An ecophysiological interpretation of hemoglobin multiplicity in three herbivorous marine teleost species from New Zealand

Hemoglobin components (isohemoglobins) and their isoelectric points (pI) were analysed for three herbivorous marine teleosts, and the functional properties of their unfractionated, stripped hemolysates were determined. Kyphosus sydneyanus and Girella tricuspidata possess six isohemoglobins and share a dominant cathodic band (pI = 8.61). Odax pullus possesses four isohemoglobins characterised by two strongly anodic bands (pI = 5.80, 4.89). Equilibrium binding studies of the hemolysate complexes from K. sydneyanus and G. tricuspidata revealed high oxygen affinities which were relatively insensitive to pH, whereas oxygen affinity was markedly lower and more pH sensitive in O. pullus. Moreover, hemoglobin-oxygen affinity was less temperature-sensitive in K. sydneyanus than in O. pullus. These observations support the hypothesis that hemoglobin oxygen loading in the cool-temperate species (O. pullus) may be compromised in the most northerly (warm) limits of its distribution, and that ecologically equivalent species in warmer and thermally variable habitats (K. sydneyanus and G. tricuspidata) possess more cathodic isohemoglobins which are less influenced by pH and temperature. (C) 1998 Elsevier Science Inc. All rights reserved.