Monday, 15 December 2014

The Paradoxical Shrinking Frog

Pseudis paradoxa in a pond
Credit: Mauricio Rivera Correa
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Hylidae
Genus: Pseudis
Species: Pseudis paradoxa
Common Name(s): Paradoxical frog or Shrinking frog
Conservation Status: Least Concern (Not Threatened)

Looks like a pretty much regular frog, doesn't it? Well.. it's not! Meet P. paradoxa, a frog that grows down instead of growing up!

Confused? So were the scientists when they first discovered it. The species begins its life like most frogs do, as a tadpole. A big tadpole that is, up to 25 cm long. But then something weird happens. It morphs into an actual frog that is only about a quarter of its former length! Not surprisingly, the species became known as the shrinking frog.

Distribution & Habitat
The paradoxical frog is an aquatic species that inhabits ponds, lakes and lagoons from northern Argentina, through the Pantanal, Amazon and the Guianas, to Venezuela and Trinidad, with a disjunct distribution in the Magdalena River watershed in Colombia and adjacent far westfern Venezuela.

Sexually matured adults are usually 4,5 to 6,5 cm long, but can reach sizes of up to 7,5 cm. The head is relatively small compared to the body, with a short and round snout. The iris is yellow with a transverse brown bar. The body is primarily green with dark green to olive green stripes and the skin is slippery.

As aforementioned, P. paradoxa is unique in that the tadpole stage is 3 to 4 times larger than the adult form, reaching sizes of up to 22 cm. . Sexual dimorphism in the tadpole and adult stage is apparent, with females being larger than males.

In captivity they have been reported to live for 11 years.

Comparison between adult and tadpole stage
Credit: By Chipmunkdavis, via Wikimedia Commons

The species is nocturnal and spends its life almost exclusively in the water, usually hidden below the surface near floating plants.

Diet & Predators
Paradoxical frogs feed on insects like dragonflies and other smaller sized frogs and amphibians.

Paradoxical Frog Quacking

The mating season is probably the only time these weird animals become active during the day. During this period, the males start calling for the females and then mount them.

The females then lay their eggs among water plants; the eggs later develop into giant tadpoles. The hatchlings grow to become greenish tadpoles.

Paradoxical frogs breeding
Sexy Time!
By Felipe Gomes, via Wikimedia Commons

Conservation Status
The paradoxical frog has a widespread distribution and a seemingly high tolerance for a broad range of habitats. Adding to this a presumably large population and no major threats, it has been classified by the IUCN as Least Concern.

Some minor threats for the species include habitat loss due to agricultural activities and human settlement.

Other Interesting Facts about the Paradoxical Frog
- In March 2008, researchers working at the Universities of Ulster and United Arab Emirates released findings of a study where the synthesized version of the compound pseudin-2 [naturally occuring in the skin of the paradoxical frog] was able to stimulate the secretion of insulin in pancreatic cells under laboratory conditions, without toxicity to the cells. This synthetic medicine has possible applications in the treatment of Type 2 diabetes. Pseudin compounds are believed to have antimicrobial functions in the paradoxical frog.

More Strange Frogs

References & Further Reading
- EMERSON, S. (1988). The giant tadpole of Pseudis paradoxa Biological Journal of the Linnean Society, 34 (2), 93-104 DOI: 10.1111/j.1095-8312.1988.tb01951.x
- Abdel-Wahab YH, Power GJ, Ng MT, Flatt PR, & Conlon JM (2008). Insulin-releasing properties of the frog skin peptide pseudin-2 and its [Lys18]-substituted analogue. Biological chemistry, 389 (2), 143-8 PMID: 18163889
- Arias, M., Peltzer, P., & Lajmanovich, R. (2002). Diet of the giant tadpole Pseudis paradoxa platensis (Anura, Pseudidae) from Argentina Phyllomedusa: Journal of Herpetology, 1 (2) DOI: 10.11606/issn.2316-9079.v1i2p97-100
- Ariadne Angulo, Diego Baldo (2010). "Pseudis paradoxa". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 9 April 2012.

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