Abstract
Life cycles of several species belonging to the marine generaDissodinium Klebs in Pascher andPyrocystis Murray ex Haeckel are described. The two known species ofDissodinium, D. pseudolunula Swift ex Elbr. & Dreb., (=D. lunula auct. nonnull.) andD. pseudocalani (Gonnert) Drebes ex Elb. & Dreb. are ectoparasites of copepod eggs. In this genus, sporogenesis, with obligate sequence from primary cyst to secondary cyst to dinospores, occurs by palintomy.Dissodinium is placed into the order Blastodiniales Schiller and its position in this order is discussed. The asexual life cycle ofPyrocystis spp. represents an alternation between a dominating coccoid stage and a morphologically different transitory reproductive stage. The reproductive bodies may be either athecate aplanospores, athecate uni- or biflagellate planospores or thecate biflagellate planospores. Thecal morphology of thecate planospores resembles those ofGonyaulax Diesing. The occurrence of both, athecate aplanospores and thecate planospores in the same species, is discussed.Pyrocystis is regarded as belonging to the order Pyrocystales Apstein. The possible derivation from the Gonyaulacaceae Lindemann is suggested. In addition, the generaDissodinium andPyrocystis are redefined. A description ofD. pseudolunula as well as a list of synonyms and references for detailed descriptions ofP. lunula (Schutt) Schutt, not includingD. pseudolunula, is given.
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