Changes in ion content and transport during development of embryonic rainbow trout |
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Authors: | K J Barrett D G McDonald M J O'Donnell |
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Institution: | Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4KI |
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Abstract: | Wet mass and water content of four lots of whole eggs did not change throughout embryonic development of rainbow trout Oncorhynchus mykiss. Eggs in all four lots accumulated Na+. Eggs in lots 2 and 4 also accumulated Ca2+ and Cl-, whereas eggs in lot 1 showed no significant change in Ca2+ or Cl- and eggs in lot 3 showed no change in Cl-and a small loss of Ca2+. Although the Na+ content of embryonic tissues increases in the later stages of development, the yolk sac content remained constant, indicating uptake of Na+ from the environment. Na+ uptake by whole eggs was non-saturable, consistent with diffusion of Na+ across the chorion into the perivitelline fluid. Na+ uptake in dechorionated embryos was saturable, as was Ca2+ uptake by both whole eggs and dechorionated embryos, consistent with active uptake or facilitated diffusion mechanisms at the surface of embryos. Very low Ca2+ uptake rates in dechorionated embryos suggest that the Ca2+ uptake mechanism is not fully developed until after hatching. |
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Keywords: | trout eggs embryos ionoregulation ion transport |
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