Effects of cyanobacterium exopolysaccharides on life-history of Ceriodaphnia cornuta SARS

Abstract

The objective of the present investigation was to verify if Anabaena spiroides exopolysaccharides sustains growth and reproduction of Ceriodaphnia cornuta. The animals were raised in controlled laboratory conditions and fed exclusively on A. spiroides exopolysaccharides, which were obtained from filtered stationary growth phase A. spiroides cultures. A molecular weight cut-off of 12-14 kDa was used to separate the exopolysaccharides from low molecular weight materials. The lyophilized exopolysaccharides were dissolved in filtered and autoclaved reservoir water at a concentration of 15 mgL -1 (0.22 ± 0.01 mg C animal -1 day -1 ). These results were compared with animals fed on seston at natural concentration obtained by filtering (68 μm) Barra Bonica Reservoir water (0.23 ± 0.01 mg C animal -1 day -1 ). Several life history parameters (duration of embryonic development, generation time, reproductive performance, age-specific length, primipara age and length) were obtained during 15-day experiments. Growth rate (GR) and weight-specific secondary production were also quantified. Exopolysaccharide-fed organisms had better growth and reproductive performance (0.091± 0.004 GR; 51 ± 4.59 eggs produced per female) than seston-fed individuals (0.078 ± 0.010 GR; 30.90 ± 7.25 eggs produced per female). These results show that such macromolecules are a potential food source, fulfilling nutritional requirements to sustain growth and reproduction of C. cornuta and supports trophic relationships in aquatic ecosystems.