Résumé
The purpose of this study was to examine the effects of vitamin A levels in the larval diet of Dicentrarchus labrax, (a) on the shape of juvenile skeleton and (b) on the development of pelvic fins. To exclude the side-effects of skeletal abnormalities on skeleton shape, morphometric analysis was performed on normal individuals only. Geometric morphometric analysis revealed a significant effect of larval nutrition on the shape of juvenile skeleton (Wilk's lambda=0.0188, P < 0.001), 55 days after the application of the different nutritional regimes. Between-groups shape differences mainly concerned the position of anterior dorsal pterygiophore, which was associated with a significant (P < 0.05) increase of the number of dorsal lepidotrichia and hard spines at low levels of vitamin A (3-9 x 103 IU kg-1 dry food). At the lowest vitamin A levels (3 x 103 IU kg-1 dry food), the development of pelvic fins was abnormal, with severe bilateral (44 +/- 10%, mean +/- SD) or unilateral (22 +/- 9%) lack of the fin lepidotrichia, hard spines and their supporting elements. In the 82-94% of the unilaterally deformed individuals, deformation concerned the left pelvic fin. Concerning the shape of pelvic fins in the normally developed individuals, results demonstrated a significant effect of nutritional conditions on the size and position of all the elements of the pelvic fin area (basipterygium, lower metacleithrum, cleithrum, scapula) (Wilk's lambda=0.3087, P < 0.001). Our results demonstrate a significant nutritionally driven phenotypic plasticity in D. labrax, with dietary levels of vitamin A determining the skeleton shape and the left-right symmetry of pelvic fins.