Anoxia tolerance in the sea cucumbers Parastichopus californicus and Cucumaria miniata reflects habitat use

Abstract

Abstract Natural fluctuations in dissolved oxygen are an important physiological challenge faced by marine organisms. This is particularly true of intertidal species that may become trapped in bodies of water where oxygen becomes rapidly depleted, or which may be emersed and exposed to elevated oxygen, but without respiratory organs adapted for uptake of oxygen from air. We sought to determine whether oxygen handling approaches differ in two species of sea cucumber, Cucumaria miniata and Parastichopus californicus, which inhabit distinct niches that vary in dissolved oxygen profiles. C. miniata occupies the rocky intertidal zone and thus experiences daily oscillations in oxygen content, whereas P. californicus inhabits the more oxygen stable, subtidal zone. Using closed chamber respirometry, our data showed that C. miniata have a higher basal metabolic rate than P. californicus, attributed to continuous filter-feeding, a phenomenon that contrasts with the sporadic feeding habits of the sediment-feeding P. californicus. Exposure to 6-h of anoxia or 6-h of emersion had no effect on coelomic fluid glucose concentrations in either species, however P. californicus body wall glucose concentrations increased ~6-fold relative to immersed normoxic controls under both treatments. Lactate production, a marker of anaerobic metabolism, was unaltered in both species under both anoxia and emersion conditions. These data demonstrate that habitat influences anoxia tolerance in sea cucumbers, with the intertidal C. miniata displaying a higher tolerance to both low dissolved oxygen and emersion, than the subtidal species, P. californicus.