Morphological development of resting cysts in cultures of the marine dinoflagellate Lingulodinium polyedrum (= L. Machaerophorum)

Abstract The previously undescribed morphological development of resting cysts of the living marine dinoflagellate Lingulodinium ("Gonyaulax") polyedrum has been observed in laboratory cultures. Referred to as L. machaerophorum in cyst‐based taxonomy, this species has a fossil record extending back at least to the Early Eocene. In our cultures, planozygotes preparing to encyst showed a distinctive interstice in the peripheral cytoplasm and often displayed a characteristic swimming behavior. The transition from motile planozygote to morphologically mature hypnozygote (resting cyst) took approximately 10–20 minutes. Encystment began with several events occurring simultaneously: (1) the cell stopped swimming and came to rest at the bottom of the observation chamber, (2) flagella were expelled from their respective thecal grooves, (3) localized swelling of a membrane external to the theca formed bubble‐like protrusions on the surface of the cell, (4) the theca began to dissociate along one or more plate sutur...