Dynamics of a Rotifer Brachionus rotundiformis, fed on 5 species of marine phytoplankton

초록

Rotifer Brachionus rotundiformis were reared in laboratory from egg to death offering 5 species of marine phytpplankton as food to investigate the egg production rate, fecundity, and mortality. The offered phytoplankton was Skeletonema, Isochrysis galbana, Thalasiosira weissflogii, Tetraselmis suecica, Chlorella ellipsoidea, and mixed diet of them. Number of eggs carried by individuals was also investigated. The life span varied from 15 to 20 days : the shortest for individuals fed on I. galbana and the longest for T. suecica. The first egg production occurred between 12-24 hours, and was not differed greatly with food species. Daily mortality was also similar varying between 2.5-3.6%. Egg production rate and fecundity showed a two-fold variation : the highest was for mixed phytoplankton diet, followed by C. elliposidea, T. suecica, Th. weissflogii, I. galbana, and S. costatum. Two- or three-egg production was also the highest for the mixed phytoplankton diet. Fecundity varied in time and showed two or three peaks : the first peak was in general higher than the second or third one, except for C. elliposidea. The results clearly indicated superiority of mixed phytoplankton diet for rotifer B. rotundiformis over the single phytoplankton species.