Growth, trichome size and akinete production of Cylindrospermopsis raciborskii (cyanobacteria) under different temperatures: Comparison of two strains isolated from the same pond

Summary Coiled morphotype C ylindrospermopsis raciborskii ( W oloszynska) S eenayya et S ubba R aju that forms a water bloom in a shallow pond in northern T aiwan exhibits a negative correlation between trichome size and temperature. To investigate how temperature influences the growth and trichome size of C . raciborskii , two C . raciborskii strains isolated from the pond in A ugust and F ebruary were grown at three temperatures (18, 24 and 30°C). Both strains exhibited the lowest and highest specific growth rates at 18°C and 24°C, respectively, and the trichomes became the largest at 18°C. However, specific growth rates of the strain isolated in A ugust exceeded those of the strain isolated in F ebruary, and the trichomes of the strain isolated in F ebruary were larger than those of the strain isolated in A ugust regardless of temperature. Moreover, although both strains produced larger numbers of akinetes at higher temperatures, the strain isolated in A ugust produced many more akinetes than did the other. These findings suggest that the two strains are not identical, leading to the conclusion that the C . raciborskii population in the pond consists of at least two ecotypes. Large trichome formation and akinete production are thought to be different types of countermeasure against cold of C . raciborskii , and the patterns of investment in developing these functions seemed to vary between the strains.