Are all bony fishes oxygen regulators? Evidence for oxygen regulation in a putative oxygen conformer, the swamp eel <i>Synbranchus marmoratus</i>

Svendsen, Morten Bo Søndergaard; Johansen, Jacob L.; Bushnell, Peter G.; Skov, Peter Vilhelm; Norin, Tommy; Domenici, Paolo; Steffensen, John F.; Abe, Augusto Shinya

doi:10.1111/jfb.13861

Cited by 5 publications

(2 citation statements)

References 64 publications

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“…If severe enough, acute hypoxia constrains blood oxygenation at the gills in fish, which may compromise tissue O 2 delivery and aerobic metabolism (Boutilier, 2001;Butler and Taylor, 1975;Chan, 1986;Holeton and Randall, 1967;Powell et al, 2000;Stecyk, 2017;Steffensen and Farrell, 1998). Most fish, however, are 'O 2 regulators', meaning that they adjust cardiorespiratory functions (cardiovascular and metabolic) to maintain a stable O 2 consumption rate (ṀO 2 , a proxy for aerobic metabolic rate) over a range of speciesspecific hypoxic Pw O2 values (Svendsen et al, 2019). At a specific critical Pw O2 (P crit ), however, cardiorespiratory adjustments are no longer sufficient to compensate for increasingly lower O 2 diffusion gradients, and a transition from O 2 regulation to O 2 conformation occurs, which is marked by a progressive decline in ṀO 2 (Rogers et al, 2016;Ultsch and Regan, 2019).…”

Section: Introductionmentioning

confidence: 99%

Cardiorespiratory adjustments to chronic environmental warming improve hypoxia tolerance in European perch (Perca fluviatilis)

Ekström

Sundell

Morgenroth

et al. 2021

Journal of Experimental Biology

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Aquatic hypoxia will become increasingly prevalent in the future due to eutrophication combined with climate warming. While short-term warming typically constrains fish hypoxia tolerance, many fishes cope with warming by adjusting physiological traits through thermal acclimation. Yet, little is known about how such adjustments affect tolerance to hypoxia.We examined European perch (Perca fluviatilis) from the Biotest enclosure (23°C, Biotest population), a unique ∼1 km2 ecosystem artificially warmed by cooling water from a nuclear power plant, and an adjacent reference site (16-18°C, Reference population). Specifically, we evaluated how acute and chronic warming affect routine oxygen consumption rate (MO2routine) and cardiovascular performance in acute hypoxia, alongside assessments of the thermal acclimation of the aerobic contribution to hypoxia tolerance (critical O2 tension for MO2routine; Pcrit) and absolute hypoxia tolerance (O2 tension at loss of equilibrium; PLOE).Chronic adjustments (possibly across lifetime or generations) alleviated energetic costs of warming in Biotest perch by depressing MO2routine and cardiac output, and by increasing blood O2 carrying capacity relative to reference perch acutely warmed to 23°C. These adjustments were associated with improved maintenance of cardiovascular function and MO2routine in hypoxia (i.e., reduced Pcrit). However, while Pcrit was only partially thermally compensated in Biotest perch, they had superior absolute hypoxia tolerance (i.e., lowest PLOE) relative to reference perch irrespective of temperature.We show that European perch can thermally adjust physiological traits to safeguard and even improve hypoxia tolerance during chronic environmental warming. This points to cautious optimism that eurythermal fish species may be resilient to the imposition of impaired hypoxia tolerance with climate warming.

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Section: Introductionmentioning

confidence: 99%

Cardiorespiratory adjustments to chronic environmental warming improve hypoxia tolerance in European perch (Perca fluviatilis)

Ekström

Sundell

Morgenroth

et al. 2021

Journal of Experimental Biology

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“…While Hu et al . (2014) did not exercise the squid in their experiments, it is likely that a measurement period of 20–30 minutes may not have allowed for a true Ṁ O 2Routine measurement due to the handling stress and introduction to the respirometry chamber (Keys, 1930; Svendsen et al ., 2018). Nevertheless, considering all animals were handled and introduced to the chambers in the same way, the comparisons among CO 2 treatments from the previous experiment are still useful.…”

Section: Discussionmentioning

confidence: 99%

Aerobic performance of two tropical cephalopod species unaltered by prolonged exposure to projected future carbon dioxide levels

Spady

Nay

Rummer

et al. 2019

Conservation Physiology

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Ecological adaptations of Amazonian fishes acquired during evolution under environmental variations in dissolved oxygen: A review of responses to hypoxia in fishes, featuring the hypoxia‐tolerantAstronotusspp.

Braz-Mota

Almeida-Val

2021

J Exp Zool Pt A

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The Amazon Basin presents a dynamic regime of dissolved oxygen (DO) oscillations, which varies among habitats within the basin, including spatially, daily, and seasonally. Fish species inhabiting these environments have developed many physiological adaptations to deal with the frequent and periodic events of low (hypoxia), or no (anoxia) DO in the water. Cichlid fishes, especially the genus Astronotus (A. ocellatus and A. crassipinnis), are hypoxic‐tolerant species that can survive in very low DO levels for long periods, while adults often inhabit places where DO is close to zero. The present review will focus on some metabolic adjustments that Amazonian fish use in response to hypoxic conditions, which include many strategies from behavioral, morphological, physiological, and biochemical strategies. These strategies include ASR (aerial surface respiration), lip expansion, branchial tissue remodeling, increases in glycolytic metabolism with the increase of blood glucose levels, and increases in anaerobic metabolism with increases of plasma lactate levels. Other groups over evolutionary time developed obligate aerial respiration with changes in pharyngeal and swim bladder vascularization as well as the development of a true lung. However, most species are water‐breathing species, such as A. ocellatus and A. crassipinnis, which are detailed in this study because they are used as hypoxia‐tolerant model fish. Herein, we draw together the literature data of the physiological mechanisms by which these species decrease aerobic metabolism and increase anaerobic metabolism to survive hypoxia. This is the first attempt to synthesize the physiological mechanisms of the hypoxia‐tolerant Astronotus species.

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Are all bony fishes oxygen regulators? Evidence for oxygen regulation in a putative oxygen conformer, the swamp eel Synbranchus marmoratus

Cited by 5 publications

References 64 publications

Cardiorespiratory adjustments to chronic environmental warming improve hypoxia tolerance in European perch (Perca fluviatilis)

Cardiorespiratory adjustments to chronic environmental warming improve hypoxia tolerance in European perch (Perca fluviatilis)

Aerobic performance of two tropical cephalopod species unaltered by prolonged exposure to projected future carbon dioxide levels

Ecological adaptations of Amazonian fishes acquired during evolution under environmental variations in dissolved oxygen: A review of responses to hypoxia in fishes, featuring the hypoxia‐tolerantAstronotusspp.

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