Oxygen limitation and tissue metabolic potential of the African fish Barbus neumayeri: roles of native habitat and acclimatization

Abstract

BackgroundOxygen availability in aquatic habitats is a major environmental factor influencing the ecology, behaviour, and physiology of fishes. This study evaluates the contribution of source population and hypoxic acclimatization of the African fish, Barbus neumayeri, in determining growth and tissue metabolic enzyme activities. Individuals were collected from two sites differing dramatically in concentration of dissolved oxygen (DO), Rwembaita Swamp (annual average DO 1.35 mgO2 L-1) and Inlet Stream West (annual average DO 5.58 mgO2 L-1) in Kibale National Park, Uganda, and reciprocally transplanted using a cage experiment in the field, allowing us to maintain individuals under natural conditions of oxygen, food availability, and flow. Fish were maintained under these conditions for four weeks and sampled for growth rate and the activities of phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS), and cytochrome c oxidase (CCO) in four tissues, liver, heart, brain, and skeletal muscle.ResultsAcclimatization to the low DO site resulted in lower growth rates, lower activities of the aerobic enzyme CCO in heart, and higher activities of the glycolytic enzyme PFK in heart and skeletal muscle. The activity of LDH in liver tissue was correlated with site of origin, being higher in fish collected from a hypoxic habitat, regardless of acclimatization treatment.ConclusionsOur results suggest that the influence of site of origin and hypoxic acclimatization in determining enzyme activity differs among enzymes and tissues, but both factors contribute to higher glycolytic capacity and lower aerobic capacity in B. neumayeri under naturally-occurring conditions of oxygen limitation.

Effect of temperature on hypoxia tolerance and its underlying biochemical mechanism in two juvenile cyprinids exhibiting distinct hypoxia sensitivities

“…Environmental hypoxia is a common abiotic challenge caused by temperature fluctuations, low photosynthetic activity and low or stagnant water flow that many aquatic organisms experience in their habitat (Karim et al, 2003;Diaz and Breitburg, 2009;Martínez et al, 2011). At any sufficiently low level of dissolved oxygen would negatively impact the behavior and/or physiology of fish.…”

“…These changes are associated with the mobilization, transportation and utilization of substrates (primarily glycogen and glucose from liver and muscle) and the transportation and clearance of metabolites (primarily lactate) (Mandic et al, 2013). However, the extent and location of the metabolites used depend on the duration and severity of hypoxia, as well as the pathway, tissue and species involved (Martínez et al, 2011). Crucian carp is considered as the champion of hypoxia tolerance (Nilsson and Renshaw, 2004;Dhillon et al, 2013).…”

Interspecies variation in hypoxia tolerance, swimming performance and plasticity in cyprinids that prefer different habitats

“…Oxygen availability in aquatic habitats is a major environmental factor that influences the ecology, behaviour and physiology of fish (Martínez et al, 2011). Hypoxia [defined as any level of dissolved oxygen (DO) low enough to negatively impact the behaviour and/or physiology of an organism] occurs naturally in many aquatic systems (Pollock et al, 2007).…”

Metabolic and molecular responses in Nile tilapia,Oreochromis niloticusduring short and prolonged hypoxia

“…This hypoxia can affect growth, food consumption, and the physiological state of fishes by impairing energy metabolism in fish tissues (Foss et al 2002). Hypoxia can moreover lead to high rates of mortality of fish in aquatic systems depending upon their degree of hypoxia tolerance (Martínez et al 2011).…”