Temporary cyst enables long-term dark survival of <Emphasis Type="Italic">Scrippsiella hangoei</Emphasis> (Dinophyceae)

We examined the dark survival strategy of the cold-water dinoflagellate Scrippsiella hangoei from the Baltic Sea. Cultures of S. hangoei were placed in dark and light and we followed the morphological developmentand, determined respiration rate and activity of extracellular leucine aminopeptidase (LAP). S. hangoei had LAP activity in the light, but not in the dark, suggesting that the degradation and use of organic substrates is not part of the dark survival strategy. After prolonged time in darkness (>5 days), S. hangoei started to shed flagella and theca, and produced a previously undescribed temporary cyst. The transformation from vegetative cell into the temporary cyst initially increased respiration rate tenfold, but after the transformation the respiration rate decreased to almost undetectable levels. The presented temporary cyst enables survival through long periods in dark by reducing the respiration rate.