The heart of a flying mammal

Abstract

The ability of true flight and the great diversity of the order Chiroptera might raise questions about the morphology and functionality of the bats’ heart. Here we aimed to describe anatomical aspects of the heart of the great fruit-eating bat, Artibeus lituratus (Phyllostomidae, Stenodermatinae) and its functional features. Twenty-five individuals had their hearts dissected and described. We found that the A. lituratus heart shares general characteristics of the mammalian and Chiropteran heart, such as the bilateral anterior vena cava, the bulky pulmonary conus, the developed venae cavae sinus, the valve in the posterior vena cava and the papillary muscles attached to the right ventricle septal wall. Some features seem species-specific, like the anomalous membranous structures found in the right ventricle of some individuals, never seen before in other mammals, and also the presence of the Thebesian valve. Some of the features found might be related to flight adaptations as a highly developed set of pericardial ligaments. This complex set of ligaments has never been described before for another mammal, which probably acts by keeping the heart in position while the bat rests upside down. The pericardial ligaments have infiltrations of white fat, which, together with the deposits present on the surface of the heart, possibly act as energy reserves for the heart muscle. In this work, we suggest the presence of two anterior venae cavae has the function of optimizing the blood flow that returns to the heart.