Fugu Mstn profiles. A) Genome structure of fugu Mstn gene (1905 bp). Black boxes, exons (with the Roman numeral representing the number of exons) and bars, introns. B) Sequence alignment of fugu [GenBank, ADT89782], medaka [GenBank, NP_001188428] and bovine [GenBank, NP_001001525] Mstn protein. Amino acids conserved across the three species are outlined in red. The amino-acid sequence of fugu Mstn shows 83.8% and 60.1% identity to that of medaka and bovine, respectively. The C-terminal peptide, which is considered to be significant for the function, is outlined in light blue. The underlined cysteines are essential for the activity of Mstn in vertebrate. The fugu C-terminal region has an 88.1% identity to medaka and bovine Mstn. Black triangle, the amino acid responsible for the loss-of-function phenotype in medaka and bovine. Bidirectional bold and thin arrows (A) and bold characters (B), the region examined by the HRM analysis in this study.