Nucleotypic effects without nuclei: Genome size and erythrocyte size in mammals

Previously reported haploid genome sizes (C-values) and erythrocyte sizes ( measured as mean dry diameters) were compared for 67 species of mammals rep resenting 31 families and 16 orders. Measurements on erythrocytes of four s pecies of bats were also included in the study. Erythrocyte size was signif icantly positively correlated with genome size at each of the specific, gen eric, familial, and ordinal levels, with the relationship becoming much str onger following the exclusion of the order Artiodactyla, a group unique amo ng mammals in terms of red blood cell morphology. Physiologically, these re sults are relevant in light of the known relationship between C-value and m ass-corrected metabolic rate in homeotherms. In evolutionary terms, they pr ovide insights into the constraints on genome expansion among mammals and a re therefore of interest in attempts to solve the long-standing C-value eni gma (also known as the C-value paradox).