title: Extreme intra-clutch egg size dimorphism is not coupled with corresponding differences in antioxidant capacity and stable isotopes between eggs.
abstract: Oviparous females need to allocate resources optimally to their eggs in order to maximize their fitness. Among these resources, dietary antioxidants, acquired by females and transferred to the eggs during egg formation, can greatly affect the development and survival of the embryo and chick. In crested penguins, incubation starts after the second and last egg is laid and, as opposed to many other bird species, this egg hatches first, thereby enhancing the survival of the chick. Here, we assessed whether antioxidant and isotopic composition could underlie these differences between eggs within clutches of southern rockhopper penguins (Eudyptes chrysocome chrysocome). The second-laid egg had higher total antioxidant capacity than the first-laid egg, although this was not due to higher antioxidant concentration but to its higher mass. This suggests that resources are allocated by females at a constant rate in both eggs within clutches. Accordingly, we found a strong correlation for isotopic compositions between eggs suggesting that resources were allocated similarly to each egg within the clutch. Overall, we found little evidence for a significant role of antioxidant and isotopic compositions to explain differences in terms of embryo/chick development between eggs in crested penguins. However, since our results suggest a constant rate of antioxidant transfer from females to eggs, limiting the mass of the first-laid egg might represent a strategy for females to spare antioxidant defences and preserve self-maintenance.
authors.affiliation: Behavioural Ecology & Ecophysiology Group, Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Antwerp (Wilrijk), Belgium. Electronic address: maud.poisbleau@gmail.com.
authors.forename: Maud
authors.initials: M
authors.lastname: Poisbleau
authors.affiliation: Zoological Institute and Museum, University of Greifswald, Johann-Sebastian Bach Str. 11/12, 17489 Greifswald, Germany.
authors.forename: Michaël
authors.initials: M
authors.lastname: Beaulieu
authors.affiliation: Behavioural Ecology & Ecophysiology Group, Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Antwerp (Wilrijk), Belgium.
authors.forename: Nina
authors.initials: N
authors.lastname: Dehnhard
authors.affiliation: Behavioural Ecology & Ecophysiology Group, Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Antwerp (Wilrijk), Belgium.
authors.forename: Laurent
authors.initials: L
authors.lastname: Demongin
authors.affiliation: Laboratory of Oceanology, FOCUS UR, University of Liège, B6C, 4000 Liège, Sart Tilman, Belgium.
authors.forename: Gilles
authors.initials: G
authors.lastname: Lepoint
authors.affiliation: Laboratory of Oceanology, FOCUS UR, University of Liège, B6C, 4000 Liège, Sart Tilman, Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sturaro
authors.affiliation: Behavioural Ecology & Ecophysiology Group, Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Antwerp (Wilrijk), Belgium.
authors.forename: Marcel
authors.initials: M
authors.lastname: Eens
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D001835:Body Weight; D002247:Carbon Isotopes; D048429:Cell Size; D052284:Clutch Size / Q000502:physiology; D005260:Female; D009587:Nitrogen Isotopes; D052287:Oviparity / Q000502:physiology; D010058:Oviposition / Q000502:physiology; D010063:Ovum / Q000166:cytology* / Q000378:metabolism*; D046429:Spheniscidae / Q000196:embryology / Q000254:growth & development / Q000502:physiology*
chemical_list: D000975:Antioxidants; D002247:Carbon Isotopes; D009587:Nitrogen Isotopes
keywords: Antioxidant capacity; Crested penguins; Female condition; Maternal transfer; Oxidative status; Stable isotope