 Most amphibians go through metamorphosis , a process of significant morphological change after birth . In typical amphibian development , eggs are laid in water and larvae are adapted to an aquatic lifestyle . Frogs , toads and salamanders all hatch from the egg as larvae with external gills . Metamorphosis in amphibians is regulated by thyroxine concentration in the blood , which stimulates metamorphosis , and prolactin , which counteracts thyroxine 's effect . Specific events are dependent on threshold values for different tissues . Because most embryonic development is outside the parental body , it is subject to many adaptations due to specific environmental circumstances . For this reason tadpoles can have horny ridges instead of teeth , whisker @-@ like skin extensions or fins . They also make use of a sensory lateral line organ similar to that of fish . After metamorphosis , these organs become redundant and will be reabsorbed by controlled cell death , called apoptosis . The variety of adaptations to specific environmental circumstances among amphibians is wide , with many discoveries still being made . 
