The endogenous biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFAs) in fish is species specific and depends on several factors, such as trophic level, feeding habits, environmental characteristics, taxonomic position and mainly the conservation and activity of fatty acid desaturases (Fads) and elongases (Elovl). Therefore, the study of the evolutionary conservation of these genes in different species of fish has become routine in order to understand lipid metabolism and its essentiality in each species studied. Despite its importance to fish, there is a lack of understanding how the environment and trophic level affect the capacity for biosynthesis of LC-PUFAs in freshwater carnivorous teleosts. The red piranha (Pygocentrus nattereri) is a carnivorous freshwater fish of interest in Brazilian aquaculture. In this present project, at a bioinformatics level, we identified the genes and characterized the proteins of the Fads2 and Elovls present in the red piranha genome. Sequence comparison and phylogenetic analysis suggested that the Fads2 and Elovls proteins are closely related to previously characterized proteins from freshwater carnivorous and herbivorous fish species. As a conclusion, we suggest that the red piranha has the possible, at least partial, ability to bioconvert C18 PUFA into LC-PUFAs through the activities of Fads2 and Elovls.