AI Insight
This study challenges the widely accepted theory that larger cells have lower metabolic rates due to reduced surface area-to-volume ratios. Researchers examined nine salamander species with varying cell sizes and found no relationship between cell size and cellular respiration rates, Na+/K+-ATPase pump costs, or mitochondrial respiration in liver and heart tissue. These results contradict theoretical predictions and align with organismal-level studies that also fail to show correlations between cell size and metabolic rate.
Why it matters
This finding questions fundamental assumptions used in models of life history evolution and metabolic scaling across species. It suggests that factors other than cell size may be more important in determining tissue-level metabolic rates, potentially requiring revision of theoretical frameworks in evolutionary physiology and comparative biology.
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Evolutionary diversity in metabolic rate underlies differences in physiology, morphology, and life history across the tree of life. Cell size has been proposed as an important determinant of metabolic rate. The mechanisms underlying this proposed connection are based on the lower surface area to volume ratios in larger cells. As relative surface area decreases, the cost of maintaining ion gradients across the cell membrane through action of the Na+/K+-ATPase pump are posited to decrease, lowering overall metabolic costs. Despite strong theoretical support for this model, and its incorporation into broader models of life history evolution, empirical measurement of Na+/K+-ATPase activity in species that differ in cell size has been lacking. Here, we study nine species of salamanders of the genus Plethodon that span a large range of cell sizes approaching the animal upper limit. We compare basal cellular respiration rates, relative cost of the Na+/K+-ATPase pump, and maximal mitochondrial respiration rates in liver and heart tissue. Contrary to predictions, we find no support for a relationship between cell size and any of these mitochondrial respiratory variables. We reconcile this surprising result with broader phylogenetic studies showing a lack of correlation between cell size and metabolic rate at the organismal level.