Comparative study of the ventricular morphology in Otophysi: an evolutionary approach

Abstract

The fish heart is composed of six anatomical components arranged in series. Among them, the ventricle stands out for presenting considerable morphological variations between the species related to the external anatomy, organization of the myocardium and distribution of coronary vessels. One of the forms of classification considers it's myoarchitecture and the level of vascularization, allowing to group it into four main types (I-IV). Although this classification is a tool that, at some level, allows inferences about the evolution of ventricular morphology in fish, no analysis using comparative phylogenetic methods has been performed to date. Still, little is known about cardiac morphology and evolution in neotropical freshwater teleosts. Given the above, the objective of this study will be to bring advances in the understanding of ventricular morphology and evolution in freshwater teleosts of the Otophysi lineage. For description and survey of morphological characters, ventricles of 22 species belonging to four orders (Characiformes, Siluriformes, Gymnotiformes, and Cypriniformes) will be submitted to anatomical, histological and ultrastructural studies. Then, a phylogeny of these species will be proposed based on molecular traits (ultraconserved DNA elements) previously sequenced. Finally, the morphological characters will be incorporated into the resulting phylogeny and analyzed by comparative phylogenetic methods to infer the evolution of ventricular morphology. (AU)