Further observations on cultures of the marine ciliated protozoan Uronema marinum Dujardin

Abstract

The rate of cell division of a Robin Hood's Bay strain of Uronema marinum Dujardin was determined at various combinations of salinity and temperature after ≈ 2 years in laboratory culture. Comparison with a previous experiment showed that there had been minor changes in the response surface. A strain of U. marinum isolated from the Tees Estuary had a markedly different response to the two factors and reproduced most rapidly at 25%. S and 17.5 C, compared with 35 %. S and 25 C for the Robin Hood's Bay strain. In tolerance experiments the Robin Hood's Bay strain survived at salinities of 8.8–55%., temperatures of 0–34 C, and at pH values of 6.5–9.5. The ciliates survived when the dissolved oxygen level was < 1 mg l −1, but died when hydrogen sulphide was introduced into the cultures.