Physiological and behavioral responses to hypoxia and hydrogen sulfide in the infaunal asteroid Ctenodiscus crispatus
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- Shick, J.M. Mar. Biol. (1976) 37: 279. doi:10.1007/BF00387613
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Survival of Ctenodiscus crispatus during exposure to hypoxia (PO2<3 mm Hg) at 5°C is greater than that of any echinoderm reported in the literature, the LT50 being 248 h; this is reduced to 236 h in the presence of hydrogen sulfide. Unlike Asterias vulgaris and A. forbesi, both of which lose the tube foot response to tactile stimulation long before death from hypoxia occurs, C. crispatus remains responsive until death. The extension of the highly protrusible epiproctal cone, which occurs in 75% of the mud stars simultaneously exposed to hypoxia and H2S, serves to maintain burrow contact with the overlying water. The rate of oxygen consumption remains constant down to an ambient oxygen partial pressure of 10 to 25 mm Hg, becoming more oxygen-dependent after prior exposure of the asteroids to hypoxia. C. crispatus exhibits a clear oxygen-debt phenomenon as well as a compensatory reduction in the residual PO2 (oxygen partial pressure at which oxygen consumption ceases) from 2.4 to 0.2 mm Hg after hypoxic exposure.