OXIDATIVE STRESS IN SEA BASS DICENTRARCHUS LABRAX LARVAE: INTERACTION OF HIGH DIETARY DHA CONTENTS AND SEVERAL ANTIOXIDANT NUTRIENTS

摘要

It is widely known that marine fish larvae have a huge requirement for n-3 long-chain polyunsaturated fatty acids (LC-PUFA) to reach a good culture performance. Among n-3 LC-PUFA, docosahexaenoic acid (DHA) seems to be more essential than other PUF Asand that is why it is included in high amounts in enrichment media. The objective this work was to study the effect of high dietary contents of DHA on sea bass (Dicentrarchus labrax) larvae in combination with different antioxidant nutrients, such as vitamin E (vitE), selenium (Se), or vitamin C (vitC). In a first study, three graded levels of DHA (1, 3 and 5%) were tested together with two levels of vitE (150 and 300 mg.lOOg"1), paying attention to larval culture performance and to muscle morphology.The presence of muscular lesions, described as hyaline degeneration, was increased along with the DHA content. Nevertheless, vitE increase from 150 to 300mg.l00g"' helped to reduce the incidence of these lesions and enhanced larval survival and growth when a 3% of DHA was included in the diets. In the light of these results, a new experiment was planned, including a new diet, containing the highest content of DHA and vitE (5/300). However, histopathological evaluation proved that when a level of 5% of DHA was employed, the increase in vitE from 150 to 300mg did not prevent the appearance of muscular lesions. In addition, the oxidative status was altered, as indicated by TBARS content, in larvae fed with a high content of DHA, especially if compared tothose fed a 1 % of DHA, indicating that the oxidation of DHA and vitE was the cause of the muscular lesions. On the other hand, in the same work, more detailed features of the muscular lesions were shown through the thick and ultra-thin sections, provingthat they show similarities with mammals muscle dystrophy. Semi-thin sections revealed focal lesions consisting of degenerated fibres with hypercontracted myofilaments and extensive sarcoplasm vacuolization affecting both red and white muscle. Ultra-thin sections of degenerating muscle fibres showed diffuse dilatation of sarcoplasmic reticulum, disorganized myofilaments, and autophagic vacuoles containing myelin figures and dense bodies.