other پژوهشي Orginal research papers As the main organ of the cardiovascular system, the vertebrate heart has been the focus of a myriad of morphological, functional, and molecular studies. The heart of fishes has not escaped from this stream of interest, and a wealth of information has accumulated on this subject over the past 50 years (Icardo, 2012). The heart of sturgeons is related to that of other ancient fish and the elasmobranches in that it has a long conus arteriosus endowed with a muscular coat and several rows of conus valves (Icardo<em> et al</em>., 2002). The subepicardium is a thin layer rich in collagen and elastin, fibroblasts, vessels, and nerves (Icardo <em>et al.,</em> 2000). Although this constitutes a general description, the subepicardium of the bulbus can be a more complex layer. For instance, it may contain lymphocytes, plasma cells, and dendrite-like cells, and has been implied to be involved in the development of the humoral immune response (Icardo <em>et al.</em>, 1999). This is surprising, but it is not an isolated feature in fish. The subepicardium of the sturgeon contains thymus-like tissue (Icardo <em>et al</em>., 2002) which has been implicated in the establishment and the maintenance of the cellular immune responses. Cavernous hemangioma, Epicardium, Sturgeon, Acipenser baerii 835 839 http://jifro.ir/browse.php?a_code=A-10-2992-5&slc_lang=other&sid=1 A. Rezaie a.rezaie@scu.ac.ir 100319475328460029645 100319475328460029645 Yes Faculty of veterinary medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran. Faculty of veterinary medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran. M. Alishahi 100319475328460029646 100319475328460029646 No Faculty of veterinary medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran. Faculty of veterinary medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran. Z. Tulaby Dezfuly 100319475328460029647 100319475328460029647 No Faculty of veterinary medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran. Faculty of veterinary medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.