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The evolutionary puzzle of egg size, oxygenation and parental care in aquatic environments
Univ Zurich, Inst Evolutionary Biol & Environm Studies, Anim Behav, CH-8057 Zurich, Switzerland.;Univ Gothenburg, Dept Biol & Environm Sci, S-40530 Gothenburg, Sweden..
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
Univ Gothenburg, Dept Biol & Environm Sci, S-40530 Gothenburg, Sweden..
2015 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 282, no 1813, 20150690Article in journal (Refereed) Published
Abstract [en]

Offspring fitness generally improves with increasing egg size. Yet, eggs of most aquatic organisms are small. A common but largely untested assumption is that larger embryos require more oxygen than they can acquire through diffusion via the egg surface, constraining egg size evolution. However, we found no detrimental effects of large egg size on embryo growth and survival under hypoxic conditions. We tested this in the broad-nosed pipelish, Syngnathus typhle, whose males provide extensive care (nourishment, osmoregulation and oxygenation) to their young in a brood pouch on their bodies. We took advantage of this species' pronounced variation in egg size, correlating positively with female size, and tested the effect of hypoxia (40% dissolved oxygen) versus fully oxygenated (100%) water on embryo size and survival of large versus small eggs after 18 days of paternal brooding. Egg size did not affect embryo survival, regardless of O-2 treatment. While hypoxia affected embryo size negatively, both large and small eggs showed similar reductions in growth. Males in hypoxia ventilated more and males with large eggs swam more, but neither treatment affected their position in the water column. Overall, our results call into question the most common explanation for constrained egg size evolution in aquatic environments.

Place, publisher, year, edition, pages
2015. Vol. 282, no 1813, 20150690
Keyword [en]
egg size, embryo survival, fish, hypoxia, paternal care, Syngnathidae
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URN: urn:nbn:se:uu:diva-265931DOI: 10.1098/rspb.2015.0690ISI: 000362050000010OAI: oai:DiVA.org:uu-265931DiVA: diva2:866962
The Royal Swedish Academy of SciencesSwedish Research Council
Available from: 2015-11-04 Created: 2015-11-04 Last updated: 2015-11-20Bibliographically approved

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Ahnesjö, Ingrid
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Animal ecology
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