Biochemical changes during
the embryonic development of Norway lobster, Nephrops norvegicus
R.
Rosa, S. Morais, R. Calado, L. Narciso, M.L. Nunes-2003
Aquaculture, 221(1-4): 507-522
Abstract:
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.