Lizard Embryos Prioritize Posthatching Energy Reserves over Increased Hatchling Body Size during Development

Area of Science:

• Reproductive Biology
• Developmental Biology
• Ecology

Background:

• Embryonic development in egg-laying (oviparous) organisms relies on yolk reserves.
• Residual yolk remaining at hatching can support early posthatching life.
• Larger offspring size at hatching may confer advantages in growth and survival.

Purpose of the Study:

• To investigate the trade-off between residual yolk quantity and offspring size at hatching in lizards.
• To determine if embryos prioritize yolk exhaustion for larger size or yolk retention for posthatching support.
• To analyze the impact of experimentally reduced yolk on neonatal size and residual yolk.

Main Methods:

• Experimental manipulation of yolk quantity in lizard eggs (Amphibolurus muricatus) at oviposition.
• Quantification of offspring size (neonatal size) at hatching.
• Measurement of the amount of internalized residual yolk in hatchlings.

Main Results:

• Eggs with experimentally reduced yolk produced smaller offspring compared to controls.
• The proportion of residual yolk in yolk-reduced offspring was similar to that of unmanipulated offspring.
• This indicates that embryos retained a similar proportion of yolk reserves regardless of initial yolk availability.

Conclusions:

• The findings support the scenario where embryos reduce neonatal size by retaining yolk reserves at hatching.
• The fitness benefits of posthatching energy stores (residual yolk) appear to outweigh the benefits of larger neonatal size.
• This suggests a strategic allocation of resources favoring early posthatching survival in this species.