Hypoxia tolerance and antioxidant defense system of juvenile jumbo squids in oxygen minimum zones |
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| Institution: | 1. Laboratório Marítimo da Guia, Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Av. Nossa Senhora do Cabo, 939, 2750-374 Cascais, Portugal;2. REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre 2829-516, Caparica, Portugal;1. Departamento de Biotecnología Marina, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Carretera Tijuana - Ensenada No. 3918, Zona Playitas, Ensenada, Baja California CP 22860, México;2. Instituto de Investigaciones Oceanológicas (IIO), Universidad Autónoma de Baja California (UABC), Carretera Ensenada-Tijuana No. 3917, Fraccionamiento Playitas, Ensenada, Baja California CP 22860, Mexico;3. Unidad Multidisciplinaria de Docencia e Investigación (UMDI), Facultad de Ciencias, Universidad Nacional Autónoma de México (UNAM), Puerto de Abrigo s/n, Sisal, Hunucma, Yucatan CP97355, Mexico;4. Unidad de Química en Sisal, Facultad de Química Universidad Nacional Autónoma de México (UNAM), Puerto de Abrigo s/n, Sisal, Hunucma, Yucatan CP97355, Mexico;1. MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia, Faculdade de Ciências da Universidade de Lisboa, Avenida Nossa Senhora do Cabo 939, 2750-374 Cascais, Portugal;2. UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal;3. Università degli Studi di Milano-Bicocca, Milano, Italy;4. University of Gdansk, Faculty of Oceanography and Geography, Poland;5. Department of Collective Behaviour, Max Planck Institute of Animal Behavior, University of Konstanz, Konstanz, Germany;6. Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Konstanz, Germany |
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| Abstract: | Jumbo squid (Dosidicus gigas) is a large oceanic squid endemic off the Eastern Tropical Pacific that undertakes diel vertical migrations into mesopelagic oxygen minimum zones. One of the expected physiological effects of such migration is the generation of reactive oxygen species (ROS) at the surface, promoted by the transition between hypoxia and reoxygenation states. The aim of this study was to investigate the energy expenditure rates and the antioxidant stress strategies of juvenile D. gigas under normoxia and hypoxia, namely by quantifying oxygen consumption rates, antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST)], heat shock protein expression (Hsp70/Hsc70), and lipid peroxidation malondialdehyde (MDA) levels]. A high significant decrease (68%) in squid’s metabolic rates was observed during hypoxia (p<0.05). This process of metabolic suppression was followed by a significant increase in Hsp70/Hsc70 expression (p<0.05), which may be interpreted as a strategy to prevent post-hypoxic oxidative damage during the squid’s night upwards migration to the surface ocean. On the other hand, in normoxia, the higher SOD and CAT activities seemed to be a strategy to cope with the reoxygenation process, and may constitute an integrated stress response at shallower depths. GST activity and MDA concentrations did not change significantly from normoxia to hypoxia (p>0.05), with the latter indicating no enhancement of lipid peroxidation (i.e. cellular damage) at the warmer and normoxic surface waters. The understanding of such physiological strategies that are linked to oxygen deprivation and reoxygenation phases may provide valuable information about how this species is quickly responding to the impacts of environmental stressors coupled with global climate change. |
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