A circannual rhythm in cysts formation and growth rates in the dinoflagellate Scripsiella trochoidea Stein

The percentages of formed cysts and growth rates were monthly estimated and analyzed rhythmometrically by cosinor for 5 clonal cultures of Scripsiella trochoidea Stein grown for 2 years under laboratory conditions, rended as constant as possible from the view point of environmental temperature (24 +/- 1 degree C), lighting (25 microEin m-2 s-1), and artificial seawater. A circannual rhythm is macroscopically apparent and microscopically (by cosinor) validated for 3 of 5 clones. The data of the other 2 clones did not allow rhythm detecting by the method used, suggesting differences in spectral structure of S. trochoidea strains both in terms of cyst formation and growth rate rhythms.