The cyst-theca relationship of Bitectatodinium tepikiense (Dinophyceae)

Bitectatodinium tepikiense Wilson cysts, first described from Pleistocene s ediments and generally associated with sediments in temperate to cold-tempe rate waters, were germinated to establish cultures. The motile thecate cell s derived were referable to Gonyaulax digitale (Pouchet) Kofoid. For the fi rst time detailed morphological information is given for the motile stage o f this cyst-theca relationship. Cultures were re-encysted; the cultured cys ts showed a range of morphology from spherical cysts to those with an apica l boss. The taxonomy of Gonyaulax digitale and cyst-theca relationships wit hin the Spiniferites plexus are discussed but, given the debate surrounding the status of the genera Gonyaulax and Spiniferites, no formal taxonomic r eassignments are proposed. These observations confirm that establishing cul tures of cyst taxa in problematic dinoflagellate groupings and meticulous h igh-resolution scanning electron microscopic observation of the specimens h ave great potential for elucidating cyst-theca relationships and clarifying dinoflagellate taxonomy.