The Oxidative Detoxification And Metabolic Adaptation Of Urechis Unicinctus To Sulfide

Although sulfide is generally considered to be a highly toxic substance for aerobic organisms, various species of animals are found to inhabit sulfidic environments such as hydrothermal vents, cold seeps, and coastal mud flats. Urechis unicinctus subjected to Echiuroidea, Echiurida, Xenopneusta, Urechidae, Urechis inhabits intertidal or subtidal mud flats and may encounter sulfide exposure in its habitat. In this paper, the tolerance, oxidative detoxification and metabolic adaptation of this worm to sulfide were investigated with methods of experimental ecology, analysis of sulfide oxidation products, assay of metabolic enzymes activities and cytology. The aims of this study are to reveal its physiological and metabolic responses to sulfide and provide an academic evidence for bioremediation of polluted sediment.Firstly, survival of the worm was tested at different concentrations of sulfide. During the test, no worm died in the control without sulfide. The survivorship of experimental worms exposed to 50 or 150μM sulfide was affected 48 h after exposure. In presence of 300 or 600μM sulfide, animal death was observed 24 h after exposure. The median lethal time (LT₅₀) was 112 h, 86 h, 68 h, 60 h at 50, 150, 300 and 600μM concentrations of sulfide, respectively. The result indicates Urechis unicinctus is moderately sulfide-tolerant and tolerance low concentrations of sulfide (≤50μM) well but its ability to tolerance high concentrations of sulfide (150⁶00μM) is relatively lower. The method of reverse high performance liquid chromatogram was used to detect possible sulfide oxidation products in body wall and hindgut of the worm during sulfide exposure and after removal of sulfide exposure. The result showed that high concentrations of sulfite and thiosulfate were found in body wall and hindgut of worms exposed to sulfide, but these sulfur compounds were absent or unchanged in control worms. The concentration of sulfite and thiosulfate in body wall and hindgut of worms exposed to sulfide increased significantly at 2 h. During 50μM sulfide exposure, the concentration of sulfite in hindgut reached a maximum 959.85±29.42μmol kg-1wm...