Paradoxical frog species has tadpoles that are larger than adults

Paradox frogs are only about 8 cm long, while in the tadpole stage they can be up to 22 cm long.

The adult paradox frog is smaller than its tadpole self. Photo: Minden Pictures — The adult paradox frog is smaller than its tadpole self. Photo: *Minden Pictures*

The paradox frog ( Pseudis paradoxa ), also known as the miniature frog, is found in northern South America and Trinidad. It feeds on invertebrates, primarily insects. This may sound like common sense, but it is not like other frogs. This strange creature shrinks in size as it grows.

In their larval stage, they are significantly larger than their adult stage. Specifically, the tadpoles of the paradox frog are three to four times larger than the adults. While tadpoles can grow up to 22 centimeters long, the adult frogs are only 8 centimeters long. Several other species in the genus Pseudis also undergo this unusual size change, but the paradox frog holds the record for having the longest tadpoles.

Adult paradoxical frog and tadpole models in the Natural History Museum, London. Photo: Chipmunkdavis — Adult paradoxical frog and tadpole models in the Natural History Museum, London. Photo: *Chipmunkdavis*

So why are tadpoles of the paradox frog so large? According to a 2009 study published in The Herpetological Journal , tadpoles grow at the same rate as other species, but they continue to grow and develop. By the time the tadpoles undergo metamorphosis into adult frogs, the males have begun producing sperm and the females are developing eggs—something that normally happens during the froglet stage.

In a study of another frog species in the genus Pseudis , experts studied the skeletal development of tadpoles of that species and found that the skeleton was nearly fully developed or fully developed by the end of metamorphosis.

The tadpoles' enormous size is mainly due to their long tails. Before metamorphosis into adults, their length from mouth to anus (or body length) is also equivalent to that of adults.

In most frogs, after metamorphosis, the frog starts out small but then gets larger. However, because the tadpoles of the paradox frog develop over a longer period of time than other species and are already quite complete when they go through metamorphosis, the adults grow little or not at all. The loss of the tail causes the frog to shrink in size.

Thu Thao (According to Live Science )

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