Syndiniales

The Syndiniales are an order of dinoflagellates, found exclusively as endosymbionts of the tintinnid ciliates, crustaceans, fish, protozoa, algae, and other dinoflagellates. The trophic form is often multinucleate, and ultimately divides to form motile spores, which have two flagella in typical dinoflagellate arrangement. They lack a theca and chloroplasts, and unlike all other orders, the nucleus is never a dinokaryon. A well-studied example is Amoebophrya, which is a parasite of other dinoflagellates and may play a part in ending red tides.