EFFECTS OF THE ADMINISTRATION OF A LOW ESTROGENIC FORMULATED DIET ON Sparus aurata GONADAL DIFFERENTIATION AND VITELLOGENIN GENE EXPRESSION

The effects of two different feeds have been tested on gonad development, as well as vitellogenin (Vtg) gene expression and protein synthesis, in the gilthead sea bream, Sparus aurata L. One group was fed a commercial feed containing fish meal as main protein source (FM), while the other group was fed a low-estrogenic formulated diet containing casein as main protein source (C). Gonadal development was not affected by diet, proceeding in both groups consistently with protandry of this species. The high variability found in Vtg expression could be mainly associated to the route of administration of estrogen like compounds, or to a past contamination of the fish with estrogens, that makes them more vulnerable to a new xenobiotic insult.