Expression of TRH, TSH and TH receptors during larval development. Gene expression levels (log2), from 1 to 33 dph, of S. solea transcripts codifying key genes of the TH cascade. A. S. solea TRH, TSH and D1 transcripts; B. S. solea THRαA and THRαB transcripts. Graphics show mean gene expression measured with microarray, bars indicate standard deviation (SD) across biological replicates. Statistical significance (p < 0.05) when comparing one larval stage against the previous one is indicated by asterisk (*).