The effects of marigold as natural carotenoids on scale chromatophores’ variations in blue gourami under different stocking densities

Abstract

Skin coloration is important in ornamental fish. Fish coloration is due to the presence of chromatophores, which contain pigments and are usually located in dermis. In this study, the effects Marigold as natural carotenoids was investigated on fish scale chromatophores’ variations under different stocking densities. For this, diet containing 2.5% Marigold along with a control diet were fed to the fish held at two stocking densities of 20 and 30 fish (0.6 and 0.9 fish/Liter). After 70 d, changes in chromatophores were monitored in fish scales upper lateral line. The fish initial weight was 0. 80±0.02 g. Each treatment had three replications. According to the results, four different chromatophores, including Punctate, Punctate-stellate, Stellate, Stellate-reticulate were observed in the fish at the higher density. The results suggest that increase in stocking density alters chromatophores type and results in hypermelanosis that affects body surface and neural system; thus chromatophores indicate stress contamination.