The offspring of various animal species can resemble mini versions of their parents or look completely different before turning into the adult version. However, the paradoxical frog (Pseudis paradoxa) has a unique life cycle. Its tadpoles are three to four times larger than the final adult form, posing the question of what happens to all that tadpole?
The paradoxical frog holds the world record for the greatest size difference between tadpole and adult frog of the same species. The tadpoles can reach a maximum length of 16.8 centimeters (6.6 inches) before undergoing metamorphosis into adulthood, where they reach a size no more than 6.5 centimeters (2.5 inches). In some cases, the tadpoles may be as much as four times the size of the adults.
The genus Pseudis consists of 11 species, all of which live in Central and South America, including the Caribbean islands of Trinidad. A 2009 study compared the growth rate of paradoxical frog tadpoles with other tropical frog species and found that paradoxical frog tadpoles keep growing while other species begin to metamorphosize.
There are several theories about the drivers of this weird life history. Some suggest that the tadpoles mature faster into adults, while others believe that the adults eat higher-quality prey, restrict their growth rate, and spend more time out of water. Still, others suggest that the hormone prolactin may be responsible for the unusually large tadpoles. More research is needed to fully understand the paradoxical frog’s unique life cycle.