and a medaka leptin receptor mutant (Chisada et al., 2013). One could regard the latter model as a teleostean equivalent of the famous db/db mouse model. In the hypothalamus of this lepr/ mutant orexigenic signals npy and agrp were constantly up- regulated, whereas pomc1 expression was down-regulated. Mutant medaka were characterised by higher feed intake in both post-juveniles and adult
fish. Interestingly, this increase in food intake corresponded with a higher growth rate at the post-juvenile stage, but did not change adult body size (Chisada et al., 2013). Perhaps even more striking is that this mutant medaka is characterised by increased visceral fat deposition, whereas fat content of liver and muscle did not change.