2024 Volume 38 Issue 2 Pages 65-72
Vertebrate heart evolution has undergone substantial morphological and functional adaptations in response to diverse environments. Our previous study comparing ventricular stiffness in anurans from different habitats suggested that terrestrial anurans possess stiffer ventricles than aquatic counterparts. However, as this hypothesis was tested on only one species per habitat, the generality of this trend remained uncertain. This study aimed to expand upon these findings by examining two representative species: aquatic Xenopus borealis (X. bor) and terrestrial Buergeria buergeri (B. bue). Pressure loading tests were conducted to measure ventricular stiffness, while histological analyses examined structural differences. Pressure-loading tests revealed that the ventricles of B. bue were significantly stiffer than those of aquatic X. bor, which was consistent with previous findings. Histological analysis revealed that the increased stiffness correlated with a thick and compact myocardium layer and elevated collagen content in terrestrial species. These findings indicate that the ventricles of anurans stiffen during terrestrial adaptation, providing insights into the evolutionary changes in heart structure and mechanical properties in response to environmental shifts.
