The paradoxical frog: The unusual amphibian whose giant tadpole shrinks four times upon reaching adulthood

In the animal kingdom, the general rule of growth dictates that young creatures progressively increase in body volume until reaching maturity. However, in the wetlands and ponds of South America lives a creature that completely subverts this logic: Pseudis paradoxa, popularly known as the paradoxical frog.

During its aquatic larval stage, the tadpole of this species undergoes colossal development, reaching record dimensions of between 22 and 27 centimeters in length, a size equivalent to that of a young trout. Nevertheless, the astonishing part happens during the final phase of its metamorphosis: far from maintaining or expanding that size, the organism undergoes a drastic reduction. By reabsorbing its voluminous tail and reorganizing its skeleton, the final adult frog barely reaches between 5 and 7 centimeters, losing more than three-quarters of its original length.

This baffling life cycle bewildered eighteenth-century naturalists, including Carl Linnaeus himself. For years, European chroniclers held the erroneous theory that it was a reverse zoological process: frogs transforming into fish. In biological terms, the tadpole's massive tail acts as a huge reserve of carbohydrates and nutrients that fuels an express internal maturation driven by thyroid hormones.

In addition to its unusual physical shrinkage, this amphibian holds another scientific treasure: its skin secretions contain pseudin-2, an antibacterial compound that stimulates cellular insulin release, currently being investigated to develop treatments for type 2 diabetes.