The pigment composition of Dinophysis norvegica Ehrenberg from the central Baltic Sea differs from the normal pigment pattern found in dinoflagellates, which contain peridinin as a typical marker pigment. In D. norvegica isolated by cell fractionation of field samples, the major carotenoid was alloxanthin, a typical cryptomonad pigment. No evidence was found that the presence of alloxanthin was due to a recent phagotrophic uptake of cryptomonads, so the presence of alloxanthin in D. norvegica may be a consistent feature of a permanent endosymbiosis.