The dating of the ‘3R WGD’ [300 Mya (Taylor et al., 2003; Volff, 2005)] at the very basis of teleostean evolution, means that probably all teleostean lineages have, or at least once had, duplicate leptin genes. Indeed, we were able to identify a leptin-a and leptin-b gene in medaka, a species whose evolutionary lineage separated Mya (Hoegg and Meyer, 2005) from the cyprinid lineage of zebrafish and common carp, an observation that confirms this notion and anchors the leptin duplication very
early in teleostean evolution