Amphidinium species are amongst the most abundant benthic dinoflagellates in marine intertidal sandy ecosystems. Some Amphidinium species produce harmful cellular toxins or hemolytic toxins and can cause harmful benthic algal blooms. Amphidinols (AMs) are a class of polyketide compounds isolated from Amphidinium dinoflagellates. AMs possess antibacterial, antifungal activity, hemolytic activity, and cytotoxicity, and are also suspected of causing fish mortality. Among these, hemolytic toxins are considered a significant cause of fish mortality. In this study, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed to identify and quantify amphidinols (AMs) from available strains. The hemolytic activity of Amphidinium strains was detected by erythrocyte lysis assay. This study evaluated the hemolytic toxicity of six Amphidinium strains, including A.gibbosum, A.carterae, A. pseudomassartii, A.operculatum, A.massartii, and A.thermaeum. The results demonstrated that A.carterae was the most toxic species, while A.gibbosum and A.pseudomassartii did not exhibit significant hemolytic effects. We attempted to extract hemolytic toxins from the algal solution using a new method involving ethanol extraction of freeze-dried cell-free algal supernatant. The results indicated that the hemolytic toxins produced by A.carterae are secreted extracellularly. This study provided new information on the hemolysis-associated toxicities of the bioactive compounds produced by Amphidinium species, contributing to a better understanding of their emerging threats to marine fauna and enabling the development of monitoring tools for their blooms in the future.
 

dinoflagellate, Amphidinium, hemolytic toxin