Western Blot showed that epigenetic control of the mouth dimorphism in P. pacificus correlates with histone 4 acetylation. This result was validated by mass spectrometry. This experiment profiled histone acetylation in the presence and absence of the histone deacetylase (HDAC) inhibitor Trichostatin A (TSA). Histone acetylation was also examined in the presence of another HDAC inhibitor (Na-butyrate), which served as an additional negative control because unlike TSA, it did not induce a phenotypic change.