Egg size does not universally predict embryonic resources and hatchling size across annual killifish species

Abstract

24Egg size has a crucial impact on the reproductive success of a mother and the performance of 25 her offspring. It is therefore reasonable to employ egg size as a proxy for egg content when studying 26 variation in offspring performance. Here, we tested species differences in allometries of several egg 27 content parameters with egg area. We measured individual eggs in five species of annual killifish 28 (Cyprinodontiformes), a group of fish where egg banks permit population survival over dry season. 29Apart from comparing allometric scaling exponents, amounts and compositions of egg components 30 across the different species, we assessed the explanatory power of egg area for egg wet and dry weight 31 and for hatchling size. We found notable species-specific allometries between egg area and the other 32 egg parameters (egg dry weight and water content, elemental composition and triglyceride content). 33Across species, egg area predicted egg wet weight with highest power. Within species, coefficients of 34 determination were largest in Austrolebias elongatus, a large piscivorous species with large eggs. Our 35 study shows that systematically using egg area as a proxy of egg content between different species 36 can ignore relevant species-specific differences and mask within-species variability in egg content. 37 38