Effects of plant oligosaccharides derived from dragon fruit on growth,reproduction and survival of freshwater crustacean Daphnia magna

The freshwater crustacean Daphnia is widely used as live food for ornamental fish. To increase production, food supplementations are required when culturing Daphnia. Here, we aimed to clarify the effects of plant oligosaccharides derived from dragon fruit (DFO) on growth rate, egg production, number of first clutch juveniles and survival of Daphnia supplemented with five different concentrations of DFO, that is 0, 1, 3, 9, 27 mg/L. The results showed the growth and reproduction of Daphnia were enhanced when supplemented with DFO. Growth rate of Daphnia supplemented with 9 mg/L DFO was the highest among all treatments. The time that Daphnia produced the first clutch eggs was shorter in high concentration of DFO (3, 9, 27 mg/L). The number of juveniles in the first clutch increased in treatments of higher concentration of DFO (3, 9, 27 mg/L). These results suggest that plant oligosaccharides derived from dragon fruit increase growth and fecundity of Daphnia. Survival rates of Daphnia were 100% except for the treatment supplemented with 27 mg/L of DFO in which the survival rate was reduced to 87%. To our knowledge, this is the first functional evidence demonstrating that oligosaccharides derived from dragon fruit enhance growth and fecundity of Daphnia.