Bathymodiolus septemdierum inhabiting deep-sea hydrothermal vent area have been suggested to use hypotaurine, a precursor of taurine, to avoid the toxicity of hydrogen sulfide contained in the seawater from the vent. In this system, it is important to accumulate hypotaurine in the gill, which is the primary site of sulfide exposure. However, the pathway for hypotaurine synthesis has not reported in mollusks. To elucidate genes related hypotaurine synthesis pathway, we conducted transcriptome sequencing of gill tissue in Bathymodiolus septemdirum with 454 FLX Titanium.