Different sizes of the mangrove mud clam Anodontia edentula were collected from the mangroves in Brgy. San Roque in Estancia, Iloilo, central Philippines, and the mantle, gill, and foot tissues were analyzed for elemental sulfur content. Mangrove mud (substrate) was also analyzed for total sulfur content to establish the possibility of clam-bacteria symbiosis in this lucinid clam. Sulfur analysis showed highly significant (p <0.0001) amounts of elemental sulfur in the gills (247.64 ± 63.28 μmoles/g FW) compared with the quantities observed in the mantle (0.84 ± 0.22 μmoles/g FW). Elemental sulfur was absent from the foot tissues. Results also showed a significantly (p <0.05) decreasing elemental sulfur from the newly collected clams (mean = 461.18 μmoles/g FW) compared to those reared in the laboratory (mean = 159.08 μmoles/g FW: with mangrove mud substrate; mean = 45.18 μmoles/g FW without substrate), which were analyzed weekly until week 3, indicating that stored elemental sulfur is being utilized by the bacteria in the absence of sulfide. Total sulfur content of mangrove mud in situ was higher than that used us substrate in the experiment; where there were no significant differences from initial to final readings. This shows that mangrove mud in situ is linked to a steady sulfur source.