Suitability of three seaweeds as feed in culturing strawberry conch Strombus luhuanus

Abstract

Our previous study showed that strawberry conch Strombus luhuanus could actively survive on seaweeds, such as Laminaria japonica, Eucheuma gelatinae and Undaria pinnatifida. In this study, four treatments, which included wild group and three seaweed-feeding treatment groups with L. japonica (L-D), E. gelatinae (E-D) and U. pinnatifida (U-D), were performed to evaluate the dietary value of these seaweeds as food source for strawberry conch. After 2-month of rearing period, strawberry conches that were fed with these seaweeds showed high survival rate and high increase in body weight. The specific growth rate (SGR) of strawberry conch of U-D treatment was the highest, followed by L-D and E-D treatments, with significant differences observed among three treatments (P < 0.05). The histological measurements, such as intestinal fold height (hF) and fold width (wF), enterocyte height (hE) and microvillus height (hMV) of intestinal tissues in U-D and L-D treatments were not lower than that of wild group, however, these measurements were found to be significantly lower in E-D treatment (P < 0.05). Moreover, amylase, cellulase and lipase activities in strawberry conches fed with seaweeds were higher than that in wild group, whereas contrasting result was observed for pepsin activities (P < 0.05). The concentrations of all amino acids, except methionine, histidine, serine and proline, were significantly higher in wild strawberry conch compared to seaweed-feeding groups (P < 0.05). The lipid contents in L-D and U-D treatments were no less than in wild group. However, n-3 polyunsaturated fatty acids (PUFA), especially docosapentaenoic acid (DPA), was significantly lower in all seaweed-cultured groups compared to wild individuals (P < 0.05). In summary, U. pinnatifida and L. japonica were found to be more suitable as diets than that of E. gelatinae for strawberry conch rearing.