Effects of Various Natural Diets on Gonad Development, Roe Quality, and Intestinal Microbiota of the Purple Sea Urchin (Heliocidaris crassispina)

The study analyzed the impact of different diets on the gonadal development of sea urchin Heliocidaris crassispina. Kelp (Laminaria japonica), corn (Zea mays), carrots (Daucus carota), and sweet potatoes (Ipomaea batatas) were used to continuously feed adults of H. crassispina for 50 days. Results indicated that sea urchins fed with kelp had the highest weight gain rate (p<0.05), followed by those fed with sweet potato, no significant difference in weight gain rate was observed between other diets and no feeding groups (p >0.05). H. crassispin fed with corn had a significantly enhancing GSI (gonadsomatic index) (p<0.05), followed by those fed kelp, and no significant difference between the other diet groups, but their weight gain rate was higher than that of the no feeding group (p >0.05). While there was no significant difference in shell diameter and height in any diets (p >0.05). Sweet potatoes and corn significantly improved the redness (a∗) and yellowness (b∗) of the gonads (p<0.05). Kelp group and corn group had excellent performance in amino acid composition, containing higher levels of umami and sweet amino acids than other groups (p<0.05). Fatty acid analysis showed higher contents of eicosapentaenoic acid (EPA), arachidonic acid (ARA), linolenic acid, and linoleic acid in kelp and corn group. The types of diets significantly affected the microbial diversity of the digestive tract, with kelp enhancing microbial community diversity, and diets of corn and sweet potatoes increasing the abundance of Lactococcus. In conclusion, kelp was an excellent feed for H. crassispina, and corn as a preferred alternative diet not only improved the GSI but also optimized the gonad color and increased the content of amino acids and fatty acids.