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First published online January 12, 2004
Journal of Experimental Biology 207, 597-606 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00792

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Maternal effects of egg size on emu Dromaius novaehollandiae egg composition and hatchling phenotype

Edward M. Dzialowski^1,* and Paul R. Sotherland²

¹ Department of Biological Sciences, University of North Texas, PO Box 305220, Denton, TX 76203, USA
² Department of Biology, Kalamazoo College, Kalamazoo, MI 49007, USA

View larger version (30K): [in a new window]   Fig. 1. Mass of emu egg components increase with fresh egg mass (Me). Filled circles, albumen mass (Ma=0.49Me–11.1; r2=0.87); open circles, albumen dry mass (Mad=0.06Me–5.1; r2=0.75); filled squares, yolk mass (My=0.48Me+13.4; r2=0.82); open squares, yolk dry mass (Myd=0.24Me–6.2; r2=0.76); triangles, shell mass (Ms=0.13Me+1.5; r2=0.68).

View larger version (23K): [in a new window]   Fig. 2. Mass of water and solids in yolk-free hatchlings and eggs increase with yolk-free hatchling mass (Myfh) and with fresh egg mass (Me). Filled inverted triangles, yolk-free hatchling water content (Myfhw=0.7Myfh+2.2; r2=0.95); filled diamonds, egg water content (Mew=0.57Me+13.4; r2=0.94). Open inverted triangles, yolk-free hatchling solids (Myfhs=0.25Myfh+1.0; r2=0.76); open diamonds, egg solids (Mes=0.3Me–11.6; r2=0.85).

View larger version (26K): [in a new window]   Fig. 3. Mass of emu hatchling components increase with fresh egg mass (Me). Filled circles, hatchling (yolk-free hatchling + residual yolk) mass (Mh=0.64Me+9.6; r2=0.82); filled triangles, yolk-free hatchling mass (Myfh=0.46Me+20.5; r2=0.64); open triangles, yolk-free hatchling dry mass (Myfhd=0.12Me+6.7; r2=0.43); filled squares, residual yolk mass (Mry=0.18Me–10.9; r2=0.24); open squares, residual yolk dry mass (Mryd=0.11Me–12.0; r2=0.28).

View larger version (20K): [in a new window]   Fig. 4. (A) Mass of dry yolk solids consumed (predicted initial egg yolk solids – measured residual yolk solids) by embryos during development increases with yolk-free hatchling mass (Myc=0.29Myfh–3.94; r2=0.52). (B) Mass of residual yolk solids rM decreased as mass of yolk-free hatchling increased irrespective of initial egg mass (rMryd=–1.03rMyfhd+0.41; r2=0.58). Statistical residuals from the regression of the mass of residual yolk solids and the mass of yolk-free hatchling on initial egg mass were obtained from regression equations in Figs 1 and 3 and plotted against each other, revealing a trade-off between retaining residual yolk and producing a hatchling.

View larger version (21K): [in a new window]   Fig. 5. Linear dimensions of hatchling emus increase with yolk-free hatchling mass (Myfh). Squares, right tibiotarsus length (Lt=0.09Myfh+44.4; r2=0.70); circles, culmen length (Lc=0.02Myfh+30.3; r2=0.17).

View larger version (20K): [in a new window]   Fig. 6. Blood volume, blood osmolality, hematocrit and hemoglobin content plotted as a function of yolk-free hatchling mass (Myfh). (A) Hatchling blood volume (Vb=0.09Myfh+0.43; r2=0.57), (B) hematocrit (Hct=0.02Myfh+29.2; r2=0.05), (C) hemoglobin (Hb=0.006Myfh+9.4; r2=0.03) and (D) blood osmolality (Osm=–0.03Myfh+325.2; r2=0.02).