Effects Of 17α-Methyltestosterone And Carotinoids On The Pigmentation Of Aquarium Fish

Color is the main ornamental value of aquarium fish. In addition to water temperature, water quality, and illumination conditions, feed also has great influence on the body color of ornamental fish. Aquarium fish are fed with large amount of compound feed that is in deficiency of effective pigments compared with natural foods, and as a result, the color of aquarium fish is less colorful than its natural counterpart. The effect of pigmentation is obviously different when ornamental fish are fed with different coloring promoters. Carotinoid is one of the main coloring promoters for ornamental fish. . The study on the effect of feed additives such as carotinoids on the color of ornamental fish and the regularity of carotenoids deposition in different parts of fish were rarely reported.Methods for carotinoids extraction from the body of Xiphophorus helleri and its stability to light and temperature were established. The effects of dietary 17α-Methyltestosterone (17α-MT), astaxanthin, lutein,β- carotin on the body color of aquarium fish researched as follows.1. Extraction of pigment from Xiphophorus helleri and its stability to light and temperatureThe most effectively extracting condition of the carotenoids pigment content of fish was as follows: The best solvent was the mixture of acetone and petroleum ether (v/v=2 :1). The appropriate ratio between fish tissue and solvent was 1:70; The appropriate extraction time was 8 h. The extracted pigment has the maximum absorption at 448nm and was thermostable under temperature of 60℃or lower. The pigment was stable to natural light but unstable to ultraviolet light.2. The effects of 17α-Methyltestosterone on the colour of Brachydanio rerioDietary 17α-Methyltestosterone higher than 30mg/kg had significant effect on total carotenoids content of one-month-old Brachydanio rerio (p<0.05). The highest total carotenoids content of one-month-old Brachydanio rerio was 7.4156±0.8101 mg/100g at 50mg/kg dietary 17α-Methyltestosterone (p<0.05 ) . The highest total carotenoids content of one-month-old Brachydanio rerio fed with different amount of dietary 17α-Methyltestosterone was achieved on the 14^th day (11.8730±0.9575mg/100g, p<0.05).The total carotenoids content of three-month-old Brachydanio rerio fed with different amount of dietary 17α-MT on 56^th day were 4.3581±1.8293 mg/100g (treatment 1, 10mg/kg) , 4.6823±0.8763 mg/100g( treatment 2, 20mg/kg)and 3.2396±0.1842mg/100g(treatment 3, 30mg/kg) respectively, while that of treatment 4 (40mg/kg) and treatment 5 (50mg/kg) were 3.2238±0.7589 mg/100g and 3.1151±0.1784 mg/100g on 42^th day respectively. There were no significant differencesbetween all the treatments (p>0.05) .3. The effects of different ratio of 17α-Methyltestosterone and carotenoids on the color of Brachydanio rerio and Xiphophorus helleriFour factors (17α-Methyltestosterone, Astaxanthin, Lutein,β-carotene) each with 3 levels were designed as L9(3⁴) orthogonal table. One-month-old Brachydanio rerio, three-month-old Brachydanio rerio and three-month-old Xiphophorus helleri were fed for 56 days with designed diets as above. The result showed that, for one-month-old Brachydanio rerio, 17α-Methyltestosterone is the most important factor that influences the total carotenoids in fish body; astaxanthin and lutein are less important, andβ-carotin is the least. The optimal recipe was: 17α-Methyltestosterone 80mg/kg, astaxanthin 0～200mg/100g, lutein 200 mg/kg,β-carotin 100 mg/kg. For three-month-old Brachydanio rerio, 17α-Methyltestosterone is the most important factor that influences the total carotenoids in the body, astaxanthin andβ-carotin are less important, and lutein is the least.The optimal recipe was: 17α-Methyltestosterone 80mg/kg; astaxanthin 200 mg/kg, lutein 200 mg/kg,β-carotin 200 mg/kg. For three-month-old Xiphophorus helleri,β-carotenene is the most important factor that influences the total carotenoids content in the body, astaxanthin and lutein are less important, 17α-Methyltestosterone is the least. The optimum recipe was: 17α-Methyltestosterone 0 mg/kg, astaxanthin 100 mg/kg, lutein 100 mg/kg,β-carotin 100 mg/kg.4. Carotenoids deposition of aquarium fish in different body part and in different developmental stageDuring the experiment, the total carotenoids contents in different body part increased with prolonging of time. The major pigments deposition part of one-month-old Brachydanio rerio and three-month-old Brachydanio rerio were fins and body, while that of three-month-old Xiphophorus helleri were skin and fins.