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1 Marine Fish Nutrition Team, Nutrition Aquaculture and Genomics Research Unit, UMR 1067, Ifremer, PLOUZANE, France
2 PLOUZANE, France; Marine Fish Nutrition Team, Nutrition Aquaculture and Genomics Research Unit, UMR 1067, Ifremer, PLOUZANE, France
* To whom correspondence should be addressed. E-mail: jlzambon{at}ifremer.fr.
The influence of dietary vitamins on growth, survival and morphogenesis was evaluated until day 38 of post-hatching life in European sea bass larvae (Dicentrarchus labrax). A standard vitamin mix (at double the concentration of NRC recommendations) was incorporated into larval feeds at 0.5%, 1.5%, 2.5%, 4.0% and 8.0% to give treatments VM 0.5, VM 1.5, VM 2.5, VM 4.0 and VM 8.0 respectively. The group fed the VM 0.5 diet all died before day 30. At day 38, the larvae group fed VM 1.5 had 33% survival while the other groups, with higher vitamin levels, showed at least 50% survival. The higher the percentage vitamin mix in the diet, the lower the percentage of column deformities. High dietary vitamin levels positively influenced the formation of mineralized bone in larvae: the higher the dietary vitamin level, the higher the ossification status. In the larvae group fed at the highest vitamin levels, we observed a temporal sequence of co-ordinated growth factor expression where the expression of BMP-4 (Bone Morphometric Protein) preceded the expression of IGF-1 (Insulin Growth Factor), which stimulated the maturation of osteoblasts (revealed by high osteocalcin expression levels). In groups fed lower proportions of vitamins, elevated PPAR-
(Proliferator Peroxisome Activated Receptors) expression coincided with low BMP-4 expression. Our results suggest that high levels of PPAR-
transcripts in larvae fed diets with a low vitamin mix content converted some osteoblasts into adipocytes during the 2 first weeks of life. This loss of osteoblasts is likely to have caused skeletal deformities.
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