Evolution of tissue composition and serum metabolites during gonadal development in the common dentex ( Dentex dentex)

Abstract

This study describes the evolution of tissue composition and serum metabolites of common dentex ( Dentex dentex) in different maturity stages. During maturation, diet and perivisceral fat provide the materials needed for the development of gonads. Female and male fish had higher total proteins, total fat, triglycerides (TG) and cholesterol in their serum, at spawning and spermiation, respectively. The examination of dentex tissues (muscle, liver and gonad) revealed no statistically significant differences ( P<0.05) in energy density and lipid content during different maturity stages and there was no conclusive evidence that energy density and lipid content differ between sexes. In muscle, liver and gonad triglycerides fraction, the proportion of saturated fatty acids (FA) was greater than the proportion of polyunsaturated fatty acids (PUFA), whereas the reverse observation was made (with the exception of liver) in the polar lipid (PL) fraction of the above tissues. In muscle and liver, the main polyunsaturated fatty acids ( n−3 PUFA) were docosahexaenoic (DHA, 22:6 n−3) and eicosapentaenoic (EPA, 20:5 n−3) acids. The main n−6 polyunsaturated fatty acids were linoleic (18:2 n−6) and arachidonic (20:4 n−6) acids. Palmitic (16:0) and oleic (18:1 n−9) acids were the main saturated fatty acids and monoenes, respectively. The relative concentration of the major fatty acids varied seasonally and a pattern can be seen in both mature and immature dentex. In the PL fraction of muscle, higher values of total saturated and n−3 fatty acids, palmitic acid and DHA were obtained during summer in comparison to winter samplings; this trend was also shown by the total saturated fatty acids in the TG fraction.