1973/06/30 by H. A. v. Stosch · 9 citations
Biochemistry, Genetics and Molecular Biology · Earth and Planetary Sciences · Environmental Science · #Protist diversity and phylogeny #Marine and coastal ecosystems #Microbial Community Ecology and Physiology #Biology #Homothallism #Botany #Zoospore #Gymnodinium #Meiosis #Sexual reproduction #Heterothallic #Dinoflagellate #Sporogenesis #Spore #Ecology #Mating type
paper · pdf · doi:10.1080/00071617300650141
openalex publication_date 1973/06/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
In unialgal culture, Gymnodinium pseudopalustre Schiller (G.p.) and Woloszynskia apiculata sp. nov. (W.a.) multiply respectively by binary fission in the motile state and by motionless zoosporangia, releasing 2, 4 or 8 zoospores. Both species are isogamous, but G.p. is homothallic, W.a. heterothallic. Fusion of the planogametes leads to long-lived planozygotes, which retain two posterior flagella and, while enlarging, assume specific morphologies. The motile stage of the zygotes is terminated by formation of hypnozygotes (resting spores), globular and spiny in G.p., grossly fusiform (‘horned’) and tubercled in W.a. The composition of the hypnozygote walls is described. After their dormancy has been broken by a cold treatment of several weeks in the dark, hypnozygotes of both species germinate when brought back to higher temperature and light. In so doing, those of G.p. excyst one posteriorly biflagellate swarmer as a meiocyte, which, after a stage of nuclear cyclosis or, in karyological terms, zygotene through postzygotene, undergoes two steps of binary fission in the motile stage, separated by several days. In W.a., cyclosis as well as the first meiotic cell division occur inside the closed wall of the hypnozygote (now a meiocyte); thereafter either two swarmers escape and undergo the second meiotic division in a separate zoosporangium or, alternatively, second meiotic nuclear and cell divisions also take place inside the spore wall and four swarmers are finally excysted. Some aspects of dinoflagellate life cycles and taxonomic questions are discussed.