Diagnosis_Genus: Dissodinium Klebs in Pascher, emend. Elbr. & Dreb. 1978. Marine ectoparasitic dinophytes, host: crustacean eggs. Asexual reproduction (sporogenesis) by obligate sequence of primary cysts, secondary cysts, and formation of planospores (dinospores). Primary cyst spherical, with large food vacuole. Nucleus spherical, located in the parietal cytoplasm. Chromatophores present or lacking. Inside the primary cyst wall the protoplast divides by repeated binary fission (palintomy) into 2, 4, 8, 16, or more secondary cysts. The secondary cysts form 5 to 16 or more (rarely less than 5) dinospores. Dinospores small, Gymnodinium- or Gyrodinium-shaped, biflagellate, athecate. The dinospores attach to the host, loose their motility and form a sucker organelle. Hypertrophic growth by phagotrophic uptake of host material. Finally, the growth phase terminates with formation of a primary cyst. No bioluminescence.
Diagnosis_Species: Dissodinium pseudolunula Swift ex Elbr. & Dreb. 1978. Ectoparasite of copepod eggs. Sporogenesis by two successive cyst stages terminating with formation of dinospores. Primary cyst spherical, 60-100-
130 µm in diameter. Cytoplasm parietal, surrounding a large vacuole filled with nutritional material. Nucleus spherical, lying in a peripheral cytoplasmic aggregation. A few greenish yellow chromatophores present, multiplying during sporogenesis. The primary cyst divides to form 8 or 16 (rarely 2 or 4) lunate secondary cysts which are liberated from the decaying primary cyst wall. The secondary cysts, about 100-140 µm from tip to tip across, contain a large nutritional vacuole. The secondary cysts form usually 5-8 (range 2-16) dinospores. Dinospores measuring 23-28 µm in length, 18-21 µm in width, athecate, biflagellate, of the Gymnodinium type, greenish yellow pigmented by numerous chromatophores, containing chl a. In each secondary cyst one dinospore contains the residue of the large vacuole as a red globule. After release from the secondary cysts the dinospores may either infest a new host or may become non-motile with following encystment. Distribution: marine plankton. When the host is absent, the species survives with a distinctive pair of twin resting cysts (previously described as Pyrocystis margalefii). The twin resting cysts are formed inside a lunate secondary sporangium, after duplication (Gomez 2013). Each infected egg may provide 32 new infective dinospores for the following spring.
Body_trophonts_length: 60-140 µm
Body_spores_length: 23-28 µm
Body_spores_wide: 18-21 µm
Body_cysts_length: 100-131 µm (Drebes 1981)
Sequence_SSU: FJ473378, FJ473379