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dc.contributor.authorLopes, Ana Ritapt_PT
dc.contributor.authorTrübenbach, Katjapt_PT
dc.contributor.authorTeixeira, Tatianapt_PT
dc.contributor.authorLopes, Vanessa M.pt_PT
dc.contributor.authorPires, Vanessapt_PT
dc.contributor.authorBaptista, Miguelpt_PT
dc.contributor.authorRepolho, Tiagopt_PT
dc.contributor.authorCalado, Ricardopt_PT
dc.contributor.authorDiniz, Máriopt_PT
dc.contributor.authorRosa, Ruipt_PT
dc.description.abstractDiel vertical migrators, such as myctophid fishes, are known to encounter oxygen minimum zones (OMZ) during daytime in the Eastern Pacific Ocean and, therefore, have to cope with temperature and oxidative stress that arise while ascending to warmer, normoxic surface waters at night-time. The aim of this study was to investigate the antioxidant defense strategies and heat shock response (HSR) in two myctophid species, namely Triphoturus mexicanus and Benthosema panamense, at shallow and warm surface waters (21. kPa, 20-25. °C) and at hypoxic, cold (≤1. kPa, 10. °C) mesopelagic depths. More specifically, we quantified (i) heat shock protein concentrations (HSP70/HSC70) (ii) antioxidant enzyme activities [including superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST)], and (iii) lipid peroxidation [malondialdehyde (MDA) levels]. HSP70/HSC70 levels increased in both myctophid species at warmer, well-oxygenated surface waters probably to prevent cellular damage (oxidative stress) due to increased oxygen demand under elevated temperatures and reactive oxygen species (ROS) formation. On the other hand, CAT and GST activities were augmented under hypoxic conditions, probably as preparatory response to a burst of oxyradicals during the reoxygenation phase (while ascending). SOD activity decreased under hypoxia in B. panamense, but was kept unchanged in T. mexicanus. MDA levels in B. panamense did not change between the surface and deep-sea conditions, whereas T. mexicanus showed elevated MDA and HSP70/HSC70 concentrations at warmer surface waters. This indicated that T. mexicanus seems to be not so well tuned to temperature and oxidative stress associated to diel vertical migrations. The understanding of such physiological strategies that are linked to oxygen deprivation and reoxygenation phases may provide valuable information about how different species might respond to the impacts of environmental stressors (e.g. expanding mesopelagic hypoxia) coupled with global climate change.pt_PT
dc.description.sponsorshipThe authors would like to thank Brad Seibel for making the participation in the research cruise aboard RV New Horizon possible and Unai Markaida for his assistance on the collection and identification of myctophids. The Portuguese Foundation for Science and Technology (FCT) supported this study through a Senior Research Position Ciência 2007 to R.R and RC and Ciência 2008 to M.D.pt_PT
dc.subjectAntioxidant defense systempt_PT
dc.subjectBenthosema panamensept_PT
dc.subjectHeat shock responsept_PT
dc.subjectOxidative stresspt_PT
dc.subjectOxygen minimum zonespt_PT
dc.subjectTriphoturus mexicanuspt_PT
dc.titleOxidative stress in deep scattering layers: heat shock response and antioxidant enzymes activities of myctophid fishes thriving in oxygen minimum zonespt_PT
degois.publication.titleDeep Sea Research Part I: Oceanographic Research Paperspt_PT
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