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What is paedomorphosis in salamanders?

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Study an amphibious tiger salamander of the mole salamander family Ambystomatidae in its natural habitat — Caudata Tiger salamanders (*Ambystoma tigrinum*) are widespread across much of the United States. Although they are generally black with yellow blotches, bars, spots, or even stripes, some are lighter in colour or have olive markings. Tiger salamanders belong to the mole salamander family, Ambystomatidae.

In the context of the order Caudata, paedomorphosis is the retention of juvenile or larval traits by an organism into its adult, sexually mature phase.12

While most salamanders undergo a metamorphosis that transforms them from aquatic larvae into terrestrial adults, paedomorphic species bypass or only partially complete this process. As a result, these individuals retain larval characteristics—such as external gills—throughout their lives, even while they are capable of breeding.13

This condition is a specific form of heterochrony, which refers to changes in the timing and rate of developmental events. Paedomorphosis can be categorized into two primary aspects:3
* Progenesis: The acceleration of sexual maturation relative to the rest of the organism's development.2
* Neoteny: The retardation of bodily development relative to the onset of reproductive activity.2

Well-known examples of paedomorphic salamanders include the axolotl (Ambystoma mexicanum) and the mud puppy (Necturus maculosus), both of which retain gills and other larval structures as adults.13