Japanese Wrinkled Frog

Fascinating facts about the Japanese Wrinkled Frog

• The Japanese wrinkled frog was introduced to Hawaii in the late 19th century and has rough, uneven skin.
• In some Japanese rivers the same frog species uses male (XX/XY) chromosomes, while in others females carry ZW chromosomes. Two completely different sex-determination systems coexist within a single species, offering a living laboratory for how sex chromosomes evolve. It reminds us that nature can rewrite fundamental genetic rules right under our feet.
• Genetic maps split the frog’s population into eastern and western lineages so deep that scientists suspect hidden species lurking under the name G. rugosa. Those hidden divisions hint that what looks like one common frog may actually be several cryptic cousins. It teaches us that biodiversity can hide in plain sight, waiting for DNA to expose it.
• The frog’s habitats include rice paddies, ponds, streams, and other small freshwater spots across most of Japan, and it is listed as Least Concern on the IUCN Red List.
• Studies of its chromosomes reveal repeated “recycling” events where the same ancestral pair splits and reforms through recombination and hybridization.

At a glance

About the Japanese Wrinkled Frog

The Japanese wrinkled frog (Glandirana rugosa) has rough, uneven skin and is native to Japan, having been introduced to Hawaii in the late 19th century. It lives and breeds in various freshwater environments, including ponds, streams, wetlands, and rice paddies, and is listed as Least Concern on the IUCN Red List. Populations across Japan exhibit two different sex-determination systems, male heterogamety (XX/XY) in some regions and female heterogamety (ZZ/ZW) in others, making the species a model for studying the evolution and turnover of sex chromosomes in vertebrates.

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