AME 45:163-170 (2006)  -  doi:10.3354/ame045163

ABSTRACT: The grazing and growth rates of the algivorous heterotrophic flagellate (HF) Diphylleia rotans were investigated on toxic (Microcystis aeruginosa NIER-10001, M. aeruginosa NIES-298, M. viridis NIES-102 and M. wesenbergii NIES-104) and non-toxic (M. aeruginosa NIES-101) Microcystis strains as well as other different algae such as the green alga Chlorella^TM (Aquanet), and diatoms Cyclotella meneghiniana and Stephanodiscus hantzschii. The flagellate D. rotans showed active growth when fed M. aeruginosa and lower levels of growth when fed Chlorella^TM, but no growth when fed C. meneghiniana and S. hantzschii. The flagellate grew actively at 25°C and at a pH range between 6 and 9. The highest maximum specific growth rate (1.88 d^–1) and a high ingestion rate (27.0 prey HF^–1 d^–1) by D. rotans were observed when they were fed the most toxic of the 5 Microcystis strains, M. aeruginosa NIER-10001. These results suggest that D. rotans has a high tolerance to M. aeruginosa and may undergo microcystin-mediated growth.

KEY WORDS: Algivores · Heterotrophic flagellates · Diphylleia rotans · Microcystis spp. · Microcystin-mediated growth · Ingestion