BIOLOGICAL ASPECTS OF RESTING EGG FORMATION, DIAPAUSE AND HATCHING OF SMALL SPECIES ROTIFERS AND ITS APPLICATION TO MASS PRESERVATION TECHNOLOGY

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Mechanism of resting egg formationAmong collected twenty rotifer strains, eight strains had sexual reproductive ability. These exhibited the percent mixis at more than 30% under 30℃ and 16 ppt salinity. Resting egg formation was vigorous with Hawaii and Langkawi strains. The HPLC analysis clarified that gamma-aminobutyric acid and 5- HT are present in rotifers, suggesting that these may function as neurotransmitters in rotifers. We conducted several assays using the polyclonal antibody of male mate recognition pheromone obtained from Koshiki strain. The antibody binded well with strains except Hamana and Spanish strains. Male mate recognition to females among strains were equally inhibited when females were bound with the antibody. These suggest that the contamination of other small-species rotifer strains will not reduce the male mate recognition in the population.Mass production and preservation of resting eggsUsing Hawaii and Hamana strains, we conducted mass production of resting eggs under optimal condition obtained above. Semicontinuous culture method was used to enhance the mixis induction for a longer period of time. For Hawaii strain, the resting egg harvest in three tanks were 7, 5 and 1.1 (million ) resting eggs per 500 liter tank, and it was 65, 79 and 27 million resting eggs for Hamana strain. Resting eggs were mass preserved at 4oC after lyophilization, and we obtained 50-60% hatching.