Variations in fatty acids composition in different tissues of the European eel (Anguilla anguilla L.) males during induced sexual maturation

Abstract

Summary As no studies have been carried out to investigate the role of fatty acids in male European eel (Anguilla anguilla) maturation, the main aim of this work was to determine which fatty acids could play a central role in sexual maturation. To this end, European eel males were hormonally induced to sexual maturation and variations in fatty acid composition in muscle, liver, testis and milt were studied. Eels were injected weekly with hCG (Human Chorionic Gonadotropin) for 13 weeks and 10 eels per week were sacrificed. Histological analysis was performed to determine the spermatogenic stage of each male. In muscle, no variations or preferential utilization of fatty acids were detected. In liver, MUFAs (Monounsaturated Fatty Acids) were the most abundant fatty acids in the first weeks, while in the last week PUFAs (Polyunsaturated Fatty Acids) showed the highest concentrations. In testes, PUFAs content increased due to DHA (Docosahexaenoic acid), EPA (Eicosapentaenoic acid) and AA (Arachidonic acid) accumulation, while MUFAs diminished especially due to oleic and palmitoleic acid decrease. Linolenic (EPA and DHA precursor) and linoleic (AA precursor) acids also decreased. As evidenced by histology, main changes in testes matched the appearance of spermatids and first spermatozoa, at the end of meiotic divisions. In milt, no variations were appreciated and PUFAs were the most abundant fatty acids, close to 50%. Due to their increase in testes and the high concentration in milt, PUFAs probably play an important role in the sexual maturation of European eel. Further research is necessary to determine the relationship between feeding, fatty acids and sperm quality.