Anatomical and histological characterization of the heart of the scarlet ibis ( Eudocimus ruber )

Detailed information on the cardiac morphology of the scarlet ibis (Eudocimus ruber) remains limited. This study aimed to characterize the gross and microscopic anatomy of this species' heart and provide morphometric data. We examined six specimens (three males and three females) using gross anatomical analysis, morphometry, conventional radiography, three-dimensional scanning, light microscopy, and scanning electron microscopy. The mean heart mass was 5.93 ± 1.49 g (n = 6), corresponding to 1.10 ± 0.23% of body mass, and the mean radiographic cardiothoracic ratio was 66.90 ± 5.78% (n = 3). Macroscopic examination identified three venae cavae: the right and left cranial venae cavae and the caudal vena cava. The left atrioventricular valve had two cusps with chordae tendineae and papillary muscles, whereas the right atrioventricular valve had a single muscular fold. Histological examination identified uninucleated and binucleated Purkinje fibers in the subendocardial region, extending into myocardial muscle bundles. The base of the aorta showed hyaline cartilage containing chondrocytes and chondroblasts, with no bone tissue identified in the examined sections. These findings provide anatomical, morphometric, and histological data on the heart of E. ruber and a basis for future comparative studies of avian cardiac morphology.