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Journal of Experimental Biology 141,97-111 (1989)
Published by Company of Biologists 1989

Hypoxic Responses in a Fish From a Stable Environment: Blood Oxygen Transport in the Antarctic Fish Pagothenia Borchgrevinki

R. M.G. WELLS ¹, G. C. GRIGG ², L. A. BEARD ², and G. SUMMERS ³

¹ Department of Zoology, University of Auckland, Auckland, New Zealand
² School of Biological Sciences, The University of Sydney, Australia
³ Fish Processing Section, Division of Horticulture and Processing, DSIR, Auckland, New Zealand

The effects of hypoxic exposure on whole-blood oxygen-affinity were examined in the antarctic fish Pagothenia borchgrevinki. Fish exposed to P_OO2 = 60 mmHg for 11-14 days at -1.5°C had a P₅₀ value of 20.6±4.8mmHg (S.D., N=13) at pH8.16, compared with 31.1 ±4.3mmHg (N=10) at pH8.00 for normoxic fish. Exposure to low oxygen levels resulted in a significant (66 %) rise in haemoglobin concentration, and erythrocyte [ATP] decreased by approximately 27%. There was no evidence for erythrocyte swelling. An aberrant gill morphology was observed in six fish and these showed unexpectedly high erythrocyte ATP levels. Oxygen-carrying capacity increased by approximately 40% in hypoxic fish and was correlated with a 34 % decrease in spleen mass. Despite the fact that antarctic fish have exceptionally low demands for oxygen and are unlikely ever to encounterenvironmental hypoxia, this antarctic fish has the necessary machinery to respondto hypoxia in a way that is typical of teleosts that naturally inhabit oxylabile environments. The ability to make short-term adaptive changes in the O₂ delivery system in response to hypoxic exposure may be typical for vertebrates in general, rather than a feature seen only in those organisms which encounter environmental hypoxia on a regular basis.

Key words: antarctic fish, hypoxia, blood, ATP

Accepted on May 16, 1988