The toxic dinoflagellate Cochlodinium polykrikoides (Dinophyceae) produces resting cysts

► We present visual confirmation of the production of resting cysts by Cochlodinium polykrikoides in laboratory cultures. ► We document sexually mating cell pairs, planozygotes, temporary cysts, resting cysts, and cyst germination. ► Resting cyst germination occurred up to one month after cyst formation and 2-40% of resting cysts were germinated. ► Cyst production may account for the recurrence of annual C. polykrikoides blooms as well as the global expansion of blooms.