Cardiac morphology of Phalacrocorax brasilianus.

Phalacrocorax brasilianus is an aquatic bird that is widely distributed in Neotropical territories. This study sought to describe, characterize and compare the heart of this species, analyzing its morphology. Seven preserved adult specimens were donated to the Laboratory of Animal Histology and Embryology at the Federal Rural University of the Amazon (UFRA). The birds were subsequently reused at the Laboratory of Animal Morphological Research at UFRA. The specimens underwent a series of procedures including thawing, folding of the skin and musculature and removal of the sternum, part of the ribs and lungs, to access the heart within the coelomic cavity. Macroscopic analyses were performed, which involved the application of neoprene latex to identify the arteries and veins present in the organ and in the bodies of the animals. The specimens were then fixed with a 10% aqueous formaldehyde solution, followed by photodocumentation, both in situ and ex situ, and 3D scanning. Additionally, three stains were performed in the microscopic analyses, these being Hematoxylin and Eosin, Gomori Trichrome and Orcein, and scanning electron microscopy. Thus, specific characteristics were described in the cardiovascular system of P. brasilianus. These include the left atrioventricular valve containing two cusps attached to the chordae tendineae, while the right atrioventricular valve consists only of a thin layer in a single muscular projection and lacks chordae tendineae. It was concluded that the heart of the cormorant has hyaline-type cartilage that is a component of the cardiac skeleton, present at the base of the aortic valve.