Effects of different diets on Strongylocentrotus intermedius feeding, growth and chondroitin sulfate accumulation

【Objective】To clarify the effects of Saccharina japonica, Gracilaria verrucosa and Ulva lactuca on the feeding, shell diameter growth, body weight growth, gonadal color and chondroitin sulfate accumulation in the sea urchin Strongylocentrotus intermedius. Additionally, to provide a theoretical basis and new clues for the screening of suitable diets and developing reasonable breeding strategy for cultured S. intermedius during fresh diets shortage period.【Method】The S. intermedius were divided into S. japonica feeding group, G. verrucosa feeding group and U. lactuca feeding group according to the feeding bait, and on the 30^th, 60^th and 90^th d after feeding, the vernier calipers were used to determine the shell diameter and shell height of S. intermedius, and the balance was used to determine the body weight and gonad weight, and the average daily feeding rate, diet coefficient, growth rate of shell diameter, specific growth rate, and the gonad index were calculated, and the chondroitin sulfate content of S. intermedius gonad and the activity of chondroitin sulfate synthase were determined by enzyme-linked immunoassay(ELISA). 【Result】As feeding time progressed, average daily feeding rate of S. intermedius in each experimental group showed a generally downward trend. The average daily feeding rate of S. intermedius in G. verrucosa feeding group was the highest, followed by the S. japonica feeding group, and the average daily feeding rate of S. intermedius in U. lactuca feeding group was the lowest. In each time period, the highest diet coefficient was in the G. verrucosa feeding group, followed by the S. japonica feeding group, and the lowest was in the U. lactuca feeding group, and there were significant differences among the three groups(P<0.05, the same below). The shell diameter growth rate and specific growth rate of S. intermedius showed a decreasing trend with feeding time passed, and at the same feeding time, there were significant differences in the shell diameter growth rate and specific growth rate among treatment groups, with the order being S. japonica feeding group >U. lactuca feeding group >G. verrucosa feeding group. There were some differences in the gonadal index of S. intermedius among the three treatment groups, in the order of S. japonica feeding group >U. lactuca feeding group >G. verrucosa group, and the gonadal color of S. intermedius was superior in G. verrucosa feeding and S. japonica feeding groups. The gonadal redness was the highest at all feeding times in the G. verrucosa feeding group, and gonadal yellowness was significantly higher in the G.verrucosa feeding group than in the rest of the treatment groups at the 90th d, while the difference in gonadal bright yellow coloration was the lowest in the S. japonica feeding group at all feeding time. Chondroitin sulfate content and chondroitin sulfate synthase activity in the gonads of S. intermedius were the lowest in the G. verrucosa feeding group. There were no significant differences between the S. japonica and U. lactuca feeding groups(P>0.05). 【Conclusion】Different diets have different effects on the feeding, shell diameter growth, body weight growth, gonadal development and quality, and chondroitin sulfate accumulation of S. intermedius, which can be effectively supplemented by feeding U. lactuca and G.verrucosa during the period of S. japonica scarcity to ensure the growth and development of S. intermedius.