Respiratory adaptation and energy metabolism in Antarctic nototheniid fishes

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Abstract
Haemoglobin concentration and haematocrit vary considerably between four species of nototheniid fishes from Antarctica, and may be related to differences in metabolic demand. Red cell ATP and lactate were measured in the pelagic species Trematomus borchgrevinki and the benthic T. bernacchii at normal (-2.0°C) temperatures and after 7–36 h heat stress at +5°C. Resting fishes have higher ATP: Hb ratios (2.0–2.4 mole/mole) at -2.0°c than do fishes at +5°c (0.9–1.8 mole/mole). These ratios fall during continuous swimming, and the blood lactate level rises. The importance of ATP measurements in the control of haemoglobin oxygen affinity and in relation to the theory of ‘cold adaptation’ is discussed.