Journal ArticleDOI
Excretory nitrogen metabolism and defence against ammonia toxicity in air-breathing fishes.
Shit F. Chew,Yuen K. Ip +1 more
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TLDR
The responses of air-breathing fishes to ameliorate ammonia toxicity are many and varied, determined by the behaviour of the species and the nature of the environment in which it lives.Abstract:
With the development of air-breathing capabilities, some fishes can emerge from water, make excursions onto land or even burrow into mud during droughts. Air-breathing fishes have modified gill morphology and morphometry and accessory breathing organs, which would tend to reduce branchial ammonia excretion. As ammonia is toxic, air-breathing fishes, especially amphibious ones, are equipped with various strategies to ameliorate ammonia toxicity during emersion or ammonia exposure. These strategies can be categorized into (1) enhancement of ammonia excretion and reduction of ammonia entry, (2) conversion of ammonia to a less toxic product for accumulation and subsequent excretion, (3) reduction of ammonia production and avoidance of ammonia accumulation and (4) tolerance of ammonia at cellular and tissue levels. Active ammonia excretion, operating in conjunction with lowering of ambient pH and reduction in branchial and cutaneous NH₃ permeability, is theoretically the most effective strategy to maintain low internal ammonia concentrations. NH₃ volatilization involves the alkalization of certain epithelial surfaces and requires mechanisms to prevent NH₃ back flux. Urea synthesis is an energy-intensive process and hence uncommon among air-breathing teleosts. Aestivating African lungfishes detoxify ammonia to urea and the accumulated urea is excreted following arousal. Reduction in ammonia production is achieved in some air-breathing fishes through suppression of amino acid catabolism and proteolysis, or through partial amino acid catabolism leading to alanine formation. Others can slow down ammonia accumulation through increased glutamine synthesis in the liver and muscle. Yet, some others develop high tolerance of ammonia at cellular and tissue levels, including tissues in the brain. In summary, the responses of air-breathing fishes to ameliorate ammonia toxicity are many and varied, determined by the behaviour of the species and the nature of the environment in which it lives.read more
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Journal ArticleDOI
Amphibious fishes: evolution and phenotypic plasticity.
Patricia A. Wright,Andy J. Turko +1 more
TL;DR: The use of phenotypic plasticity by amphibious fishes is reviewed and whether studying plasticity in extant fishes can provide insight into evolutionary changes during the tetrapod invasion of land is asked.
Journal ArticleDOI
The Lungfish Transcriptome: A Glimpse into Molecular Evolution Events at the Transition from Water to Land.
Maria Assunta Biscotti,Marco Gerdol,Adriana Canapa,Mariko Forconi,Ettore Olmo,Alberto Pallavicini,Marco Barucca,Manfred Schartl +7 more
TL;DR: It is indicated that lungfish, not coelacanths, are the closest relatives to land-adapted vertebrates and transposable elements appear to be active and show high diversity, suggesting a role for them in the remarkable expansion of the lungfish genome.
Journal ArticleDOI
Air‐breathing fishes in aquaculture. What can we learn from physiology?
Sjannie Lefevre,Tobias Wang,A. Jensen,Nguyen Van Cong,Do Thi Thanh Huong,Nguyen Thanh Phuong,Mark Bayley +6 more
TL;DR: It is argued that an understanding of air-breathing fishes' respiratory physiology, including metabolic rate, partitioning of oxygen uptake from air and water in facultative air breathers, the critical oxygen tension, can provide important input for the optimization of culture practices.
Journal ArticleDOI
Growth, oxidative stress responses, and gene transcription of juvenile bighead carp (Hypophthalmichthys nobilis) under chronic-term exposure of ammonia.
TL;DR: The data clearly demonstrate that chronic exposure of UIA at lower concentrations can result in some degree of impairment of antioxidative function, and chronic exposure at higher concentrations can enhance damage to juvenile bighead carp by modulating antioxidant enzyme activities and gene transcription.
Journal ArticleDOI
Are Amazonian fish more sensitive to ammonia? Toxicity of ammonia to eleven native species
TL;DR: Results confirm the hypothesis that Amazonian fish are more sensitive to ammonia than other freshwater species and indicate that further studies incorporating hypoxia and air access/denial are needed.
References
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Journal ArticleDOI
The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste
TL;DR: The fish gill is a multipurpose organ that, in addition to providing for aquatic gas exchange, plays dominant roles in osmotic and ionic regulation, acid-base regulation, and excretion of nitrogenous wastes.
Journal ArticleDOI
Ammonia toxicity in fish
D.J Randall,T.K.N Tsui +1 more
TL;DR: Fish have strategies to protect them from the ammonia pulse following feeding, and this also protects them from increases in external ammonia, as a result starved fish are more sensitive to external ammonia than fed fish.
Journal ArticleDOI
The ABC protein turned chloride channel whose failure causes cystic fibrosis
TL;DR: New structural and biochemical information from prokaryotic ABC proteins and functional information from CFTR channels has led to a unifying mechanism explaining those ATP-driven conformational changes.
Journal ArticleDOI
Neurobiology of ammonia
TL;DR: Therapy in hyperammonemic syndromes continues to rely on ammonia-lowering strategies via peripheral mechanisms (reduction of ammonia production in the gastrointestinal tract, increased ammonia removal by muscle).
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