E. crenulata produces three morphologically distinct spore types, two of which (female and male) conjugate to form a uninucleate zygote. The zygote undergoes successive division to produce four daughter cells of unequal size, but that resemble the non-mating spore type (the neutral spores). Coats et al. 2011.
More detailed: Male spores remained active for several hours, swimming erratically between short periods of quiescence, but never formed pairs suggestive of conjugation. A day or two after formation, male spores lost motility and degenerated. Female and neuter spores persisted for 2--3 days before degrading. Addition of fresh neuter spores to wells containing active male spores elicited no response. By contrast, addition of female spores generated an immediate reaction, with male spores forming a cloud of rapidly swimming cells around each spherical female spore. Only one male spore attached to the surface of each female, with the surrounding cloud of spores almost immediately dispersing. Prior to attachment, male spores developed a small protuberance or copulation globule on their ventral surface near the insertion of the flagella. Thus, conjugation occurred with the ventral surface and flagellar basal bodies of the male spore pressed against the female spore. The flagella of attached males remained active, causing the conjugating pairs to rotate rapidly. Motility soon ceased, as resorption of the male flagella accompanied fusion of the paired cells. Karyogamy preceded completion of cytogamy. Conjugation lasted 20-30 min, with the zygote remaining inactive for ~2 h before undergoing two successive divisions presumably representing meiosis. Daughter cells of the first division were of equal size and sometimes showed a spindle with metaphase arrangement of chromosomes as the second division proceeded. The second division was not equal, with the resulting chain of four cells having two small central cells flanked by larger individuals. The chain of post-meiotic daughter cells gradually dissociated, giving rise to small egg-shaped cells (7--11 µm by 5--8 µm in vivo) that resembled neuter spores. When 24 female spores were transferred to wells containing male spores, all were fertilized and underwent meiosis. The remaining population of female spores (44 total) retained in the absence of male spores failed to divide. Neuter spores did not divide whether maintained alone or incubated in the presence of male spores.

E. crenulata and E. cachoni each produce three types of spores: motile dinokont spores, non-motile spherical spores, and non-motile egg-shaped and spindle-shaped spores, respectively (Coats 1988; Coats et al. 1994). Coats (1988) suggested that the spindle-shaped spores of E. cachoni might be cysts, as they persisted in the lab for several days. By contrast, the egg-shapes spores of E. crenulata degenerated in 2-3 days when held at near ambient water temperature and are therefore not likely resting cysts.

Generation: <1 month
Reproduction_mode: sexual
Reproduction_mode: asexual
Symbiont: horizontal