Eukaryotic food sources analysis of two tropical sea cucumber species under different seasons providing insights into provender selection

Abstract

As the typical deposit-feeding organism, in the process of aquaculture, adult sea cucumbers usually feed on bioclasts in sediments under the artificial environment. Understanding feeding preference is one of the most essential parts for providing guidance for sea cucumber aquaculture. However, up to now, there have been few studies on the exact ingredients of these natural foods for holothurians, especially for tropical sea cucumbers. In present study, the eukaryotic composition of gut contents of two tropical sea cucumber species under enclosed waters of ponds, Stichopus monotuberculatus and Holothuria scabra, were investigated and compared with each other by high-throughput DNA sequencing. We also analyzed the variability of intestinal eukaryotic composition of the two sea cucumbers in different seasons (dry / wet seasons). The sequences of 18 S rRNA gene V4 region were amplified and a total of 2234 operational taxonomic units (OTUs) were obtained. S. monotuberculatus and H. scabra in dry season both fed mainly on Chlorophyta and Diatomea. In wet season, S. monotuberculatus fed mainly on Arthropoda and Diatomea, and H. scabra had a superior Ascomycota and Arthropoda concentrations. We found there were significant differences in eukaryotic composition of the same species between the wet season and dry season, and seasonal differences were higher than differences between species. Several eukaryotic organisms such as copepods Pseudodiaptomus nihonkaiensis were identified, whose related species as superior biological feed organisms have been successfully applied in aquaculture. These organisms may be considered as an additive feed for captive breeding of S. monotuberculatus. This study provides insights into provender selection for tropical sea cucumbers aquaculture.