The first melatonergic receptor was cloned from melanophores of "Xenopus laevis" in 1994. They induced shedding in Xenopus laevis by adding the excitatory amino acid L-aspartate. "Xenopus laevis" is a rather inactive creature. But is also found in the African clawed frog ("Xenopus laevis"). Rsk was first identified in "Xenopus laevis" eggs by Erikson and Maller in 1985. Xenbase is the Model Organism Database (MOD) for both "Xenopus laevis" and "Xenopus tropicalis". The first vertebrate animals to be mapped in this way were Zebrafish and "Xenopus laevis". In "Xenopus laevis", Cyr61 is required for normal gastrulation and modulation of Wnt signaling. Expression of "mct8" has been characterised in "Xenopus laevis" and "Xenopus tropicalis". Genetically modified frogs, in particular "Xenopus laevis" and "Xenopus tropicalis", are used in development biology.