| Summary: | International Symposium on Genetics in Aquaculture XII (ISGA XII), 21-27 June 2015, Santiago de Compostela, Spain.-- 1 page Controlling sex ratio is essential for the aquaculture industry, especially in those species with sex dimorphism for relevant productive traits. The turbot (Scophthalmus maximus), a very important fish for aquaculture industry in Europe, shows one of the largest sexual growth dimorphisms amongst marine cultured species, being the production of all female populations a desirable goal for industry. Although an important knowledge has been achieved on the genetic basis of sex determination (SD) in this species, the master SD gene remains unknown and precise information on key genes at the critical stage of sex differentiation is lacking. In the present work, we tackled the analysis of the expression profiles of 29 relevant genes related to sex differentiation from the first larval stages (60 days post fertilization, dpf) up to 135 dpf, when male and female gonads are differentiating. Also we considered the influence of three temperature regimes on the sex differentiation process. Three genes were the first to show differential expression between sexes and allowed us to sex turbot accurately at 90 dpf, considered as the time of the onset of sex differentiation: cyp19a1a, amh and vasa. Genes related to primordial germ cell (PGC) and PGC proliferation (vasa, gsdf, tdrd1) increased their expression between 75–90 dpf, and, specifically vasa and tdrd1, presented higher expression in females at more advanced stages (105 dpf). Furthermore, two genes present on the sex determining region of turbot were studied, sox2 and fxr1. Our results suggest that sox2 could be discarded as sex determining gene, while fxr1 presented an expression pattern which could be consistent with a function as sex determinant, being up-regulated in females at 105 dpf. We also detected significative changes in the expression level of several genes (for example cyp11a, dmrt2 or sox6) depending on culture temperature and our data suggest ...
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