Developing artificial mixed diets for larval culture of sea cucumber, Holthuria leucospilota, and their effects on the internal microbiota

Abstract

During the seedlings culture of sea cucumbers including Holthuria leucospilota, natural microalgae are generally used as ideal food for the pelagic larvae of sea cucumbers, which lead to a strong demand for microalgae production. However, microalgae production is time-consuming and laborious and susceptible to pests and variable whether, and unstable supply of microalgae often results in culture failure of sea cucumber larvae. In this study, we tested the effect of three different diets on the growth, survival rate, and internal microbiota composition of sea cucumbers aiming to develop an artificial diet for H. leucospilota larvae. The results showed that the sea cucumber larvae fed with the mixed artificial diet (composed of Sargassum powder, chilled macroalgae solution, wall-breaking Chlorella powder, and yeast powder) had the most balanced growth rate, highest survival rate, and a higher α-diversity and abundance of Plesiocystis, Haloferula, and Firmicutes in body when they were compared to the larvae fed with the natural bait, Chaetoceros muelleri. However, the abundance of potential pathogenic bacteria, Francisella and Acinetobacter, was higher in the larvae fed with the natural bait. In conclusion, the mixed artificial diet was developed for H. leucospilota larval culture, which can be used as a good alternative to live microalga with cumbersome processes.