Lizard embryos prioritize post-hatching energy reserves over increased hatchling body size during development

Abstract

Embryonic development in oviparous organisms is fueled by maternally-allocated yolk, with many organisms hatching before that energy store is completely used up; the resultant leftover (residual) yolk is internalized and may support early post-hatching life. We experimentally reduced yolk quantity at oviposition in lizard eggs (Amphibolurus muricatus) to determine if embryos (1) exhaust yolk supply during development (thereby maximizing neonatal size) or (2) reduce neonatal size by retaining yolk reserves at hatching. Our data support the latter scenario. Eggs from the yolk-reduced treatment produced smaller offspring with a similar proportion of residual yolk compared to offspring from unmanipulated eggs, suggesting that the fitness benefits of post-hatching energy stores outweigh those of larger neonatal size.