Dwarf and giant geckos from the cellular perspective: the bigger the animal, the bigger its erythrocytes?

Abstract

Summary Although evolutionary and ecological consequences of body size changes are relatively well understood, the proximate mechanisms of body size alteration at a cellular level are often surprisingly neglected, especially in vertebrates. The question of whether larger animals are made from larger cells is rarely tested in an explicit phylogenetic framework, i.e. among closely related species with known phylogeny. Here we explore the relationship between erythrocyte and body size in a small gecko family (Eublepharidae) exhibiting large body size variation. We found positive interspecific correlation of cell and body size. Assuming that size of other cell types changed in a similar way to red blood cell size, we can conclude than c. 15–20% of body size change in this group could be attributed to cell size variation. As larger cells are generally more frugal than smaller cells, we hypothesise that a macro‐evolutionary trade‐off exists between body complexity and energetic efficiency. We believe that knowing how particular animal lineages have solved this trade‐off during body size evolution will help us explain much of the variation in ecophysiological traits among clades as well as within them.