The hemolytic activity of Karenia selliformis and two clones of Karenia brevis throughout a growth cycle

Blooms of the toxic dinoflagellate, Karenia brevis, occur annually along the Gulf coast of Florida. Other species, like Karenia selliformis, are at times found in association. Hemolytic activity, the ability to lyse red blood cells, of two K. brevis clones (SP3 non-toxic (N-tox) and SP3 super toxic (S-tox)) from the Gulf of Mexico and a single clone of K. selliformis from New Zealand was investigated throughout a growth cycle. Activity is reported as effective concentration (EC₅₀) values, the quantitative measure of hemolysis of human erythrocytes expressed as cell numbers. Both cells and media of K. selliformis cultures consistently produced potent levels of hemolysis (maximum EC₅₀ = 4.88 × 10³ cells) from inoculation until the population declined 35 days later. For SP3 N-tox and S-tox, no hemolytic activity was detectable until day 26 of sampling. The media of both SP3 N-tox and SP3 S-tox cultures consistently contained non-detectable or low levels of hemolysis compared to K. selliformis. Maximum EC₅₀s for the SP3 clones were 1.80 × 10⁶ and 1.97 × 10⁶ cells, respectively. The experimental EC₅₀ values observed represent ecologically relevant cell densities for K. selliformis, but not for the K. brevis clones. In addition, the hemolytic activity of gymnodimine A and various PbTx derivatives was examined in this study. Our findings indicate that the hemolytic capability of these dinoflagellates, especially K. selliformis, represents an additional component of toxicity aside from their already recognized toxins and that this activity may play a larger role than was previously considered. The purpose of this study was to extend the knowledge of the biology and toxicology of species within the genus Karenia.