Effect of the toxic dinoflagellate Alexandrium minutum on the copepod Euterpina acutifrons
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The effects of Alexandrium minutum strains with differing toxin contents on the pelagic harpacticoid copepod Euterpina acutifrons were studied. In small volume experiments (350ml), both strains strongly reduced naupliar activity (defined as movement) to 70% of the individuals after 24h of exposure. A considerable proportion of teh copepodetes and adult females (producing viable eggs) survived all five days of the experiment. Inactivation of nauplii was also observed in medium volume experiments (6 l), reaching 50% after 3 days of exposure to the more toxic strain. In large volume experiments (20 l), 10-15% of females were inactive after 1-2 days of exposure to concentrations of 10-3 cells ml-1 of both strains and of 10-4 cells ml-1 of the most toxic strain. The very low values of animal toxicity obtained by HPLC analysis of the copepods indicate that Euterpina did not feed actively on the algae. The cell-free filtrate from A. minutum (most toxic strain) cultures also had a deleterious ...