Different constraints shaped red blood cell characteristics in vertebrates

Area of Science:

• Comparative physiology
• Vertebrate hematology
• Evolutionary biology

Background:

• The relationship between body mass and hematological parameters is well-studied in mammals, but less so in other vertebrates.
• Red blood cells (RBCs) are crucial for oxygen delivery, suggesting a link between hematology and metabolic rates.
• Previous research has not comprehensively explored these correlations across diverse vertebrate groups.

Purpose of the Study:

• To investigate correlations between body mass, metabolic rates, and hematological parameters in a wide range of vertebrate species.
• To identify specific hematological parameters that exhibit significant relationships with metabolic demands and body size.
• To explore the influence of factors like endothermy/ectothermy and genome size on these correlations.

Main Methods:

• Analysis of hematological data from 513 vertebrate species.
• Statistical correlation analysis between body mass, metabolic rates, and various hematological parameters.
• Comparison of hematological parameters between endothermic and ectothermic species.
• Investigation of the relationship between RBC volume (MCV) and genome size in species with nucleated RBCs.

Main Results:

• Most hematological parameters showed weak, though significant, correlations with body mass or metabolic rates.
• Hematocrit levels were significantly higher in endotherms than in ectotherms.
• Mean corpuscular volume (MCV) demonstrated a correlation with metabolic rates and hemoglobin-oxygen affinity.
• In non-mammalian vertebrates with nucleated RBCs, MCV was strongly correlated with genome size.

Conclusions:

• Hematological parameters have coevolved with metabolic demands across vertebrate species.
• Genome size acts as an extrinsic constraint influencing RBC characteristics, particularly in non-mammals.
• MCV is a key hematological parameter linked to metabolic rate and evolutionary factors beyond gas exchange.