The heart of Sparus auratus: a reappraisal of cardiac functional morphology in teleosts

This morphodynamic study provides an insight on how the architecture of the heart ventricle of the gilthead seabream (Sparus auratus) is designed to accomplish the functional performance typical of an active teleost species. Using an in vitro working heart preparation, mechanical performance was analyzed under loading (i.e., preload and afterload) challenges. The hearts were very sensitive to filling pressure increases. Maximum cardiac output (CO: 55.66 +/- 4.54ml/min/kg body weight; mean +/- SEM) and maximum stroke volume (VS: 0.42 +/- 0.027 ml/kg body weight; mean +/- SEM) were obtained at an input pressure of 1 kPa. When exposed to output pressure (OP) changes, the hearts maintained constant CO and SV up to about 4 kPa; further increases of afterload significantly compromised mechanical performance. Surprisingly, this "athletic" pumping performance was achieved by an entirely trabeculated pyramidal ventricle. The ventricular architecture was characterized by a system of small luminae and trabecular sheets radiating outward from the central lumen. The most peripheral part of the ventricular chamber contained single trabeculae and the corresponding lacunary spaces. The ventricular cavity was bounded by an outer myocardial monolayer "shell" to which the peripheral trabeculae were attached. Myofibril organization differed in the trabeculae and in the outer monolayer. The structural features challenge common beliefs regarding the typical "athletic" teleost heart design.