The temporal dynamics of bacteria in the coelomic fluid of sea cucumber Apostichopus japonicus after evisceration

Sea cucumbers have been emerged as important models to study organ regeneration and development owing to the capacity to regenerate its organs quickly after evisceration. Evisceration is a special defense mechanism for sea cucumber to eject all of internal organs when they encounter predators or adverse environmental conditions. However, little was known about the dynamics of bacterial community in coelomic fluid after evisceration. In the present study, evisceration was induced by intracelomic injection of 0.35 M KCl, and the significantly alternation of bacterial community in coelomic fluid of sea cucumber Apostichopus japonicus was observed with lower diversity and total bacterial load at 7 dpe (days post evisceration) and 14 dpe. The bacterial community was tended to restore at 28 dpe. In particular, relative abundances of Bacteroidetes and Rubritaleaceae, which involved in degradation of polysaccharides and lipid, increased significantly at 7 dpe (p < 0.05), and returned to the original level at 28 dpe. In addition, the predicted functions of bacterial community indicated that the bacteria associated with metabolism pathways of amino acid, lipid and carbohydrate also increased significantly at 7 dpe. These results suggested that the bacterial community in coelomic fluid of A. japonicus was highly dynamic and could rebuild a stable community structure after evisceration. It was suggested that the enriched metabolic related beneficial bacteria at early stage played a role after evisceration in terms of decomposing polysaccharides and lipid to provide energy.