Hemoglobin concentration in normal diploid and intersex triploid chickens: genetic inactivation or canalization?

Of 19 adult intersex chickens examined, 17 were triploid animals with ZZW sex chromosomes. Triploid erythrocytes were about 1.5 times the size of diploid erythrocytes, and were present in amounts that were about two-thirds the number of diploid erythrocytes. Both diploid and triploid animals had similar hematocrits and hemoglobin concentrations. Triploidy is reflected in a relative increase in RNA, as well as in DNA, per erythrocyte. This, in addition to the trisomic mode of inheritance observed in several genetically distinct loci determining isoantigens, indicates that all three sets of chromosomes in the triploid animals are genetically active. Apparently, there is a homeostatic mechanism maintaining the concentration of hemoglobin for the species in spite of triploidy and its effect on erythrocyte size.