Meeting Abstract
Hypoxia is currently an increasingly pervasive occurrence in aquatic ecosystems. As oxygen is required on a biochemical level for the survival of most animals, hypoxia can have negative effects on an animal’s performance by limiting its capacity for aerobic metabolic activity. This stressor is compounded by increasing water temperatures, which decrease oxygen solubility in water and increase the aerobic metabolic rate of ectothermic organisms. Under hypoxia, some animals adjust their behavior and physiology to limit their oxygen consumption and maximize the amount of oxygen they extract from the environment. However, hypoxia exposure can also limit a fish’s tolerance to higher temperatures (measured as critical thermal maximum, CTmax). Here, we explored the relationship between thermal tolerance and hypoxia exposure on a widespread African Cichlid, Pseudocrenilabrus multicolor. We reared F1 offspring of parental stock collected from Uganda in a full factorial split brood design with two treatments (hypoxia and normoxia), and measured their CTmax under their rearing treatment and the alternative. This allowed us to compare of the effects of short-term versus lifelong exposure to hypoxia on thermal tolerance in these fish. Our results provide further evidence of the negative effects of hypoxia on a fish’s thermal tolerance under acute exposure; fish raised in normoxia had significantly lower CTmax values under hypoxic test conditions. Interestingly, the CTmax values of the fish raised in hypoxia were not significantly affected by test condition, indicating that lifelong exposure to hypoxia likely results in long-lasting developmental changes that better equip the fish for life under hypoxia, but that lower their ability to handle thermal stress.
