title: The anatomical components of the cardiac outflow tract of the gray bichir, Polypterus senegalus: their evolutionary significance.
abstract: It has been reported that in chondrichthyans the cardiac outflow tract is composed of the myocardial conus arteriosus, while in most teleosteans it consists of the nonmyocardial bulbus arteriosus. Classical studies already indicated that a conus and a bulbus coexist in several ancient actinopterygian and teleost groups. Recent work has shown that a cardiac outflow tract consisting of a conus and a bulbus is common to both cartilaginous and bony fishes. Nonetheless and despite their position at the base of the actinopterygian phylogenetic lineage, the anatomical arrangement of the cardiac outflow tract of the Polypteriformes remained uncertain. The present study of hearts from gray bichirs was intended to fill this gap. The cardiac outflow tract of the bichir consists of two main components, namely a very long conus arteriosus, furnished with valves, and a short, intrapericardial, arterial-like bulbus arteriosus, which differs from the ventral aorta because it is covered by epicardium, shows a slightly different spatial arrangement of the histological elements and is crossed by coronary arteries. Histomorphologically, the outflow tract consists of three longitudinal regions, distal, middle and proximal, an arrangement which has been suggested to be common to all vertebrates. The distal region corresponds to the bulbus, while the conus comprises the middle and proximal regions. The present findings reinforce the notion that the bulbus arteriosus of fish has played an essential role in vertebrate heart evolution as it is the precursor of the intrapericardial trunks of the aorta and pulmonary artery of birds and mammals.
authors.affiliation: Department of Animal Biology, Faculty of Science, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain. Electronic address: acduran@uma.es.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Durán
authors.affiliation: Department of Animal Biology, Faculty of Science, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain.
authors.forename: Ismael
authors.initials: I
authors.lastname: Reyes-Moya
authors.affiliation: Department of Animal Biology, Faculty of Science, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain.
authors.forename: Borja
authors.initials: B
authors.lastname: Fernández
authors.affiliation: Department of Animal Biology, Faculty of Science, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Rodríguez
authors.affiliation: Department of Animal Biology, Faculty of Science, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain.
authors.forename: Valentín
authors.initials: V
authors.lastname: Sans-Coma
authors.affiliation: Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, 600 Highland Avenue, Madison, WI 53705, USA.
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Grimes
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003331:Coronary Vessels / Q000033:anatomy & histology* / Q000166:cytology; D005399:Fishes / Q000033:anatomy & histology* / Q000145:classification*
keywords: Bulbus arteriosus; Conus arteriosus; Heart evolution; Heart morphology; Polypterus