Although the addition of carotenoid in diet promotes
a reddish coloration, the cultured red porgy
still displays a darker colour unlike wild specimens,
which have a pink and silver colour on the dorsolateral
surface of their skin.Thismight be because of the
high melanin content and/or the low or wrong type
of carotenoids in the skin. Melanin, which is synthesized
from tyrosine and whose main function is
photoprotection, could be overproduced as a physiological
response of ¢sh to culture conditions as a result
of the exposure to high-intensity sunlight or
stress imposed by aquaculture practices. Cultured
red porgy apart from being exposed to ultraviolet
(UV) light received protein-rich diets, whichmay promote
melanogenesis because of their high tyrosine
content. In addition, the lack of dietary carotenoids
may further enhance melanogenesis, as carotenoids
are known to prevent oxidative stress. To get a better
understanding on the nutritional regulation of skin
colour in red porgy, towards the development of a
natural hue in the reared population, the present
study aims (a) to investigate the e¡ectiveness of three
carotenoids, namely astaxanthin, b-carotene and lycopene
in improving red skin coloration, and (b) to
identify whether the protein/carbohydrate ratio of
the diet a¡ects melanin formation in the skin.
Although the addition of carotenoid in diet promotesa reddish coloration, the cultured red porgystill displays a darker colour unlike wild specimens,which have a pink and silver colour on the dorsolateralsurface of their skin.Thismight be because of thehigh melanin content and/or the low or wrong typeof carotenoids in the skin. Melanin, which is synthesizedfrom tyrosine and whose main function isphotoprotection, could be overproduced as a physiologicalresponse of ¢sh to culture conditions as a resultof the exposure to high-intensity sunlight orstress imposed by aquaculture practices. Culturedred porgy apart from being exposed to ultraviolet(UV) light received protein-rich diets, whichmay promotemelanogenesis because of their high tyrosinecontent. In addition, the lack of dietary carotenoidsmay further enhance melanogenesis, as carotenoidsare known to prevent oxidative stress. To get a betterunderstanding on the nutritional regulation of skincolour in red porgy, towards the development of anatural hue in the reared population, the presentstudy aims (a) to investigate the e¡ectiveness of threecarotenoids, namely astaxanthin, b-carotene and lycopenein improving red skin coloration, and (b) toidentify whether the protein/carbohydrate ratio ofthe diet a¡ects melanin formation in the skin.
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