Rotifer

Rotifers are microscopic freshwater filter-feeding zooplankton (100-350 micrometers). They use a crown of cilia (the corona) to create water currents that sweep suspended particles (1-20 micrometers) into the mouth. They are non-selective ciliary filter feeders, similar to Daphnia in feeding mode but targeting smaller particles and with higher weight-specific metabolic rates due to their smaller body size (allometric scaling). Rotifers reproduce primarily through parthenogenesis with very short generation times (1-3 days), enabling rapid population responses to food availability. Their primary food is planktonic algae, with secondary feeding on periphyton, bacteria, nanoflagellates, surface algae, and suspended detritus. They cannot eat settled detritus. Rotifers have higher mass-specific ingestion (about 1.7 times body carbon per day) and respiration rates than crustacean zooplankton due to smaller body size. They are strictly freshwater organisms (optimal 0.5 PSU, lethal above 8 PSU) and prefer warm water (stressed below 8 or above 30 degrees Celsius). Rotifers have minimal energy reserves -- unlike copepods with lipid stores, they crash rapidly without food (starvation mortality up to 10% per day). The model includes two density-dependent mortality mechanisms: self-crowding (similar to Daphnia, up to ~6% per day) and Daphnia mechanical interference (Gilbert 1988) -- large cladocerans suppress rotifers through filtering currents that damage or dislodge rotifers, and through physical displacement from food patches. This interference is not predation but competition, and it scales with Daphnia biomass density (up to ~4% per day at high Daphnia density). Their fecal pellets are very small, with 70% staying suspended. When rotifers die, 50% of their biomass stays suspended. Ecologically, rotifers occupy an intermediate position between the microbial loop and the classical food web, serving as prey for raptorial copepods (copepods) and competing with Daphnia for planktonic food. Large Daphnia populations can competitively exclude rotifers through both food competition and mechanical interference.