Hemoglobin Levels and Red Cell Ionic Composition in Goldfish (Carassius auratus) Exposed to Constant and Diurnally Cycling Temperatures

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Abstract
Hematological response in goldfish (Carassius auratus) held at constant temperature (20, 25, 30 °C) was compared with that of animals exposed to a diurnal temperature cycle (25 ± 5 °C), with particular reference to overall oxygen carrying capacity and cellular electrolytes influencing haemoglobin–oxygen affinity. All groups were sampled at 03:00, 09:00, 15:00, and 21:00. Hemoglobin and hematocrit were determined, as were plasma and packed red cell levels of water, sodium, potassium, magnesium, calcium, and chloride. The latter were used to estimate mean cellular ion concentrations. Temperature treatment influenced response. Under constant temperature conditions hemoglobin levels tended to increase at higher temperatures. This was associated with compositional changes which would be expected to reduce affinity and facilitate oxygen release. By contrast, under cycling temperature conditions hemoglobin levels were elevated whereas erythrocytic electrolyte concentrations tended to be stable. Observations are discussed in terms of their bearing on the interpretation of studies on the acclimatory process.Key words: goldfish, Carassius auratus; blood chemistry, temperature, hemoglobin, O2-carrying capacity