

North Sea, 14/1/2014. Gyrodinium spirale and Coscinodiscus radiatus (middle spec. is dividing).
The nucleus of this dinoflagellate bulges out of the cell. In a single frame at 100%, the stringy mass of chromosomes can clearly be seen, as is typical for a dinokaryon:

Olympus inverted, 20x/0.7 objective. The dinokaryon is 25x15um.
Best wishes, René