AME 62:99-108 (2011)  -  DOI: https://doi.org/10.3354/ame01459

ABSTRACT: We verified an active uptake of kleptoplastids in the toxic and bloom-forming dinoflagellates of the genus Dinophysis from its preferred prey, the ciliate Myrionecta rubra, using a quantitative real-time PCR technique. During a 65 d starvation/feeding experiment with Dinophysis caudata, changes in plastid 16S rRNA, plastid autofluorescence and plastid/nuclear DNA ratio through the cell cycle were followed with quantitative real-time PCR and flow cytometry. During starvation, the cultures initially showed a rapid growth and a 3.5-fold increase of number of cells ml^–1, while at the same time, plastid DNA cell^–1 showed a 3.5-fold decrease, and a 3.6-fold decrease in phycoerythrin fluorescence cell^–1. The decrease in plastid DNA cell^–1 d^–1 closely followed culture growth rate (Pearson correlation, r = 0.91), indicating that existing plastids were diluted within the growing population and that no new plastids were synthesised by the cells. When starved cells were re-fed by the ciliate M. rubra on Days 43 to 51 of the experiment, plastid DNA cell^–1 increased 7-fold up to 14000 16S DNA copies per cell, thereby directly revealing the kleptoplastic behaviour. The implication is that not only availability of the prey M. rubra itself, but also the supply of suitable kleptoplastids might be an important controlling factor for Dinophysis spp. bloom formation and decline.

KEY WORDS: Dinophysis · Myrionecta rubra · Kleptoplastid · Real-time PCR