Follicle stimulating hormone (FSH) and luteinizing hormone (LH) gene expression during larval development in Senegalese sole (Solea senegalensis)

The gonadotropins (GTHs), follicle stimulating hormone (FSH) and luteinizing hormone (LH), determine the reproductive competence of adult breeders, but also participate in the establishment of the reproductive axis at early stages of life. The present study aimed at studying, by real-time qPCR, the gene expression levels of GTH subunits (FSH beta, LH beta and the common glycoprotein alpha -GP alpha- subunit) during early development in Senegalese sole, from I to 100 days post hatching (dph). The FSH beta, LH beta and GP alpha transcripts were first detected at 1, 5 and 3 dph, respectively. Transcript levels of FSH beta, and GP alpha, increased continuously to peak levels at mid metamorphosis (15 dph), decreasing thereafter; levels were maintained low until a second increment detected at 90 and 100 dph. Contrarily, transcript levels of LH beta were very low and only detectable around metamorphosis. All three subunits were highly expressed in 1-year old soles, with FSH beta and GP alpha transcript levels 10-fold higher than those of LH beta. These results suggest, i) activity of the reproductive axis early after hatching (1 dph), which was highest during the metamorphic climax and, ii) a predominant role of FSH, rather than LH, in the early development of the reproductive axis in Senegalese sole. (C) 2009 Elsevier Inc. All rights reserved.