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First published online May 1, 2006
Journal of Experimental Biology 209, 1874-1882 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02200
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Removal of the chorion before hatching results in increased movement and accelerated growth in rainbow trout (Oncorhynchus mykiss) embryos

Marcie M. Ninness, E. Don Stevens and Patricia A. Wright*

Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada


Figure 1
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  		Fig. 1. Number of movements per hour in chorionated (chorion intact) and dechorionated (chorion removed) rainbow trout embryos over a period of 25 h. Negative numbers indicate times before hatch, time 0 indicates the 5-h interval in which hatching occurred (defined as when the embryo body was free of the chorion), and positive numbers indicate times post-hatch. Values are means ± s.e.m. (N=4). *Significantly different from chorionated values (P<0.05).

 

Figure 2
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  		Fig. 2. Oxygen consumption (µmol min–1 g–1 embryonic body dry mass) in chorionated (chorion intact) and dechorionated (chorion removed) rainbow trout embryos 3 days before hatch to 3 days after hatch. Embryonic body dry mass is the dry mass of the embryo only, separated from the yolk. Negative numbers indicate days before hatch and, time 0 indicates when hatching started (hatching did not necessarily occur in the respirometer) and positive numbers indicate days post-hatch. Values are means ± s.e.m. (N=9).

 

Figure 3
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  		Fig. 3. Correlation between the number of movements (per hour) and oxygen consumption (µmol min–1 g–1 embryonic body dry mass) in chorionated (open circles, chorion intact), dechorionated (closed circles, chorion removed), and hatched (triangles) rainbow trout embryos around the time of hatch (3 days before hatch to 3 days after hatch). Embryos were dechorionated 3 days before hatching. Movements were measured while the embryos were in the respirometers.

 

Figure 4
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  		Fig. 4. Embryonic body dry mass (mg) in chorionated (chorion intact) and dechorionated (chorion removed) rainbow trout embryos 6 days before hatch to 3 days after hatch. Embryos were dechorionated 6 days before hatching (–6 days). Embryonic body dry mass is the dry mass of the embryo only, separated from the yolk. Negative numbers indicate days before hatch, time 0 indicates when hatching started and positive numbers indicate days post-hatch. Values are means ± s.e.m. (N=8, with each value consisting of a pooled dry mass of 5 embryos). *Significantly different from chorionated values (P<0.05).

 

Figure 5
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  		Fig. 5. Distribution of protein content (mg protein ind–1) in whole embryos (embryonic body plus yolk sac; A), and in the embryonic body and yolk fractions (B) of chorionated (chorion intact) and dechorionated (egg case removed) rainbow trout 3 days before hatch to 3 days after hatch. (C) The values for the embryonic body shown in B but on a different scale, in order to highlight the differences in protein content (mg protein ind–1) between chorionated and dechorionated embryos. Embryos were dechorionated 3 days before hatching (–3 days). Negative numbers indicate days before hatch, time 0 indicates when hatching started and positive numbers indicate days post-hatch. Values are expressed as means ± s.e.m. (N=8). *Significant difference from chorionated value (P<0.05).

 




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