Five P. fulvidraco rxr (Pf-rxr) subtypes differed in the length of cDNA sequence and the open reading
frame, but shared the similar domain structures as in typical nuclear receptors. Phylogenetic analysis
revealed that the five Pf-rxr subtypes were paralogous genes, and that Pf-rxrba and Pf-rxrbb had arisen
during a teleost-specific genome duplication event.