Phylogenetic analysis of prepro-GnRHs in Phylum Chordata and Phylum Mollusca. The bootstrap values (in %) from 1000 replicas are given at each branch point. Prepro-GnRHs are clustered into five groups (GnRH-I to GnRH V). Each sequence is denoted by the name of its GnRH peptide form followed by the species from where it was isolated (in italics). Arabic numbers at the end of vertebrate sequences are used to indicate different precursors that encode the same GnRH peptide. Arabic numbers at the end of ciGnRH (tunicate) indicate different molecular forms of GnRH. The following abbreviations are used to denote the GnRH peptide forms: cGnRH-I (chicken GnRH-I), cGnRH-II (chicken GnRH-II), cfGnRH (catfish GnRH), ciGnRH (Ciona GnRH), gpGnRH (guinea pig GnRH), hrGnRH (herring GnRH), lGnRH-I (lamprey GnRH-I), lGnRH-III (lamprey GnRH-III), mGnRH (mammalian GnRH), pjGnRH (pejerry GnRH), sGnRH (salmon GnRH), sbGnRH (sea bream GnRH), and wfGnRH (whitefish GnRH).