Brachionus plicatilis (rotifer), a type of zooplankton, is widely used in aquaculture as a live food for newborn larvae such as bluefin tuna.However, the conventional rotifer has a problem that it is small in size and is not suitable for larvae that have grown to some extent.

 The RIKEN Nishina Center Biological Irradiation Team has developed a technology to induce gene mutations by irradiating biological samples with heavy ion beams.This time, a joint research group of RIKEN, Fisheries Research and Education Agency, and Nagasaki University has announced that the Notojima strain (maximum size 320 μm), which is the largest of the current Japanese worm strains, is irradiated with a heavy ion beam to induce mutations. We aimed to create a large worm.

 At RIKEN RI Beam Factory, rotifers of Notojima strain were irradiated with carbon (C) ion and argon (Ar) ion beams under multiple dose conditions, and large individuals were selected and cultured repeatedly.As a result, 340 large mutant lines of 370 to 56 μm, which can be said to be “megawamushi”, could be selected, and 3 of them had a higher growth rate than the original strain (Notojima strain).These can be expected to be put into practical use as new useful feeds.

 In addition, as a result of investigating the frequency of appearance of mutant strains in order to search for conditions suitable for large-scale mutagenesis, the optimum irradiation conditions were 200 Gy (gray) for C ion irradiation and 50 Gy for Ar ion irradiation.This study revealed that the heavy ion beam breeding technology can also be applied to zooplankton, which has opened the way for further enlargement and improvement of other prey organisms.

 Fish species such as yellowtail and queer, which have a larval survival rate of 1 to 5% in the aquaculture business, will grow if they are not given sufficient food of the appropriate size for the size of the larvae. It will be late, and hunger may cause co-eating.If the survival rate of larvae is improved by introducing the large rotifer line produced in this study, it is expected to contribute to the improvement of aquaculture production.

Paper information:[Bioscience, Biotechnology, and Biochemistry] Application of heavy-ion-beam irradiation to breeding large rotifer

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