Histological studies on Halicryptus spinulosus (Priapulida) with regard to environmental hydrogen sulfide resistance

The priapulid Halicryptus spinulosus has an outstanding resistance to anoxia and hydrogen sulfide, which enables the animal to survive in deteriorating environments. Whole-body staining procedures, as well as light and scanning electron microscopy were used to study structures and mechanisms possibly involved in sulfide detoxification.The cuticle of the trunk is covered by a coat of mucus and bacteria. Within this coat considerable amounts of finely dispersed iron are precipitated, probably as a Fe²⁺-compound. It is suggested that the iron functions as a rechargeable buffer against hydrogen sulfide, protecting both the bacteria and the priapulid host. Although this chemical shield may not alone account for long-term protection, it allows the animal to gain time for metabolic adaptations.Contribution No. 289 of the Alfred-Wegener-Institut für Polar- and Meeresforschung (AWI Bremerhaven).