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‐tolerant Astronotus spp. Issue 9 (2nd August 2021)

• Record Type: Journal Article
• Authors: Braz‐Mota, Susana; Almeida‐Val, Vera M. F.
• Other Names: Pelster Bernd guestEditor.; Val Adalberto L. guestEditor.
• Is Part Of: Journal of experimental zoology. Volume 335:Issue 9/10(2021)
• Page Start: 771
• Page End: 786
• Publication Date: 2021-08-02
• Subjects: anaerobic survival -- fish -- gill remodeling -- hypoxia -- signaling pathways -- tolerance; Zoology -- Periodicals; Zoology; Animal Population Groups -- physiology; Zoology; Electronic journals; Periodical; Periodicals; 590
• DOI: 10.1002/jez.2531
• Languages: English
• ISSNs: 2471-5646

Abstract

Abstract: 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. Abstract : Central responses mechanisms of the hypoxia‐tolerant fish Astronotus spp. cope with frequent hypoxia and anoxia. Highlights: Amazonian fish have ecological adaptations acquired during evolution that provide them with phenotypic plasticity. The exceptional hypoxia tolerance of Astronotus spp. is facilitated by a pronounced anaerobic survival involving a coordinated response in many tissues. Astronotus spp. have a refined osmorespiratory compromise under hypoxia saving energy by the reduction of ionic fluxes and adjustments in respiratory control. Astronotus spp. uncouple their mitochondria at the same time they increase anaerobic metabolism to produce ATP anaerobically.