Do the hemoglobinless icefishes have globin genes?

Among piscine taxa, the Antarctic icefishes (family Channichthyidae) prosper in the absence of erythrocytes and hemoglobin, a unique condition among adult vertebrates. The genomes of three icefish species and four red-blooded notothenioid species were probed using α- and β-globin cDNA from the red-blooded Antarctic fish Notothenia coriiceps. High-stringency hybridization signals with the α-globin probe, but none with the β-globin probe, on genomic DNAs of both hemoglobinless and red-blooded fishes suggest that icefishes retain remnants of α-globin genes in their genomes but have lost the gene that encodes for β-globin, either through deletion or through rapid mutation. Northern blot analysis of major hematopoietic and non-hematopoietic tissues shows that the α-globin-related sequences of icefishes are nonexpressed derivatives of the α-globin genes of their red-blooded relatives. Mechanisms leading to the hemoglobinless phenotype are discussed in relation with the expression of myoglobin in the Channichthyidae family.