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Sulfide detoxification and tolerance in Halicryptus spinulosus (Priapulida): a multiple strategy

1992; Inter-Research; Volume: 86; Linguagem: Inglês

10.3354/meps086167

1616-1599

Rolf Oeschger, RD Vetter,

Parasite Biology and Host Interactions

The detoxificahon potential of Halicryptus spinulosus in the presence of sulfide was studied.The worms are able to cope with considerable amounts of sulfide.They benefit from several survival strategies for controlling sulfide dose and detoxifying sulfide that enters the body.When oxygen and sulfide occur concurrently in the environment sulfide can either initially b e excluded or internal concentration kept low by the animals.Non-toxic thlosulfate, the main detoxification product, accumulates up to 3856 f 997 pM in the hemolymph.Sulfide has an overriding influence on the aerobic metabolism and imposes anaerobiosis even though oxygen is available, i.e. sulfide-induced anaerobiosis.Succinate, a n indicator of anaerobic metabolism, accumulates during persistent oxic sulfide incubation to 12.3 f 2.3 pm01 ml-' in hemolymph and to 3.0 2 1.3 pm01 g-' fresh mass in body wall after 10 d.During anoxic sulfide exposure, the animals make use of graded strateqes.Some sulfide is immobilised in an external barrier due to iron-sulfide formation.The iron-sulfide compound results in a conspicuous blackening of the animal and its blood.This blackemng is fully reversible upon receiving oxygen again.Detoxification to thiosulfate, depending on the oxygen storage capacity of the hemolymph, amounted to only a minor level, with a maximum of 172 f 49 WM in the hemolymph after l d of incubation.Sulfide also binds to a presently unknown hemolymphic factor.This binding may temporarily protect mitochondna, a main location of sulfide detoxification.The mitochondrial enzyme for aerobic metabolism, cytochrome c oxidase, is inhibited by low sulfide levels in vitro (K, 1.05 _t 0.22 PM), and has a much higher in vivo resistance in whole anlmals.Catalase, another sulfide sensitive enzyme, has a K, of ca 200 FM In vitro and is unaffected in vivo.Internal sulfide concentration in the hemolymph increases ca 3-fold (570 + 298pM) over external levels during long-tern~ exposure experiments with 200 pM sulfide.The survival in spite of such a n elevated amount of internal sulfide accumulation is unprecedented for a marine invertebrate without endosymbionts.The worms can passively outlast raised environmental sulfide concentrations by their high capacity for anaerobic metabolism.