Nutritional quality of prey (Brachionus calyciflorus) affects the population growth of predatory rotifers (Asplanchna sieboldi) (Rotifera)

Abstract

The nutritional quality of prey rotifer Brachionus calyciflorus grown on two types and three combinations of food was tested using the predatory species Asplachna sieboldi. B. calyciflorus was grown using Chlorella vulagaris, diluted and pH-adjusted waste water from tortilla industry (agua de nejayote) and their mixture. The smallest sized adults (6.24 X10 um3) were observed in B. calyciflorus populations grown in nejayote water while the largest individuals (7.98 X10 um3) were obtained from those fed on algae. The body size of brachionids raised on the mixture of alga and nejayote water showed intermediate results. Population growth curves of A. siedoldi grown on different prey combinations (algae vs nejayote water and their mixture) and densities (2.5-20 prey/ml/24 hr) showed oscillations in predators abundance. In general, an increase in the abundance of prey resulted in higher densities of prey populations, regardless of prey nutritional status. However, there was a significantly higher abundance of Asplanchna fed on prey grown in agua de nejayote as compared to those fed on either only algae plus agua de nejayote. A consistently higher population growth in A. sieboldi fed on B. calyciflorus raised on nejayote water implied better nutritional quality of prey rotifers, despite their smaller body size. The population growth rate (r) increased significantly with increasing prey availability regardless of the diet on which the prey was cultured. The highest population growth rate recorder in the study was 0.95+-0.01 and th lowest was 0.33+-0.04 for A. sieboldi fed on B. calyciflorus grown on nejayote water and nejayote water plus algae, respectively. When A. sieboldi individuals were maintained (in the absence of prey brachionids) in algae, algae+nejayote water or nejayote water alone, no reproduction ocurred, although the asplanchnids continued to live for a few more days in medium with nejayote water with or without addition of algae.