THE UNIQUE HEMOGLOBIN SYSTEM OF PLEURAGRAMMA-ANTARCTICUM, AN ANTARCTIC MIGRATORY TELEOST - STRUCTURE AND FUNCTION OF THE 3 COMPONENTS

Pleuragramma antarcticum (suborder Notothenioidei, family Nototheniida e) is the most abundant fish in the antarctic shelf. This pelagic spec ies has a circum-antarctiac distribution and is characterized by spawn ing migration. This species displays the highest multiplicity of major hemoglobins (three); the other notothenioids have a single one (excep t one species, having two) with relatively low oxygen affinity regulat ed by pH and organophosphates, The hemoglobins of P. antarcticum displ ay strong Bohr and Root effects; however, they reveal important functi onal differences in subunit cooperativity and organophosphate regulati on and, above all, in the response of oxygenation to temperature, De s pite the substitution Val beta E11 --> Ile found in Hb 2, which decrea ses the affinity in human mutants, the hemoglobins have similar oxygen affinity, higher than that of the other notothenioids. Hb 1 has the a lpha chain in common with Hb 2 and the beta in common with Hb 3. The a mino acid sequence of all four chains has been established, Thus the h ematological features of P. antarcticum differ remarkably from those o f antarctic notothenioids, This unique and sophisticated oxygen transp ort system may adequately meet the requirements of the unusual mode of life of this fish.