Pedomorphosis

Pedomorphosis is a term used in biology to describe the retention of juvenile or larval features in the adult form of an organism. This phenomenon can occur through several distinct evolutionary mechanisms, including neoteny, progenesis, and postdisplacement. Neoteny involves the slowing of somatic development relative to gonadal development, meaning the body matures slower than the reproductive organs. Progenesis, conversely, is the acceleration of reproductive development relative to somatic development, leading to sexual maturity while still in a larval or juvenile state. Postdisplacement refers to the delay of the onset of adult characteristics.

Pedomorphosis is observed across a wide range of taxa, from plants to animals. A classic example in the animal kingdom is the axolotl (Ambystoma mexicanum), a salamander that retains its external gills and aquatic lifestyle throughout its life, unlike most other salamanders which undergo metamorphosis to a terrestrial form. In some species of invertebrates, such as certain tunicates and insects, larval stages may become reproductively capable. The evolutionary significance of pedomorphosis is debated, but it is thought to provide adaptive advantages by allowing organisms to exploit new ecological niches or to survive in environments where metamorphosis is disadvantageous. It can lead to significant morphological divergence and is a key factor in evolutionary diversification.