Investigation of a rotifer (Brachionus calyciflorus) - green alga (Scenedesmus pectinatus) interaction under non- and nutrient-limited conditions

Two-day life cycle tests with the rotifer Brachiomus calyciflorus were run to study the nutritional quality effects to rotifers of Scenedesmus pectinatus grown under non-limiting nitrogen limiting and phosphorus limiting conditions and the feedback of the rotifers oil the Food algae. Under nutrient-limited conditions of its algal food Brachionus production was depressed, animals produced fewer eggs and were smaller sized. Clearance rates of Brachionus offered non-nutrient-limited and nutrient-limited Food were similar. The number of cells per colony was similar for S. pectinatus Under nitrogen limited and phosphorus limited conditions both in the absence and presence of Brochionus. Cell volumes phosphorus limited S. pectinatus were larger than those of nitrogen limited cells. The most dramatic response of the food alga S. pectinatus was observed in non-nutrient-limited conditions: a strong, size enlargement occurred only in file presence of Brachionus. This was caused by a higher share of eight-celled colonies and larger individual Cell volumes in the Presence of rotifers than in their absence. S. pectinatus might gain an advantage of becoming larger in moving out of the feeding window of its enemy, but nutrient limited conditions might undermine the effectiveness of such reaction.