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Interactive effects of hypoxia and dissolved nutrients on the physiology and biochemistry of the freshwater crayfish, Paranephrops zealandicus
A key contributing factor to the decline of the “at risk” freshwater crayfish, Parnephrops zealandicus, is the presence of hypoxia associated with eutrophication. However, there is little information regarding the impacts that dissolved nutrients have on the physiological and biochemical mechanisms that this, and other, freshwater crayfish employ to cope with lowered dissolved oxygen. Using semi-closed box respirometry, crayfish were exposed to an abrupt hypoxia (1.3 kPa) in the absence or presence of either ammonia (30 mg L-1 total ammonia; 0.04 mg L-1 as unionised ammonia) or nitrite (20 mg L-1), over a 6-h exposure. Respiratory (oxygen consumption; haemolymph oxygen partial pressure), cardiac (heart rate), and biochemical (haemolymph acid-base status, glucose and lactate; tissue glucose and lactate) end-points were measured. In hypoxia alone, haemolymph oxygen partial pressure, glucose and pH fell, while haemolymph lactate increased. The only significant effects of nutrients on hypoxic responses were a further decline in haemolymph oxygen partial pressure, and an enhanced hypoglycaemia in the presence of nitrite. These effects may be linked to a nitrite-mediated improvement in tissue perfusion. Overall these data indicate little additional impact of the presence of nutrients on the responses of P. zealandicus to hypoxia.
MF17262 Accepted 18 December 2017
© CSIRO 2017