Abstract

Unfavorable environments have a serious impact on sea cucumbers and even lead to diseases in aquaculture. Yellow intestinal disease has a serious effect on land-based aquaculture of sea cucumbers. This study is to clarify the effect of yellow intestinal disease on the behavior and gut health of sea cucumbers. We observed that feeding behavior significantly decreased in the sea cucumbers with yellow intestinal disease and that their righting response time was significantly longer compared to healthy individuals. Further, this study found that the heads of diseased sea cucumbers swung violently, and they preferred to stick to the wall of the tank rather than the bottom. This is contrary to sea cucumbers with enteritis disease. Additionally, we found that there was no significant difference in the thickness of the intestinal muscular layer between sea cucumbers with and without yellow intestine disease. However, the height of intestinal folds decreased, while the width significantly increased in diseased sea cucumbers. Novelly, the present study found that yellow intestinal disease did not change intestinal pepsin activity and flora abundance, although it reduced the feeding behavior of sea cucumbers and changed intestinal morphology. Yellow intestine disease is also different from the imbalance of intestinal microbiota caused by enteritis disease in sea cucumbers. Therefore, yellow intestine disease is probably not an enteritis disease, but a manifestation of sea cucumbers in the face of unfavorable environments. We suggest aquafarmers not treat sea cucumbers with yellow intestinal disease using the method to treat enteritis disease.