Rapid mitochondrial adjustments in response to short-term hypoxia and re-oxygenation in the Pacific oysterCrassostrea gigas

Abstract

SUMMARYAs oxygen concentrations in marine coastal habitats can fluctuate rapidly and drastically, sessile marine organisms such as the oyster Crassostrea gigas can experience marked and rapid oxygen variations. In this study, we investigated the responses of oyster gill mitochondria to short-term hypoxia (3 and 12h, at 1.7mgO 2 l Supplementary material available online at

Hypoxia-cadmium interactions on rainbow trout (Oncorhynchus mykiss) mitochondrial bioenergetics: attenuation of hypoxia-induced proton leak by low doses of cadmium

“…1), the rainbow trout mitochondria became markedly uncoupled (reduced RCR) and inefficient (reduced P/O ratio) in line with previous findings in hypoxia-sensitive mammalian mitochondria (Gnaiger et al, 2000;Blomgren et al, 2003;Kim et al, 2003;Navet et al, 2006;Hoffman et al, 2007). In contrast, mitochondria from hypoxia-tolerant species maintain or increase the phosphorylation efficiency and coupling following hypoxia/reoxygenation (Storey and Storey, 1990;Kurochkin et al, 2009;Ivanina et al, 2012;Sussarellu et al, 2013). Thus these disparate responses are defensible, in part, based on hypoxia tolerance/sensitivity of the experimental animal species employed in various studies.…”

“…The clearly elevated state 4/4 ol respiration observed following hypoxia and reoxygenation of rainbow trout liver mitochondria is in stark contrast with the findings in hypoxia-resistant species such as oysters, in which hypoxia/reoxygenation in seawater reduced state 4 respiration Ivanina et al, 2012;Sussarellu et al, 2013). Our results are nonetheless similar to those obtained following 6 days of anoxia by air exposure (Kurochkin et al, 2009), which show that state 4 respiration was elevated within the first 6 h of post-anoxia reoxygenation.…”

“…In contrast, studies carried out in vivo with hypoxia-resistant species such as oysters show both similarities and differences with the results obtained in the present study. Whereas reduced mitochondrial state 3 respiration occurs following both long-term (Ivanina et al, 2012) and short-term (Sussarellu et al, 2013) in vivo hypoxia exposure and reoxygenation in seawater, Kurochkin et al (Kurochkin et al, 2009) observed a significant state 3 respiration overshoot relative to normoxic controls within the first 1-6 h of reoxygenation following air-exposure-induced anoxia in the same species. This overshoot, thought to assist oysters in recovery from the oxygen debt and attendant energy (ATP) deficit incurred during the anoxic period, is apparently non-existent in mitochondria from rainbow trout and probably other hypoxia-sensitive species.…”

“…Our results are nonetheless similar to those obtained following 6 days of anoxia by air exposure (Kurochkin et al, 2009), which show that state 4 respiration was elevated within the first 6 h of post-anoxia reoxygenation. Sussarellu et al (Sussarellu et al, 2013) speculated that oysters employ different mechanisms to adjust energy metabolism depending on how hypoxia is experienced, i.e. via low dissolved oxygen in seawater or by air exposure.…”

“…While it is apparent that both hypoxia and Cd impact energy homeostasis as single stressors, our knowledge of their interactions is limited to very few studies on hypoxia-tolerant aquatic species, carp and oysters (Hattink et al, 2005;Kurochkin et al, 2009;Ivanina et al, 2012;Sussarellu et al, 2013). These interaction studies showed that while hypoxia-tolerant species are able to withstand the effect of hypoxia on mitochondrial function, concurrent Cd and hypoxia exposure increased the Cd burden (relative to Cd alone exposure) in oysters (Kurochkin et al, 2009) but not in carp (Hattink et al, 2005), suggesting that different organisms respond to hypoxia and metals exposure differently.…”