| Popis: |
Sex-biased resource allocation in eggs is increasingly recognized as one strategy oviparous mothers can employ to invest diff erentially in one sex, depending on nutritional requirements. Previous studies have used egg size as an index of nutrient allocation, but few have examined egg contents directly. We used molecular sexing of early-stage ring-billed gull Larus delawarensis embryos, a species with sexual size dimorphism, to test whether sex-specifi c nutrient allocation occurs in ovo. Despite no sex diff erence in size, eggs with male embryos contained more albumen, while eggs with female embryos contained more yolk, lipid and non-lipid (protein and carbohydrate). It is unclear why such sex-biased resource allocation in ovo is utilized by ring-billed gulls. However, our data indicate that a cursive examination of egg mass or size may not necessarily refl ect nutrient allocation strategies mothers use in ovo, and that sex-biased investment in ovo may be more widespread than currently appreciated. |
