The Main Skin Pigment Analysis And Effects Of Light In Skin Pigmentation Of Large Yellow Croaker (Poseudosciaena Crocea)

In this paper, major carotenoids and pigment cells in skin of large yellow croaker were studied withthe spectral and chromatographic technology.To study the regulation machanisms of light on shin color oflarge yellow croaker, the effects of light on skin color and pigment cells were observed.1.The microstructure characteristics of chromatophores in large yellow croaker were observed andrecorded through microscope. Four kinds of chromatophores were found: melanophore, xanthophore,erythrophore, guanophore. The nucleus of melanophore, which mainly distributed in the dorsal and scale, isrelatively larger than other chromatophores.The xanthophores containing yellow pigment granulesdistributed around the fish, and especially concentrated distribution in ventral. However, we founderythrophores only distributed in ventral. The guanophores contained guano granules and distributed inscales.2.The ventral and dorsal skin color and carotenoids content of cultured large yellow croaker(256.23±2.95g) between daytime and night were studied. The results showed that the brightness values (L*)were approximative, but the values in dorsal area were significantly lower than that in ventral; Thered/green values and blue/yellow values of skin color at night were higher than in the daytime, especially,the blue/yellow values in the dorsal were10.39and45.84in the daytime and at night respectively. Therewere two characteristic absorption between400-600nm. The total carotenoids of skin in large yellowcroaker at night were higher than that in the daytime.We all know that changes in the density andmorphology of pigment cells can induce morphological color changes in fish skin. To study the effects andregulation machanisms of light on shin color of large yellow croaker, we observed the movement ofpigment particles responsed to light stimulation. The results showed that UV and low wavelengths ofvisible light affected the pigment aggregation, and pigment dispersed induced by high wavelength ofvisible light, which darked pigment cells.4. The main pigment component in skin of large yellow croaker was detected using reversed-phasehigh performance liquid chromatography (RP-HPLC) with solid phase extraction SPE. The results showedthat lutein, accounting for50%, was the main pigment in skin of large yellow croake, which also containedlittle amounts of astaxanthin, canthaxanthin and other pigments. The linear relationship of this method forlutein, canthaxanthin and astaxanthin(R2>0.999) was excellent. The average spike recovery rates ofastaxanthin, canthaxanthin and lutein were85.61%94.37%,83.28%92.79%and84.26%96.56%withrelative standard deviations of2.55%5.78%,3.52%7.28%and3.026.55%respectively. The limit ofdetection was0.43mg/kg for lutein,0.59mg/kg for canthaxanthin,0.82mg/kg for astaxanthin.