Egg-size evolution in aquatic environments: does oxygen availability constrain size?

Selection against large eggs has been proposed for aquatic environments, putatively because large eggs should have more difficulty obtaining the required oxygen. Here, we use brown trout (Salmo trutta) eggs to provide an experimental test of this hypothesis. At high levels of dissolved oxygen (14 mg...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2002-11, Vol.269 (1507), p.2325-2330
Main Authors: Einum, Sigurd, Hendry, Andrew P., Fleming, Ian A.
Format: Article
Language:English
Subjects:
Animal nesting
Animals
Biological Evolution
Body Constitution - physiology
Ecological competition
Egg masses
Eggs
Evolution
Fecundity
Female
Female animals
Fertilization
Fresh Water
Freshwater
Incubation
Male
Maternal Effects
Metabolic Rate
Offspring Size
Ovum - drug effects
Ovum - physiology
Oxygen
Oxygen - pharmacology
Oxygen Consumption
Salmo salar
Salmo salar - growth & development
Salmo salar - physiology
Salmo trutta
Salmon
Salmonidae - growth & development
Salmonidae - physiology
Selection
Trout
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Summary:Selection against large eggs has been proposed for aquatic environments, putatively because large eggs should have more difficulty obtaining the required oxygen. Here, we use brown trout (Salmo trutta) eggs to provide an experimental test of this hypothesis. At high levels of dissolved oxygen (14 mg l−1), egg survival was high and independent of egg size. At low oxygen levels (2.3 mg l−1), survival decreased overall, and was higher for large-egged than small-egged siblings. Thus, contrary to conventional expectation, low oxygen levels selected for large rather than small eggs. A second experiment using Atlantic salmon (S. salar) eggs indicated that oxygen consumption increases relatively slowly with increasing egg mass (allometric constant = 0.44). The failure of the conventional 'bigger is worse during incubation' hypothesis may thus be due to the erroneous assumption that oxygen consumption increases at a greater rate with increasing egg mass than does the egg surface area that is available for oxygen diffusion. We also demonstrate, using data from Atlantic salmon, that nest-specific oxygen consumption decreases with increasing egg size, but that this effect is more pronounced for large than for small females. This may help to explain the positive correlation between adult body size and egg size observed in fishes that cluster their eggs.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2002.2150