WHAT CAN WE LEARN FROM DAPHNIA FILTERING SCREENS

The relative filtering setae length (RFSL; the length of filtering set ae on the third pair of thoracic limbs expressed as a per cent of cara pace length) was determined in three developmental categories of a res ervoir population of Daphnia galeata and its relationship to phytoplan kton fluctuation. RFSL of adult females immediately after moulting ref lects the current food conditions in the reservoir (higher RFSL at low er food level, and vice versa), whereas RFSL of adult females close to moulting reflects the food conditions several days or weeks ago. RFSL of juvenile animals reacts the most quickly to changing food conditio ns, provided the temperature allows frequent moulting. Higher RFSL can also indicate poor-quality food for daphnids, in situations when food quantitative parameters (such as chlorophyll a) show high values.