Modern Dinoflagellate Cysts and Evolution of the Peridiniales

Abstract

The resting cysts (spores) of over 30 species of modern marine and fresh water dinoflagellates belonging to the genera Gonyaulax, Proteceratium, Peridinium, Diplopsalis, Diplopsalopsis, Diplopeltopsis, and Scrippsiella are described morphologically and their systematic relationships with fossil dinoflagellates and hystrichospheres are discussed. These modern cysts were studied in vivo in North Atlantic phytoplankton at Woods Hole and in a series of over seven hundred single-cell incubation experiments. Fossil or subfossil cysts were also examined from Caribbean, Mediterranean, and western Arabian Sea sediments. It is concluded that modern resting cysts of thecate dinoflagellates are homologous with some fossil dinoflagellates and hystrichospheres and systematic morphological fluctuations follow patterns already known; and relations reflect evolution of the Peridiniales.