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Evaluation of coloration in koi carp (Cyprinus carpio var. koi) using CIELab and RGB techniques affected by dietary lysophospholipids and astaxanthin levels
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Arian Chalaki1   , Sakineh Yeganeh1 * , Batoul Adhami1 |
| 1-Department of Fisheries, Faculty of Animal Science and Fisheries, Sari Agricultural Sciences and Natural Resources University , skyeganeh@gmail.com |
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Abstract: (31 Views) |
Extended abstract
Introduction
Koi carp (Cyprinus carpio var. koi) is one of the most commercially valuable and popular ornamental fish species globally, renowned for its attractive appearance and cultural significance. The aesthetic appeal of Koi is primarily dictated by its skin coloration, which results from carotenoid pigments stored in chromatophores, specifically xanthophores and erythrophores. Since fish cannot synthesize carotenoids de novo, these pigments must be supplied via the diet. Astaxanthin, a potent keto-carotenoid, is widely recognized for enhancing red and orange pigmentation in fish. However, its absorption efficiency in the gastrointestinal tract is often a limiting factor due to its fat-soluble nature. Lysophospholipids (LPLs) are bioactive lipid compounds known to enhance the emulsification and absorption of dietary fats and fat-soluble nutrients by facilitating micelle formation in the gut. While the individual roles of astaxanthin and LPLs have been studied in various aquaculture species, their synergistic effect on the skin coloration of Koi carp remains unexplored. Therefore, this study aimed to investigate the efficacy of dietary supplementation with LPLs, combined with different levels of astaxanthin, on the skin colorimetric indices of C. carpio var. koi.
Materials and Methods
The study was conducted over 56 days (May to July 1404) at a private aquaculture facility. 150 Koi carp (initial weight: 3.63±0.05 g) were randomly distributed into 15 glass aquaria (60 L each) following a completely randomized design (5 treatments, 3 replicates, 10 fish/tank). Treatments included: (1) Control (basal diet); (2) 0.01% astaxanthin; (3) 0.02% astaxanthin; (4) 0.01% astaxanthin + 0.1% LPL; and (5) 0.02% astaxanthin + 0.1% LPL. Fish were fed three times daily at 5% body weight. Water quality parameters were maintained at optimal levels (26±1°C, pH 7±0.1). Skin color was measured using a Lovibond CAM-System 500. Indices including lightness (L), redness (a), yellowness (b), chroma, hue angle, and redness index (RI) were calculated according to standard CIE protocols. Statistical differences were analyzed via one-way ANOVA followed by Duncan’s multiple range test (p<0.05).
Results and Discussion
The results indicated that lightness remained unaffected by the dietary treatments (p>0.05). However, significant improvements were observed in other colorimetric indices. Astaxanthin-enriched diets significantly increased redness and yellowness compared to the control group (p<0.05). Importantly, the combination of 0.1% LPL with astaxanthin yielded the highest values for chroma and redness index, while simultaneously significantly decreasing the hue angle, indicating a shift toward a deeper, more vibrant red hue. The control and 0.01% astaxanthin-only groups exhibited the lowest chroma, suggesting that dietary pigment levels alone were insufficient for optimal saturation without emulsification support. The enhanced performance in LPL-supplemented groups confirms the synergistic effect of LPLs in optimizing lipid metabolism and promoting the bioavailability of astaxanthin. By improving micelle formation and reducing surface tension in the digestive tract, LPLs facilitated more efficient absorption and subsequent deposition of astaxanthin in the skin chromatophores. These findings align with previous reports on shrimp and other fish species, where LPLs served as biological emulsifiers to maximize carotenoid utilization. The study demonstrates that LPLs effectively break the absorption barrier, ensuring that high-cost pigments like astaxanthin are utilized efficiently rather than excreted, thereby significantly improving the commercial quality and color vividness of Koi carp.
Conclusion
This study concludes that dietary astaxanthin is essential for the pigmentation of Koi carp, but its utilization is significantly optimized by the co-supplementation of lysophospholipids. The synergistic interaction between astaxanthin and LPLs enhances the bioavailability of carotenoids, resulting in superior color saturation (chroma) and desirable red tone (hue) compared to astaxanthin supplementation alone. This nutritional strategy not only improves the marketability and aesthetic value of ornamental Koi carp but also offers an economically viable approach to reducing pigment wastage in aquaculture. Further research is recommended to explore the molecular mechanisms of pigment deposition in Koi skin under varying LPL concentrations and long-term storage conditions. |
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| Keywords: Astaxanthin, Lysophospholipid, Koi carp, Colorimetry, CIELab technique |
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Type of Study: Research |
Subject:
Special
Received: 2026/05/20 | Accepted: 2026/05/27
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