Growth dynamics of Olisthodiscus luteus in outdoor tanks with flowing coastal water and in small vessels

Growth rates and periodicity of division of Olisthodiscus luteus were studied in outdoor tanks provided with a continuous flow of coastal water carrying a low density of wild plankters including O. luteus, during summer in 1981–1983. Cells collected from the tanks were individually cultured in small tissue culture chambers in the laboratory to observe growth rates and periodicity of division. A portion of an O. luteus patch on the wall of the tank was also cultured in a 1,000‐m1 volumetric flask hung in the tank. High growth rates, 2.0–5.0 div d−1, were observed in the tank. There was a strong tendency for large cells to dominate in the tank at the beginning of their fast growth phases and to be replaced by small cells toward the end of these growth phases. In small chambers O. luteus attained a growth rate of 3.3 div d−1; growth rates of large cells inoculated into these chambers were much higher than those of small cells. Growth rate in the flask was 2.3 div d−1. Olisthodiscus luteus showed a great preference for dark‐associated cell division. An apparent reciprocal codominance was observed between O. luteus and diatoms in the tank.