REES, B.B*; SUDRADJAT, F.A.; LOVE, J.W.: Acclimation to hypoxia increases survival time of zebrafish during lethal hypoxia

Survivorship of zebrafish, Danio rerio, was measured during lethal hypoxic stress after pre-treatment in water at either ambient oxygen or at a lowered, but non-lethal, level of oxygen. Acclimation to non-lethal hypoxia (ca. 10% air-saturation) for 48 h significantly extended survival time during more severe hypoxia (ca. 5% air-saturation) compared to survival of individuals with no prior hypoxic exposure. The magnitude of the acclimation effect depended upon the sex of the fish; hypoxia pre-treatment increased the survival times of males by a factor of approximately 9, and that of females by a factor of 3, relative to controls. In addition, survival time of control and hypoxia acclimated fish depended upon when in the year experiments were conducted. Survival times were 2 to 3 times longer when measured in the late fall or winter compared to survival times measured during the spring or summer. These results demonstrate a direct survival benefit of short-term acclimation to hypoxia in this genetically-tractable fish. The fact that the acclimation effect depended upon the sex of the fish and the season during which experiments were conducted demonstrates that other genetic and/or environmental factors affect hypoxia tolerance in this species. This work was supported by National Science Foundation grant IBN 9723050 (to BBR) and by a student internship from the Freeport-McMoRAN Foundation (to FS).