Biochemical changes during the embryonic development of Norway lobster, Nephrops norvegicus

The objectives of the present study were to investigate the total and free amino acid profiles and lipid dynamics (lipid classes and fatty acids) during embryogenesis of Nephrops norvegicus, in order to understand the early larval protein and lipid requirements. There was a significant increase in total essential (EAA) and nonessential amino acid (NEAA) contents during embryonic development (P<0.05). The major EAA were arginine, histidine and leucine, while the most important NEAA were glutamic acid, aspartic acid, glycine and proline. The higher percent increase occurred in respect to NEAA (19.9%), mainly due to the significant increase of glycine (51.8%) and alanine (35.1%). The free amino acid (FAA) content, especially the free nonessential amino acids (FNEAA), also increased significantly, being the quantitatively most important glycine, proline, taurine and glutamic acid. The free essential amino acids (FEAA) also revealed significant variations and the most important were arginine, lysine and leucine. A higher percent increase was attained with FNEAA (66.8%) in comparison to FEAA (49.6%), mainly due to the significant increase of homocystine (87.7%), valine (83.5%), glutamine (82.5%) and glutamic acid (76.1%). The absorption of dissolved organic compounds from seawater can explain the increase in free and total amino acid (FAA and TAA) contents, because a significant increase in the water content during development was observed (P<0.05). A substantial decrease in all neutral lipid classes (P<0.05) was observed during embryonic development, namely diacylglycerols (DAG) (97.9% of utilization), triacylglycerols (TAG) (93.2%), sterol esters (StE) (91.3%) and monoacylglycerols (MAG) (90.4%). The quantitatively most important fatty acids were the saturates (SFA) 14:0, 16:0 and 18:0, the monounsaturates (MUFA) 16:1n-7, 18:1n-9 and 18:1n-7, and the polyunsaturates (PUFA) 18:2n-6, 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3. The unsaturated fatty acids (UFA) are used up at a higher rate (54.5% of utilization) than SFA (42.8%); within the UFA, MUFA are more consumed than PUFA (59.3% and 52.7%, respectively). In terms of the utilization of individual fatty acids, there was a preferential consumption of 20:4n-3, 22:6n-3, 18:1n-9, 22:5n-3 and 16:1n-7. It is evident that N. norvegicus depends primarily on lipid reserves of the egg during early ontogeny. On the contrary, this species tends to conserve EAA and increase NEAA and FNEAA contents during embryonic development.