Thus, during the transition from ectothermic to endothermic life styles, the ancestors of mammals and of birds may have experienced weak genome-wide positive selection to increase the thermostability of their proteins. Conclusion Protein homologs operating at different temperatures have different amino acid composition, both in prokaryotes and in vertebrates. Do eukaryotes show similar effects of thermal adaptation? A small shift of amino acid usage in the expected direction is observed in endothermic ('warm-blooded' mammals and chicken compared to ectothermic ('cold-blooded' vertebrates with lower body temperatures this shift is not simply explained by nucleotide usage biases. Does this observation reflect a causal relationship, or could the apparent trend be caused by phylogenetic relatedness among sampled organisms living at different temperatures? And do proteins from endothermic and exothermic vertebrates show similar differences? Results We find that the observed correlations between the frequencies of individual amino acids and prokaryotic habitat temperature are strongly influenced by evolutionary relatedness between the species analysed however, a proteome-wide bias towards increased thermostability remains after controlling for phylogeny. In particular, protein surfaces in species thriving at higher temperatures appear to be enriched in amino acids that stabilize protein structure and depleted in amino acids that decrease thermostability. Thus, in the case of ectothermic vertebrates, changes in environmental temperature will likely impact the foraging ecology of divers.Īmino acid composition in endothermic vertebrates is biased in the same direction as in thermophilic prokaryotesįull Text Available Abstract Background Among bacteria and archaea, amino acid usage is correlated with habitat temperatures. Analyses of the body mass and temperature dependence of dive duration in 181 species of endothermic vertebrates and 29 species of ectothermic vertebrates show that dive duration increases as a power law with body mass, and decreases exponentially with increasing temperature. Here we show that dive duration in both endotherms and ectotherms largely support the oxygen store/usage hypothesis after accounting for the well-established effects of temperature on oxygen consumption rates. The body mass-dependence of dive duration among endothermic vertebrates is largely supportive of this model, but previous analyses of ectothermic vertebrates show no such body mass-dependence. Common metabolic constraints on dive duration in endothermic and ectothermic vertebratesĭirectory of Open Access Journals (Sweden)įull Text Available Dive duration in air-breathing vertebrates is thought to be constrained by the volume of oxygen stored in the body and the rate at which it is consumed (i.e., “oxygen store/usage hypothesisâ€.
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