Cardiac morpho-dynamics in Rana esculenta: influence of sex and season

Morpho-dynamic aspects of the frog (Rana esculenta) heart were correlated to seasonal and sexual traits. The statistical analysis of the data (696 frog specimens: 448 males and 248 females), collected during 8 years of routine research on frog cardiac physiology, indicated that cardiac biology is characterised by sexual dimorphism. The relative cardiac weight of males was higher than that of females of similar size. With respect to the males of similar size, female frogs revealed an increased relative ventricular weight and ventricular contractile capacity. The morphometric analysis showed that the ventricular growth was achieved through significant myocardial enlargement accompanied by a reduction of the lacunary spaces. This is more pronounced in females during the breeding period. The correlation between sexual maturity and ventricular morpho-functional changes revealed that in male frogs sexual maturity correlates with a remarkable increment of the ventricular weight associated with higher values of pulse pressure. This data indicate that sex and season-related factors influence cardiac morpho-dynamics in R. esculenta.