Evidence of a new toxin in the red-tide dinoflagellate Prorocentrum minimum

Several clones of Prorocentrum minimum were isolated from various French Mediterranean and English Channel sites. Mouse tests performed using methanolic extracts from cultures revealed a neurotoxic activity in four clones. The water-soluble toxin detected worked rapidly, killing mice within a few minutes at high doses. Toxin production in cultures was observed during the phase of decline and appeared to be weak or nil during the growth phase. Toxin production was stimulated by associated bacteria in the culture, but a clone rendered axenic remained able to produce toxins. The potential risks of human poisoning from consumption of shellfish harvested during or after toxic blooms of P.minimum are discussed.