Increased Growth of Chlorella pyrenoidosa (Chlorophyta) in Response to Substances from the Rotifer Brachionus calyciflorus

ABSTRACT

We assessed the response of Chlorella pyrenoidosa to substance(s) from the rotifer Brachionus calyciforus using flow cytometry and PHYTO-PAM fluorometry. The cell density of C. pyrenoidosa in the rotifer water treatment was significantly higher than that in the control, suggesting that substance(s) from the rotifer stimulated the alga to grow faster. Additionally, the cell size of C. pyrenoidosa in the rotifer water treatment was consistently smaller than that in the control. Esterase activity and chlorophyll fluorescence of C. pyrenoidosa cells in the rotifer water treatment increased and were higher than those in the control but were not significantly different. The maximal efficiency of PSII (Fv/Fm) and the effective quantum yield of PSII (Φ_PSII) of C. pyrenoidosa in the rotifer water were also consistently higher than those in the control, although these differences also were not significant. The pattern, however, does seem to support the idea that C. pyrenoidosa responded to infochemical produced by the rotifer.