Long-Chain Polyunsaturated Fatty Acids n−3 (n−3 LC-PUFA) as Phospholipids or Triglycerides Influence on Epinephelus marginatus Juvenile Fatty Acid Profile and Liver Morphophysiology

SIMPLE SUMMARY: Fish feeding is responsible for almost 60% of the total cost of marine fish production, so nutritional studies are always in demand. Dusky grouper is a promising species for aquaculture, but studies of the species’ nutrition are still lacking. The present study investigated the effects of fatty acids, provided as different lipid classes in four different diets, for Epinephelus marginatus fingerlings and evaluated their physiological and morphological responses in order to provide new insights about grouper nutrition. The fatty acids, provided as different lipid classes, modified the physiological and morphological responses of E. marginatus, showing that the inclusion of these lipids as different classes should be considered in order to obtain better results in terms of fish fillet quality. These results provided valuable insights into the nutrition and physiology of dusky groupers, helping to pave the way for the establishment of this fish species as a produced species worldwide. ABSTRACT: Phospholipids (PL) are membrane components composed of fatty acids (FA), while triglycerides (TG) are a main source of energy and essential FA. Polyunsaturated FA (PUFA), such as docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA), are essential for marine carnivorous fish; thus, an 8-week experiment was performed to evaluate the influence of DHA and EPA, provided as PL and TG, on the morphophysiology of Epinephelus marginatus juveniles. A basal diet was manufactured, and DHA and EPA in PL form (PL1—low amount PL2—high amount) and TG form (TG1—low amount; TG2—high amount) were added. Dusky grouper juveniles were equally distributed in 12 tanks of 20 animals each, and liver and muscle were sampled for metabolic analysis. The total hepatic lipids in PL1 and PL2 were higher when compared to the initial, TG1 and TG2 groups. Total lipids in muscle were higher in PL2 and TG1 than PL1 and TG2, respectively. Diets rich in DHA and EPA in PL and TG resulted in higher deposition of these FA in the muscle polar fraction. However, fish fed diets containing lower amounts of DHA and EPA in PL and TG stored those in the muscle neutral fraction and liver, centralizing the storage of DHA and EPA.