Water Frogs

• GeneralIt is a fertile hybrid between two green frog species, which is rare among vertebrates.
• It reproduces by hybridogenesis: when its gametes form it discards one of the two parental genomes, so that half its DNA is passed on cloned and intact.
• Two edible frogs can mate and lay eggs, but the larvae die: it needs to cross with one of the parent species in order to keep going.
• The name comes from its legs, eaten above all in France, Germany and Italy.
• It is not a species but a hybrid that breeds on its own. It arose from the cross between the pool frog and the marsh frog, and it perpetuates itself by hybridogenesis: it eliminates one of the two parental genomes from its germ cells and passes on only the other.
• That forces it to live alongside one of the parental species in order to reproduce, which is why it is regarded as a genetic parasite, or klepton. The abbreviation kl. in its name means precisely that.
• In some Swiss populations the extreme case has been found: populations made up solely of hybrids, which complete the cycle with no parental species present.
• In western Europe the system has been thrown off balance by the introduction of marsh frogs from other regions, which produce new hybrids, sometimes sterile, and threaten both the pool frog and the klepton itself.
• It is the frog whose legs are traditionally eaten in France, hence the name of edible frog.

Skeleton type

Vertebrate - internal bony skeleton (amphibian)

Habitat & environment

Ponds, canals and vegetated banks

Sources consulted: IUCN Red List (e.T76317591A87648183); Amphibian Species of the World (Frost, AMNH); Dubois 1992, Bulletin de la Société Linnéenne de Lyon 61; CITES CoP20 Prop. 27; Wikipedia (Edible frog)

Best time: From spring to summer, when it is most active; in winter it withdraws onto land to hibernate