Morphometry and resting egg production potential of the tropical ultra-minute rotifer Brachionus rotundiformis (Manado strain) fed different algae

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The ultra-minute marine Brachionus strains have been found in some mangrove estuaries and brackish water ponds located in Manado, North Sulawesi, Indonesia. These are classified as Brachionus rotundiformis. The algal species influenced the degree of morphological plasticity in size. Lorica length of egg bearing wild rotifer (mean ± SD = 150.7 ± 17.6μm) was much smaller than that fed Tetraselmis (199.2 ± 10.6μm), but similar to those fed Nannochloropsis (150.7 ± 12.9μm) and Isochrysis (151.5 ± 14.9μm).　The mixis induction, which is the potential of resting egg production was further examined for clone culture. Percentage of mictic females and males in batch cultured rotifers fed Tetraselmis was higher than those cultures fed Isochrysis. In individual cultures, about 70 % of the hatched amictic eggs of rotifers fed Isochrysis became mictic females, and 87 % when rotifers were fed Tetraselmis. The life span of the mictic females fed Isochrysis was much longer than that fed Tetraselmis. The number of unfertilized mictic eggs produced by a female during her lifetime were 15.3 and 16.4 for rotifers fed Isochrysis and Tetraselmis, respectively. Life span and post-reproductive life was longer when rotifers were fed Isochrysis, but shorter when fed Tetraselmis. The tested rotifer strain has a high potential for the mass production of resting eggs. It can be performed more efficiently by the use of Tetraselmis diet.