torpor in the rufous hummingbird.General and Comparative Endocrinology.

Hiebert, S.M., Ramenofsky, M., Salvante, K., Wingfield, J., and Gass, C.L.(in press)Noninvasive methods for measuring and manipulating corticosterone in hummingbirds.General and Comparative Endocrinology.

 Recent Conference Presentations:

Salvante, K.G., and Williams, T.D.2001.Hormonal control of reproduction: Effects of corticosterone on timing of laying, egg size, clutch size, and yolk precursor levels.Abstract submitted for an oral presentation at the annual meeting of the Society for Integrative and Comparative Biology, Chicago, IL.

Salvante, K.G., Challenger, W.O., and Williams, T.D.2000.Daily variation in vitellogenin in two species of passerine birds: Implications for identifying environmental estrogens. Oral presentation at the Western Regional Conference on Comparative Endocrinology, Corvalis, OR.

Salvante, K.G., Challenger, W.O., and Williams, T.D.2000.Diurnal and daily variation in vitellogenin levels during the laying cycle.Oral presentation at the annual meeting of the Society for Integrative and Comparative Biology.Abstract published in American Zoologist. 39(5): 21A-22A.

Vezina, F., Salvante, K.G., and Williams, T.D.2001.The metabolic cost of yolk precursor production.Abstract submitted for an oral presentation at the annual meeting of the Society for Integrative and Comparative Biology, Chicago, IL.

Williams, T.D., Christian, J.K., Salvante, K.G., and Challenger, W.O.2000.Investigating physiological variation and trade-offs using phenotypic engineering.Oral presentation at the Experimental Biology 2000 Conference.Abstract published in Comparative Biochemistry and Physiology.126B(Suppl 1): S105.

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