How does the axolotl retain larval features as an adult?

The axolotl (Ambystoma mexicanum) retains its larval features, such as external gills, throughout adulthood through a biological process known as paedomorphosis.12

This phenomenon is a form of heterochrony, which refers to changes in the timing and rate of developmental events. In the case of the axolotl, the organism reaches sexual maturity while maintaining its juvenile or larval morphology. While most amphibians undergo a metamorphosis triggered by thyroid hormones to transition from an aquatic larval stage to an adult body plan, the axolotl’s development is arrested. This allows the species to remain aquatic and retain traits like its larval gills and fin structure even after it becomes capable of reproduction.23451

This evolutionary strategy is considered to have adaptive significance, as it allows the axolotl to thrive in its specific aquatic environment. Other salamanders, such as mud puppies and olms, also exhibit similar paedomorphic traits.32