Since many stages of development are conserved across vertebrates, this information has generated considerable insight into congenital heart defects in humans. Genetic screens in zebrafish have revealed genes and pathways underlying development in the heart. The morphological differences created during chamber development are guided by changes in gene expression patterns, a process well conserved in vertebrates, regardless of whether there are one or two atria or ventricles. The focus on fish heart developmental patterns has primarily been due to the use of zebrafish as a model organism of vertebrate development. Gene expression programs specific to each chamber are likely regulating key aspects of chamber formation. Key morphogenetic events during heart ontogenesis are conserved across vertebrates. ![]() In mammals, 23% of cardiac-specific genes show differences in expression between the atria and the ventricle. This research will be reviewed in the context of roles of the atrium and ventricle in fish in achieving variability in myocardial contractility. Between these sources much has been revealed about the contractile properties of the two chambers. Research has tended to focus on inotropic or chronotropic responses of the heart to stress such as temperature in larger fish such as trout, or on development through the use of zebrafish mutants. The vertebrate-specific development of multiple chambers with enough muscle to generate higher systemic pressures allowed for perfusion of larger and more complex tissues.įish show great variability in the development of the heart and modification of heart performance capacities to meet tissue perfusion demands imposed by differences in life history. The heart is the first definitive organ to develop and become functional, as embryological survival depends on its proper function. ![]() Fish heart design is reflective of the needs for oxygen delivery to working skeletal muscle in an often oxygen poor environment. ![]() These chambers develop from a simple linear tube and differ not only morphologically but also physiologically with different characteristic rates of contractility. The two chambers acting as pumps are the atrium and ventricle, a simplified version of that seen in tetrapods. The heart of teleosts is unique in structure, composed of four chambers in series: venous sinus, atrium, ventricle and bulbus arteriosus. Across vertebrates, the fish heart is structurally relatively simple.
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