Stress response in two Antarctic teleosts (Notothenia coriiceps Richardson andChaenocephalus aceratus Lönnberg) following capture and surgery

Abstract

Blood chemistry and haematological parameters have been determined in two Antarctic teleosts,Notothenia coriiceps Richardson andChaenocephalus aceratus Lönnberg, held at around 1°C.Notothenia coriiceps has a low haemoglobin content compared to tem-perate-zone species, whereasC. aceratus apparently lacks respiratory pigments. Blood samples were obtained by cardiac puncture following landing or using chronically implanted post-branchial arterial cannulae. Although both species showed a similar acidosis on capture (arterial pH as low as 7.5 versus the final recovery value of around 7.9),C. aceratus took 48 h to reestablish baseline values whileN. coriiceps recovered within 12 h, despite initially showing a greater degree of hypercapnic hypoxia. Surgery led to a more severe disturbance of acid-base regulation inN. coriiceps thanC. aceratus (arterial pH of 7.5 versus 7.8) but needed only half as long for recovery. A progressive decrease in arterial oxygen tension and increase in arterial carbon dioxide tension (both more pronounced inN. coriiceps) with level of acidosis was observed down to arteria pH 7.2 InC. aceratus this was accompanied by a rise in blood lactate (up to 10 mmol·1^-1 in some individuals), whileN. coriiceps showed only a modest and transient lactacidosis. Stress inN. coriiceps therefore induces primarily a respiratory, rather than a metabolic acidosis, whereas inC. aceratus both components are present. A differential response to stress is also indicated by an elevated, though low noradrenaline titre inN. coriiceps following surgery and capture, whileC. aceratus was little affected by surgery. However, both species show an unusually weak catecholamine response to induced stress.