Uptake of latex beads as size-model for food of planktonic rotifers

Selection of particles ingested by planktonic rotifers was investigated using different-sized fluorescent latex beads (ca 0.05–10 μm diameter). Keratella cochlearis, Keratella quadrata, and Polyarthra dolichoptera preferred 1–2-μm diameter beads, whereas Synchaeta pectinata selected for 2–3-μm particles. However, the size-frequency distribution of beads ingested indicated great variability. The 'incipient limiting level' of particle concentration (ILL) for rotifers tested with 2-μm beads was high. Keratella cochlearis had the lowest ILL with 5×105 beads ml-1 and Synchaeta pectinata the highest with 1×10 6 beads ml-1. The clearance rate (CR) varied for all species between 0.1 and 0.4 μl ind.-1 h-1. Keratella cochlearis had the highest CR with 0.4 μl ind.-1 h-1 at food concentration of 5×105 beads ml-1. S. pectinata and P. dolichoptera had their maximum CR with 0.34 and 0.20 μl ind.-1 h-1, respectively, at 7.5×105 beads ml-1.