Dissolved oxygen saturation is crucial for gas bladder inflation in turquoise killifish (Nothobranchius furzeri)

Providing optimal conditions for early-life gas bladder inflation of captive fish is one of the biggest challenges in fish culture. It also applies to laboratory fishes. Turquoise killifish (Nothobranchius furzeri Jubb, 1971) is a popular research model in biogerontology due to its short lifespan. Annual killifish in laboratory culture frequently suffer from an inability to inflate their gas bladder which may stem from suboptimal environmental conditions in captivity. Here, we investigate (1) the effect of dissolved oxygen (DO) saturation and (2) access to the water surface on gas bladder inflation and hatching success of turquoise killifish. We further histologically examine the gas bladder development from its primordial form to full inflation. In accordance with physoclistous nature of turquoise killifish, access to the water surface is not necessary for gas bladder inflation. We found that hatching success was highest in the treatment with constant or decreasing DO saturation. In contrast, the highest proportion of larvae with inflated gas bladders was found in the treatment with DO oversaturated water (130%) which was induced by the addition of an oxygen tablet. Larvae inflated their gas bladders within 2 to 48 h post-hatching. These findings represent a major step toward a solution to a persistent problem in laboratory culture of this increasingly important model organism.