Morphological perspectives of the heart of Rhinella marina: Contributions to comparative anatomy and evolutionary biology.

BACKGROUND: Rhinella marina, an anuran with established invasive populations in the Amazon biome, has a tricavitary heart with two atria and a single ventricle. Given its invasive tendencies and the management challenges it poses in certain areas, a detailed morphological study of this species is important for understanding its biology and for comparisons across taxa. METHODS: We examined ten adult individuals using mesoscopic techniques, light microscopy (LM), and scanning electron microscopy (SEM). RESULTS: The heart occupies the midline region of the body, dorsal to the sternum, between the lung lobes, and anterior to the liver. It exhibits two atria entirely divided by an interatrial septum, a ventricle with pronounced trabeculation, and a conus arteriosus containing a spiral valve. The myocardium displayed transverse striations and intercalated discs; the organ is bounded by an endocardium and epicardium and enclosed by a richly vascularized pericardium. CONCLUSIONS: These observations expand knowledge of Rhinella marina's cardiac microstructure, offering data relevant to comparative cardiovascular anatomy, evolutionary interpretation, and functional considerations in amphibian cardiac physiology.