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Targeted Species by LIFE CROAA

The LIFE CROAA program places particular emphasis on the control of two invasive alien species: the American bullfrog and the African clawed frog.

The American Bullfrog

The bullfrog (Lithobates catesbeianus) is a sizeable Anura that can be imposing (more than 25 cm and nearly a kilogram). With a typical frog-like appearance, but without dorso-lateral folds, it has a very large tympanum (especially in the male). His song, a kind of deaf mooing, earned him his name. Clutch size can be very important, with more than 20 000 eggs and the larvae often take at least a year before metamorphosing. They live in all kinds of water bodies, rather hot and often unnatural and permanent. Originally from North America, it is now introduced in more than 40 countries. Its introduction has often been voluntary, for its consumption, the leisure or biological control of insect pests, but also accidental, following escapes from breeding farms.

Its impact on native wildlife is clear, as it is a strong predator and competitor, which can participate in the decline of amphibians and local fish. It is a healthy carrier of Chytrids, Batrachochytrium dendrobatidis, a pathogenic fungus in Amphibians.

The African clawed frog

The African clawed frog (Xenopus laevis) is an anura from the Pipidae family, an Amphibian family without tongue and with very aquatic life. Xenopus have claws and live natively in sub-Saharan Africa in all kinds of water bodies (slow-moving rivers, ponds, marshes, puddles, reservoirs, ditches, etc.). The African clawed frog size up to 13 cm for females that are larger than males. It has an overall morphology very different from European species: its body is rather flat, its head small without eardrums, its skin smooth and quite slippery when grasped. Its tadpoles have two remarkable barbels next to the mouth.

It has been introduced in many countries: United States (11 states), Chile, Japan, the Netherlands, Sicily … You must know that the African clawed frog was used from the 1940s all around the world as a pregnancy test, after the discovery that a pregnant woman urine injection triggered the laying of the clawed frog. This very practical test, combined with a technically fairly simple and productive breeding, has participated in the presence of African clawed frog in many countries and locally its introduction, voluntary or accidental, in the natural environment. In addition, the species has also been sold as a recreational animal and is now the most widely used vertebrate species for scientific research in cell biology, molecular biology or development. It is therefore a very useful species for laboratory research.

On the other hand, the introduced populations are often very dynamic and invasive, and are a proven threat to many species of native wildlife. In Sicily, for example, its presence directly affects the densities and reproduction of some indigenous Amphibians (Lillo et al., 2010). It is a healthy carrier of Chytrids, Batrachochytrium dendrobatidis, pathogenic fungus in Amphibians.