Production of albino chub mackerel (Scomber japonicus) by slc45a2 knockout and the use of a positive phototaxis-based larviculture technique to overcome the lethal albino phenotype

• Published in: Aquaculture 2022-11, Vol.560, p.738490, Article 738490
• Main Authors: Kawamura, Wataru, Hasegawa, Niki, Yamauchi, Akihiro, Kimura, Takashi, Yahagi, Hana, Tani, Reoto, Morita, Tetsuro, Yazawa, Ryosuke, Yoshizaki, Goro
• Format: Article
• Language: English
• Subjects: Albino; Chub mackerel; CRISPR/Cas9; Phototactic behavior; Rotifer
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2022.738490

The albino mutation has been used as a visible genetic marker to evaluate offspring resulting from transplanting donor germ cells into recipients to produce donor-derived gametes in surrogates. Using albino mutants as either recipients or donors makes it possible to easily identify the donor-derived offspring based on body color. The chub mackerel (Scomber japonicus) is a promising recipient species for xenogeneic gamete production of commercially valuable scombrids such as bluefin tuna; however, no body-color mutants of this species have been reported. Using the CRISPR/Cas9 system, we produced F1 albino chub mackerel harboring a biallelic null mutation in the solute carrier family 45a2 (slc45a2) gene. However, albino larvae ingested significantly less rotifers than wild-type larvae when reared with a normal feeding density of rotifers, resulting in zero albino larvae survival beyond 12 days post hatch. To overcome this lethality, we developed a novel “spotlight method” of larviculture, in which positive phototaxis is used to attract both rotifers and larvae to create an ultra-high-density feeding area in a larval rearing tank. Under these conditions, albino larvae ingested as much rotifers as wild-type larvae, thus improving albino larvae survival. Finally, we confirmed albino chub mackerel completely lack melanin pigmentation, indicating that we have developed a potentially useful recipient for germ cell transplantation in Scombridae species. •We successfully produced F1 albino chub mackerel by biallelic knockout of the slc45a2 loci.•Albino larvae die because of failure to ingest rotifers.•Using phototaxis (“spotlight method”), rotifers and larvae increase their encounter frequency.•The spotlight method markedly increased survival of albino larvae.•Albino mackerels would be useful recipients carrying a visible marker for germ cell transplantation.