1
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Zimmer AM. Ammonia excretion by the fish gill: discoveries and ideas that shaped our current understanding. J Comp Physiol B 2024:10.1007/s00360-024-01561-5. [PMID: 38849577 DOI: 10.1007/s00360-024-01561-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 03/06/2024] [Accepted: 05/15/2024] [Indexed: 06/09/2024]
Abstract
The fish gill serves many physiological functions, among which is the excretion of ammonia, the primary nitrogenous waste in most fishes. Although it is the end-product of nitrogen metabolism, ammonia serves many physiological functions including acting as an acid equivalent and as a counter-ion in mechanisms of ion regulation. Our current understanding of the mechanisms of ammonia excretion have been influenced by classic experimental work, clever mechanistic approaches, and modern molecular and genetic techniques. In this review, I will overview the history of the study of ammonia excretion by the gills of fishes, highlighting the important advancements that have shaped this field with a nearly 100-year history. The developmental and evolutionary implications of an ammonia and gill-dominated nitrogen regulation strategy in most fishes will also be discussed. Throughout the review, I point to areas in which more work is needed to push forward this field of research that continues to produce novel insights and discoveries that will undoubtedly shape our overall understanding of fish physiology.
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Affiliation(s)
- Alex M Zimmer
- Department of Biological Sciences, University of New Brunswick, 100 Tucker Park Road, Saint John, Saint John, New Brunswick, E2L 4L5, Canada.
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2
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Kovac A, Goss GG. Cellular mechanisms of ion and acid-base regulation in teleost gill ionocytes. J Comp Physiol B 2024:10.1007/s00360-024-01560-6. [PMID: 38761226 DOI: 10.1007/s00360-024-01560-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Revised: 04/16/2024] [Accepted: 04/27/2024] [Indexed: 05/20/2024]
Abstract
The mechanism(s) of sodium, chloride and pH regulation in teleost fishes has been the subject of intense interest for researchers over the past 100 years. The primary organ responsible for ionoregulatory homeostasis is the gill, and more specifically, gill ionocytes. Building on the theoretical and experimental research of the past, recent advances in molecular and cellular techniques in the past two decades have allowed for substantial advances in our understanding of mechanisms involved. With an increased diversity of teleost species and environmental conditions being investigated, it has become apparent that there are multiple strategies and mechanisms employed to achieve ion and acid-base homeostasis. This review will cover the historical developments in our understanding of the teleost fish gill, highlight some of the recent advances and conflicting information in our understanding of ionocyte function, and serve to identify areas that require further investigation to improve our understanding of complex cellular and molecular machineries involved in iono- and acid-base regulation.
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Affiliation(s)
- Anthony Kovac
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Greg G Goss
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
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3
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Caneos WG, Shrivastava J, Ndugwa M, De Boeck G. Physiological responses of European sea bass (Dicentrarchus labrax) exposed to increased carbon dioxide and reduced seawater salinities. Mol Biol Rep 2024; 51:496. [PMID: 38587695 DOI: 10.1007/s11033-024-09460-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 03/19/2024] [Indexed: 04/09/2024]
Abstract
BACKGROUND The iono- and osmoregulatory capacities of marine teleosts, such as European sea bass (Dicentrarchus labrax) are expected to be challenged by high carbon dioxide exposure, and the adverse effects of elevated CO2 could be amplified when such fish migrate into less buffered hypo-osmotic estuarine environments. Therefore, the effects of increased CO2 on the physiological responses of European sea bass (Dicentrarchus labrax) acclimated to 32 ppt, 10 ppt and 2.5 ppt were investigated. METHODS Following acclimation to different salinities for two weeks, fish were exposed to present-day (400 µatm) and future (1000 µatm) atmospheric CO2 for 1, 3, 7 and 21 days. Blood pH, plasma ions (Na+, K+, Cl-), branchial mRNA expression of ion transporters such as Na+/K+-ATPase (NKA), Na+/K+/2Cl- co-transporters (NKCC) and ammonia transporters (e.g. Rhesus glycoproteins Rhbg, Rhcg1 and Rhcg2) were examined to understand the iono- and osmoregulatory consequences of elevated CO2. RESULTS A transient but significant increase in the blood pH of exposed fish acclimated at 10 ppt (day 1) and 2.5 ppt (day 21) was observed possibly due to an overshoot of the blood HCO3- accumulation while a significant reduction of blood pH was observed after 21 days at 2.5ppt. However, no change was seen at 32 ppt. Generally, Na + concentration of control fish was relatively higher at 10 ppt and lower at 2.5 ppt compared to 32 ppt control group at all sampling periods. Additionally, NKA was upregulated in gill of juvenile sea bass when acclimated to lower salinities compared to 32 ppt control group. CO2 exposure generally downregulated NKA mRNA expression at 32ppt (day 1), 10 ppt (days 3, 7 and 21) and 2.5ppt (days 1 and 7) and also a significant reduction of NKCC mRNA level of the exposed fish acclimated at 32 ppt (1-3 days) and 10 ppt (7-21 days) was observed. Furthermore, Rhesus glycoproteins were generally upregulated in the fish acclimated at lower salinities indicating a higher dependance on gill ammonia excretion. Increased CO2 led to a reduced expression of Rhbg and may therefore reduce ammonia excretion rate. CONCLUSION Juvenile sea bass were relatively successful in keeping acid base balance under an ocean acidification scenario. However, this came at a cost for ionoregulation with reduced NKA, NKCC and Rhbg expression rates as a consequence.
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Affiliation(s)
- Warren G Caneos
- ECOSPHERE, Department of Biology, University of Antwerp, Groenenborgerlaan 171, Antwerp, BE-2020, Belgium.
- Fisheries Department, College of Fisheries and Aquatic Sciences, Mindanao State University-Marawi, Marawi City, 9700, Philippines.
- Department of Biological Sciences, College of Science and Mathematics, Mindanao State University-Iligan Institute of Technology, Iligan City, 9200, Philippines.
| | - Jyotsna Shrivastava
- ECOSPHERE, Department of Biology, University of Antwerp, Groenenborgerlaan 171, Antwerp, BE-2020, Belgium
| | - Moses Ndugwa
- ECOSPHERE, Department of Biology, University of Antwerp, Groenenborgerlaan 171, Antwerp, BE-2020, Belgium
| | - Gudrun De Boeck
- ECOSPHERE, Department of Biology, University of Antwerp, Groenenborgerlaan 171, Antwerp, BE-2020, Belgium
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4
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Takvam M, Wood CM, Kryvi H, Nilsen TO. Role of the kidneys in acid-base regulation and ammonia excretion in freshwater and seawater fish: implications for nephrocalcinosis. Front Physiol 2023; 14:1226068. [PMID: 37457024 PMCID: PMC10339814 DOI: 10.3389/fphys.2023.1226068] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Accepted: 06/12/2023] [Indexed: 07/18/2023] Open
Abstract
Maintaining normal pH levels in the body fluids is essential for homeostasis and represents one of the most tightly regulated physiological processes among vertebrates. Fish are generally ammoniotelic and inhabit diverse aquatic environments that present many respiratory, acidifying, alkalinizing, ionic and osmotic stressors to which they are able to adapt. They have evolved flexible strategies for the regulation of acid-base equivalents (H+, NH4 +, OH- and HCO3 -), ammonia and phosphate to cope with these stressors. The gills are the main regulatory organ, while the kidneys play an important, often overlooked accessory role in acid-base regulation. Here we outline the kidneys role in regulation of acid-base equivalents and two of the key 'urinary buffers', ammonia and phosphate, by integrating known aspects of renal physiology with recent advances in the molecular and cellular physiology of membrane transport systems in the teleost kidneys. The renal transporters (NHE3, NBC1, AE1, SLC26A6) and enzymes (V-type H+ATPase, CAc, CA IV, ammoniagenic enzymes) involved in H+ secretion, bicarbonate reabsorption, and the net excretion of acidic and basic equivalents, ammonia, and inorganic phosphate are addressed. The role of sodium-phosphate cotransporter (Slc34a2b) and rhesus (Rh) glycoproteins (ammonia channels) in conjunction with apical V-type H+ ATPase and NHE3 exchangers in these processes are also explored. Nephrocalcinosis is an inflammation-like disorder due to the precipitation of calcareous material in the kidneys, and is listed as one of the most prevalent pathologies in land-based production of salmonids in recirculating aquaculture systems. The causative links underlying the pathogenesis and etiology of nephrocalcinosis in teleosts is speculative at best, but acid-base perturbation is probably a central pathophysiological cause. Relevant risk factors associated with nephrocalcinosis are hypercapnia and hyperoxia in the culture water. These raise internal CO2 levels in the fish, triggering complex branchial and renal acid-base compensations which may promote formation of kidney stones. However, increased salt loads through the rearing water and the feed may increase the prevalence of nephrocalcinosis. An increased understanding of the kidneys role in acid-base and ion regulation and how this relates to renal diseases such as nephrocalcinosis will have applied relevance for the biologist and aquaculturist alike.
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Affiliation(s)
- Marius Takvam
- Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Chris M. Wood
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - H. Kryvi
- Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Tom O. Nilsen
- Department of Biological Sciences, University of Bergen, Bergen, Norway
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5
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Tunnah L, Turko AJ, Wright PA. Skin ionocyte density of amphibious killifishes is shaped by phenotypic plasticity and constitutive interspecific differences. J Comp Physiol B 2022; 192:701-711. [PMID: 36056931 DOI: 10.1007/s00360-022-01457-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 07/13/2022] [Accepted: 08/18/2022] [Indexed: 11/24/2022]
Abstract
When amphibious fishes are on land, gill function is reduced or eliminated and the skin is hypothesized to act as a surrogate site of ionoregulation. Skin ionocytes are present in many fishes, particularly those with amphibious life histories. We used nine closely related killifishes spanning a range of amphibiousness to first test the hypothesis that amphibious killifishes have evolved constitutively increased skin ionocyte density to promote ionoregulation on land. We found that skin ionocyte densities were constitutively higher in five of seven amphibious species examined relative to exclusively water-breathing species when fish were prevented from leaving water, strongly supporting our hypothesis. Next, to examine the scope for plasticity, we tested the hypothesis that skin ionocyte density in amphibious fishes would respond plastically to air-exposure to promote ionoregulation in terrestrial environments. We found that air-exposure induced plasticity in skin ionocyte density only in the two species classified as highly amphibious, but not in moderately amphibious species. Specifically, skin ionocyte density significantly increased in Anablepsoides hartii (168%) and Kryptolebias marmoratus (37%) following a continuous air-exposure, and only in K. marmoratus (43%) following fluctuating air-exposure. Collectively, our data suggest that highly amphibious killifishes have evolved both increased skin ionocyte density as well as skin that is more responsive to air-exposure compared to exclusively water-breathing and less amphibious species. Our findings are consistent with the idea that gaining the capacity for cutaneous ionoregulation is a key evolutionary step that enables amphibious fishes to survive on land.
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Affiliation(s)
- Louise Tunnah
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Andy J Turko
- Department of Biology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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6
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Fu CW, Horng JL, Chou MY. Fish Behavior as a Neural Proxy to Reveal Physiological States. Front Physiol 2022; 13:937432. [PMID: 35910555 PMCID: PMC9326089 DOI: 10.3389/fphys.2022.937432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 06/23/2022] [Indexed: 11/13/2022] Open
Abstract
Behaviors are the integrative outcomes of the nervous system, which senses and responds to the internal physiological status and external stimuli. Teleosts are aquatic organisms which are more easily affected by the surrounding environment compared to terrestrial animals. To date, behavioral tests have been widely used to assess potential environmental risks using fish as model animals. In this review, we summarized recent studies regarding the effects of internal and external stimuli on fish behaviors. We concluded that behaviors reflect environmental and physiological changes, which have possible implications for environmental and physiological assessments.
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Affiliation(s)
- Chih-Wei Fu
- Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - Jiun-Lin Horng
- Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Ming-Yi Chou
- Department of Life Science, National Taiwan University, Taipei, Taiwan
- *Correspondence: Ming-Yi Chou,
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7
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Amorim PF, Costa WJEM. Evolution and biogeography of
Anablepsoides
killifishes shaped by Neotropical geological events (Cyprinodontiformes, Aplocheilidae). ZOOL SCR 2022. [DOI: 10.1111/zsc.12539] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Pedro F. Amorim
- Laboratory of Systematics and Evolution of Teleost Fishes Institute of Biology Federal University of Rio de Janeiro Rio de Janeiro Brazil
| | - Wilson J. E. M. Costa
- Laboratory of Systematics and Evolution of Teleost Fishes Institute of Biology Federal University of Rio de Janeiro Rio de Janeiro Brazil
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8
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Liu ST, Horng JL, Lin LY. Role of the Basolateral Na+/H+ Exchanger-2 (NHE2) in Ionocytes of Seawater- Acclimated Medaka (Oryzias latipes). Front Physiol 2022; 13:870967. [PMID: 35399277 PMCID: PMC8987715 DOI: 10.3389/fphys.2022.870967] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 02/28/2022] [Indexed: 12/03/2022] Open
Abstract
Ionocytes in the skin and gills of seawater (SW) fishes are responsible for acid-base regulation and salt secretion. Na+/H+ exchangers (NHEs) are considered the major acid (H+)-secreting transporters in ionocytes of SW fishes. However, the subcellular localization and function of a specific NHE isoform (NHE2) have never clearly been revealed. In this study, we cloned and sequenced NHE2 from an SW-acclimated medaka (Oryzias latipes) and examined its functions in medaka embryos. A phylogenetic analysis showed that the evolutionary relationships of mammalian NHE2 and NHE4 are close to those of fish NHE2. A gene structure analysis showed that tetrapod NHE4 might be a tandem duplication of fish NHE2. Immunohistochemistry with a medaka-specific antibody localized NHE2 to the basolateral membrane of ionocytes. Lost-of-function experiments with photo-activated morpholino oligonucleotides showed that both H+ and Cl– secretion by ionocytes were suppressed in NHE2-knockdown embryos, suggesting that the basolateral NHE2 facilitates acid and salt secretion by ionocytes of medaka in seawater.
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Affiliation(s)
- Sian-Tai Liu
- Department of Life Science, School of Life Sciences, National Taiwan Normal University, Taipei City, Taiwan
| | - Jiun-Lin Horng
- Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei City, Taiwan
| | - Li-Yih Lin
- Department of Life Science, School of Life Sciences, National Taiwan Normal University, Taipei City, Taiwan
- *Correspondence: Li-Yih Lin,
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9
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Amorim PF, Katz AM, Ottoni FP, de Bragança PHN. Genetic Structure of the Mangrove Killifish Kryptolebias hermaphroditus Costa, 2011 (Cyprinodontiformes: Aplocheiloidei) Supports A Wide Connection among its Populations. Zool Stud 2022; 60:e4. [PMID: 35774256 PMCID: PMC9168499 DOI: 10.6620/zs.2022.61-04] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Accepted: 12/19/2021] [Indexed: 06/15/2023]
Abstract
The Kryptolebias marmoratus species group is composed of the only three vertebrate species that lack females. These species present only males and simultaneously hermaphroditic individuals; that are able to reproduce by allogamy, with males, or by autogamy, performing self-fertilization and generating clones of themselves. The proportion of males is variable among those species and even among their populations. Kryptolebias hermaphroditus has the smallest proportion of males. Indeed, no males have been recorded in most known populations. This is a mainly autogamous species, with small populations having a disjunct distribution along the eastern and northern coast of Brazil. Species presenting such adaptations would be expected to have an elevated rate of genetic population structure, reflecting any barriers that obstruct gene flow between populations. Partial sequences of the mitochondrial cytochrome c oxidase I (COI) gene from 335 individuals were sampled to perform a population analysis. Only a single haplotype of COI, widely distributed throughout all the sampled populations, was recovered for K. hermaphroditus. Here we hypothesize that the high degree of communication within populations is probably the main biological feature leading to this pattern.
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Affiliation(s)
- Pedro F Amorim
- Laboratory of Systematics and Evolution of Teleost Fishes, Genetic Graduation Program, Institute of Biology, Federal University of Rio de Janeiro, CEP 21941-902, Rio de Janeiro, Brazil. E-mail: (Amorim)
| | - Axel Makay Katz
- Laboratory of Systematics and Evolution of Teleost Fishes, Biodiversity and Evolutionary Biology Graduation Program, Institute of Biology, Federal University of Rio de Janeiro, CEP 21941-902, Rio de Janeiro, Brazil. E-mail: (Katz)
| | - Felipe Polivanov Ottoni
- Laboratory of Systematics and Ecology of Aquatic Organisms, Center for Agricultural and Environmental Sciences, Federal University of Maranhão, CEP 65500-000, BR-222, KM 04, Boa Vista, Chapadinha, MA, Brasil. E-mail: (Ottoni)
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10
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Marina G, Glover CN, Goss GG, Zimmer AM. The skin of adult rainbow trout is not a significant site of ammonia clearance from the blood. JOURNAL OF FISH BIOLOGY 2021; 99:1529-1534. [PMID: 34159596 DOI: 10.1111/jfb.14831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 05/14/2021] [Accepted: 06/17/2021] [Indexed: 06/13/2023]
Abstract
We hypothesized that the skin acts as an extrabranchial route for ammonia excretion in adult rainbow trout (Oncorhynchus mykiss) following high environmental ammonia (HEA) exposure. Trunks of control or HEA-exposed trout were perfused with saline containing 0 or 1 mmol l-1 NH4 + . Cutaneous ammonia excretion rates increased 2.5-fold following HEA exposure, however there was no difference in rates between trunks perfused with 0 or 1 mmol l-1 NH4 + . The skin is therefore capable of excreting its own ammonia load, but it does not clear circulating ammonia from the plasma.
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Affiliation(s)
- Giacomin Marina
- Department of Biological Sciences, CW 405, Biological Sciences Bldg, University of Alberta, Edmonton, Alberta, Canada
| | - Chris N Glover
- Department of Biological Sciences, CW 405, Biological Sciences Bldg, University of Alberta, Edmonton, Alberta, Canada
- Faculty of Science and Technology and Athabasca River Basin Research Institute, Athabasca University, Athabasca, Alberta, Canada
| | - Greg G Goss
- Department of Biological Sciences, CW 405, Biological Sciences Bldg, University of Alberta, Edmonton, Alberta, Canada
| | - Alex M Zimmer
- Department of Biological Sciences, CW 405, Biological Sciences Bldg, University of Alberta, Edmonton, Alberta, Canada
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11
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Dong YW, Blanchard TS, Noll A, Vasquez P, Schmitz J, Kelly SP, Wright PA, Whitehead A. Genomic and physiological mechanisms underlying skin plasticity during water to air transition in an amphibious fish. J Exp Biol 2021; 224:jeb235515. [PMID: 33328287 PMCID: PMC7860121 DOI: 10.1242/jeb.235515] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 12/09/2020] [Indexed: 12/24/2022]
Abstract
The terrestrial radiation of vertebrates required changes in skin that resolved the dual demands of maintaining a mechanical and physiological barrier while also facilitating ion and gas transport. Using the amphibious killifish Kryptolebias marmoratus, we found that transcriptional regulation of skin morphogenesis was quickly activated upon air exposure (1 h). Rapid regulation of cell-cell adhesion complexes and pathways that regulate stratum corneum formation was consistent with barrier function and mechanical reinforcement. Unique blood vessel architecture and regulation of angiogenesis likely supported cutaneous respiration. Differences in ionoregulatory transcripts and ionocyte morphology were correlated with differences in salinity acclimation and resilience to air exposure. Evolutionary analyses reinforced the adaptive importance of these mechanisms. We conclude that rapid plasticity of barrier, respiratory and ionoregulatory functions in skin evolved to support the amphibious lifestyle of K. marmoratus; similar processes may have facilitated the terrestrial radiation of other contemporary and ancient fishes.
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Affiliation(s)
- Yun-Wei Dong
- The Key Laboratory of Mariculture, Ministry of Education, Fisheries College, Ocean University of China, Qingdao, People's Republic of China
| | - Tessa S Blanchard
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Angela Noll
- Primate Genetics Laboratory, German Primate Center (DPZ), Leibniz Institute for Primate Research, 37077 Göttingen, Germany
| | - Picasso Vasquez
- Department of Environmental Toxicology, University of California Davis, Davis, CA 95616, USA
| | - Juergen Schmitz
- Institute of Experimental Pathology, Center for Molecular Biology of Inflammation (ZMBE), University of Münster, 48149 Münster, Germany
| | - Scott P Kelly
- Department of Biology, York University, Toronto, ON, Canada, M3J 1P3
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Andrew Whitehead
- Department of Environmental Toxicology, Center for Population Biology, Coastal and Marine Sciences Institute, University of California Davis, Davis, CA 95616, USA
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12
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Zimmer AM, Perry SF. The Rhesus glycoprotein Rhcgb is expendable for ammonia excretion and Na + uptake in zebrafish (Danio rerio). Comp Biochem Physiol A Mol Integr Physiol 2020; 247:110722. [PMID: 32437959 DOI: 10.1016/j.cbpa.2020.110722] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 05/01/2020] [Accepted: 05/01/2020] [Indexed: 11/27/2022]
Abstract
In zebrafish (Danio rerio), the ammonia-transporting Rhesus glycoprotein Rhcgb is implicated in mechanisms of ammonia excretion and Na+ uptake. In particular, Rhcgb is thought to play an important role in maintaining ammonia excretion in response to alkaline conditions and high external ammonia (HEA) exposure, in addition to facilitating Na+ uptake via a functional metabolon with the Na+/H+-exchanger Nhe3b, specifically under low Na+ conditions. In the present study, we hypothesized that CRISPR/Cas9 knockout of rhcgb would reduce ammonia excretion and Na+ uptake capacity, particularly under the conditions listed above that have elicited increases in Rhcgb-mediated ammonia excretion and/or Na+ uptake. Contrary to this hypothesis, however, larval and juvenile rhcgb knockout (KO) mutants showed no reductions in ammonia excretion or Na+ uptake under any of the conditions tested in our study. In fact, under control conditions, rhcgb KO mutants generally displayed an increase in ammonia excretion, potentially due to increased transcript abundance of another rh gene, rhbg. Under alkaline conditions, rhcgb KO mutants were also able to maintain ammonia excretion, similar to wild-type fish, and stimulation of ammonia excretion after HEA exposure also was not affected by rhcgb KO. Surprisingly, ammonia excretion and Na+ uptake were unaffected by rhcgb or nhe3b KO in juvenile zebrafish acclimated to normal (800 μmol/L) or low (10 μmol/L) Na+ conditions. These results demonstrate that Rhcgb is expendable for ammonia excretion and Na+ uptake in zebrafish, highlighting the plasticity and flexibility of these physiological systems in this species.
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Affiliation(s)
- Alex M Zimmer
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada; Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
| | - Steve F Perry
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
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13
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Damsgaard C, Baliga VB, Bates E, Burggren W, McKenzie DJ, Taylor E, Wright PA. Evolutionary and cardio-respiratory physiology of air-breathing and amphibious fishes. Acta Physiol (Oxf) 2020; 228:e13406. [PMID: 31630483 DOI: 10.1111/apha.13406] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 09/28/2019] [Accepted: 10/17/2019] [Indexed: 12/24/2022]
Abstract
Air-breathing and amphibious fishes are essential study organisms to shed insight into the required physiological shifts that supported the full transition from aquatic water-breathing fishes to terrestrial air-breathing tetrapods. While the origin of air-breathing in the evolutionary history of the tetrapods has received considerable focus, much less is known about the evolutionary physiology of air-breathing among fishes. This review summarizes recent advances within the field with specific emphasis on the cardiorespiratory regulation associated with air-breathing and terrestrial excursions, and how respiratory physiology of these living transitional forms are affected by development and personality. Finally, we provide a detailed and re-evaluated model of the evolution of air-breathing among fishes that serves as a framework for addressing new questions on the cardiorespiratory changes associated with it. This review highlights the importance of combining detailed studies on piscine air-breathing model species with comparative multi-species studies, to add an additional dimension to our understanding of the evolutionary physiology of air-breathing in vertebrates.
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Affiliation(s)
| | - Vikram B. Baliga
- Department of Zoology University of British Columbia Vancouver BC Canada
| | - Eric Bates
- Derailleur Interactive Vancouver BC Canada
| | - Warren Burggren
- Department of Biological Sciences University of North Texas Denton TX USA
| | - David J. McKenzie
- UMR Marbec, CNRS, IRD, Ifremer Université Montpellier Montpellier France
| | - Edwin Taylor
- School of Biosciences University of Birmingham Birmingham UK
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14
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Ion uptake pathways in European sea bass Dicentrarchus labrax. Gene 2019; 692:126-137. [DOI: 10.1016/j.gene.2019.01.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 12/12/2018] [Accepted: 01/02/2019] [Indexed: 01/20/2023]
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15
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Martin KE, Ehrman JM, Wilson JM, Wright PA, Currie S. Skin ionocyte remodeling in the amphibious mangrove rivulus fish (Kryptolebias marmoratus
). JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2018; 331:128-138. [DOI: 10.1002/jez.2247] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 10/24/2018] [Accepted: 10/25/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Keri E. Martin
- Department of Biology, Mount Allison University; Sackville New Brunswick Canada
| | - James M. Ehrman
- Department of Biology, Mount Allison University; Sackville New Brunswick Canada
| | - Jonathan M. Wilson
- Department of Biology, Wilfrid Laurier University; Waterloo Ontario Canada
| | - Patricia A. Wright
- Department of Integrative Biology, University of Guelph; Guelph Ontario Canada
| | - Suzanne Currie
- Department of Biology, Mount Allison University; Sackville New Brunswick Canada
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Birk MA, Dymowska AK, Seibel BA. Do squid breathe through their skin? ACTA ACUST UNITED AC 2018; 221:jeb.185553. [PMID: 30111556 DOI: 10.1242/jeb.185553] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 08/07/2018] [Indexed: 01/13/2023]
Abstract
Squid are thought to obtain a large portion of their oxygen via simple diffusion across the skin in addition to uptake at the gills. Although this hypothesis has support from indirect evidence and is widely accepted, no empirical examinations have been conducted to assess the validity of this hypothesis. In this study, we examined cutaneous respiration in two squid species, Doryteuthis pealeii and Lolliguncula brevis, using a divided chamber to physically separate the mantle cavity and gills from the outer mantle surface. We measured oxygen consumption and ammonia excretion rates in the two compartments and found that, at rest, squid only obtain enough oxygen cutaneously to meet the demand of the skin tissue locally (12% of total) and excrete little ammonia across the skin. The majority of oxygen is obtained via the traditional branchial pathway. In light of these findings, we re-examine and discuss the indirect evidence that has supported the cutaneous respiration hypothesis.
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Affiliation(s)
- Matthew A Birk
- College of Marine Science, University of South Florida, Saint Petersburg, FL 33701, USA
| | - Agnieszka K Dymowska
- College of Marine Science, University of South Florida, Saint Petersburg, FL 33701, USA
| | - Brad A Seibel
- College of Marine Science, University of South Florida, Saint Petersburg, FL 33701, USA
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17
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Pelster B, Wood CM. Ionoregulatory and oxidative stress issues associated with the evolution of air-breathing. Acta Histochem 2018; 120:667-679. [PMID: 30177382 DOI: 10.1016/j.acthis.2018.08.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Aquatic areas frequently face hypoxic conditions. In order to get sufficient oxygen to support aerobic metabolism, a number of freshwater fish resort to aerial respiration to supplement gill respiration especially in situations with reduced oxygen availability in the water. In many species a concomitant reduction in gill surface area or in gill perfusion reduces possible loss of aerially acquired oxygen to the water at the gills, but it also compromises the ion regulatory capacity of gill tissue. In consequence, the reduced gill contact area with water requires appropriate compensation to maintain ion and acid-base homeostasis, often with important ramifications for other organs. Associated modifications in the structure and function of the gills themselves, the skin, the gut, the kidney, and the physiology of water exchange and ion-linked acid-base regulation are discussed. In air-breathing fish, the gut may gain particular importance for the uptake of ions. In addition, tissues frequently exposed to environmental air encounter much higher oxygen partial pressures than typically observed in fish tissues. Physostomous fish using the swimbladder for aerial respiration, for example, will encounter aerial oxygen partial pressure at the swimbladder epithelium when frequently gulping air in hypoxic water. Hyperoxic conditions or rapid changes in oxygen partial pressures result in an increase in the production of reactive oxygen species (ROS). Accordingly, in air-breathing fish, strategies of ionoregulation may be greatly modified, and the ROS defense capacity of air-exposed tissues is improved.
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18
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Livingston MD, Bhargav VV, Turko AJ, Wilson JM, Wright PA. Widespread use of emersion and cutaneous ammonia excretion in Aplocheiloid killifishes. Proc Biol Sci 2018; 285:rspb.2018.1496. [PMID: 30111602 DOI: 10.1098/rspb.2018.1496] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 07/17/2018] [Indexed: 11/12/2022] Open
Abstract
The invasion of land required amphibious fishes to evolve new strategies to avoid toxic ammonia accumulation in the absence of water flow over the gills. We investigated amphibious behaviour and nitrogen excretion strategies in six phylogenetically diverse Aplocheiloid killifishes (Anablepsoides hartii, Cynodonichthys hildebrandi, Rivulus cylindraceus, Kryptolebias marmoratus, Fundulopanchax gardneri, and Aplocheilus lineatus) in order to determine if a common strategy evolved. All species voluntarily emersed (left water) over several days, and also in response to environmental stressors (low O2, high temperature). All species were ammoniotelic in water and released gaseous ammonia (NH3 volatilization) during air exposure as the primary route for nitrogen excretion. Metabolic depression, urea synthesis, and/or ammonia accumulation during air exposure were not common strategies used by these species. Immunostaining revealed the presence of ammonia-transporting Rhesus proteins (Rhcg1 and Rhcg2) in the skin of all six species, indicating a shared mechanism for ammonia volatilization. We also found Rhcg in the skin of several other fully aquatic fishes, implying that cutaneous ammonia excretion is not exclusive to amphibious fishes. Overall, our results demonstrate that similar nitrogen excretion strategies while out of water were used by all killifish species tested; possibly the result of shared ancestral amphibious traits, phenotypic convergence, or a combination of both.
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Affiliation(s)
- Michael D Livingston
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Vikram V Bhargav
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Andy J Turko
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Jonathan M Wilson
- Department of Biology, Wilfrid Laurier University, ON, Canada N2 L 3C5
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
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19
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Fehsenfeld S, Wood CM. Section-specific expression of acid-base and ammonia transporters in the kidney tubules of the goldfish Carassius auratus and their responses to feeding. Am J Physiol Renal Physiol 2018; 315:F1565-F1582. [PMID: 30089033 DOI: 10.1152/ajprenal.00510.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In teleost fishes, renal contributions to acid-base and ammonia regulation are often neglected compared with the gills. In goldfish, increased renal acid excretion in response to feeding was indicated by increased urine ammonia and inorganic phosphate concentrations and decreased urine pH. By microdissecting the kidney tubules and performing quantitative real-time PCR and/or immunohistochemistry, we profiled the section-specific expression of glutamate dehydrogenase (GDH), glutamine synthetase (GS), Na+/H+-exchanger 3 (NHE3), carbonic anhydrase II (CAIIa), V-H+-ATPase subunit 1b, Cl-/ HCO3- -exchanger 1 (AE1), Na+/ HCO3- -cotransporter 1 (NBC1), Na+/K+-ATPase subunit 1α, and Rhesus-proteins Rhbg, Rhcg1a, and Rhcg1b. Here, we show for the first time that 1) the proximal tubule appears to be the major site for ammoniagenesis, 2) epithelial transporters are differentially expressed along the renal tubule, and 3) a potential feeding-related "acidic tide" results in the differential regulation of epithelial transporters, resembling the mammalian renal response to a metabolic acidosis. Specifically, GDH and NHE3 mRNAs were upregulated and GS downregulated in the proximal tubule upon feeding, suggesting this section as a major site for ammoniagenesis and acid secretion. The distal tubule may play a major role in renal ammonia secretion, with feeding-induced upregulation of mRNA and protein for apical NHE3, cytoplasmic CAIIa, universal Rhcg1a and apical Rhcg1b, and downregulation of basolateral Rhbg and AE1. Changes in mRNA expression of the Wolffian ducts and bladder suggest supporting roles in fine-tuning urine composition. The present study verifies an important renal contribution to acid-base balance and emphasizes that studies looking at the whole kidney may overlook key section-specific responses.
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Affiliation(s)
- Sandra Fehsenfeld
- University of British Columbia, Department of Zoology , Vancouver , Canada
| | - Chris M Wood
- University of British Columbia, Department of Zoology , Vancouver , Canada
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20
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Cuoghi I, Lazzaretti C, Mandrioli M, Mola L, Pederzoli A. Immunohistochemical analysis of the distribution of molecules involved in ionic and pH regulation in the lancelet Branchiostoma floridae (Hubbs, 1922). Acta Histochem 2018; 120:33-40. [PMID: 29169695 DOI: 10.1016/j.acthis.2017.10.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 09/20/2017] [Accepted: 10/30/2017] [Indexed: 11/28/2022]
Abstract
The aim of present work is to analyse the distribution of carbonic anhydrase II (CAII), cystic fibrosis transmembrane regulator (CFTR), vacuolar-type H+-ATPase (V-H+-ATPase), Na+/K+ ATPase, Na+/H+ exchanger (NHE) and SLC26A6 (solute carrier family 26, member 6), also known as pendrin protein, in the lancelet Branchiostoma floridae in order to go in depth in the evolution of osmoregulation and pH regulation in Chordates. In view of their phylogenetic position, lancelets may indeed provide a critical point of reference for studies on osmoregulation evolution in Chordates. The results of present work demonstrated that, except to Na+/K+ ATPase that is strongly expressed in nephridia only, all the other studied molecules are abundantly present in skin, coelomic epithelium, renal papillae and nephridia and hepatic coecum. Thus, it is possible to hypothesize that also in lancelet, as in fish, these organs are involved in pH control and ionic regulation. In the digestive tract of B. floridae, the intestine epithelium was weakly immune-reactive to all tested antibodies, while the hepatic coecum showed an intense immunoreactivity to all molecules. Since in amphioxus the hepatic coecum functions simultaneously as stomach, liver and pancreas, these immunohistochemical results proved the secretion of H+ and HCO3- ions, typical of digestive process. Colocalization studies indicated a co-expression of the studied proteins in all considered organs, excluding NHE and pendrin for renal papillae, since some renal papillae are NHE immunopositive only.
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Affiliation(s)
- Ivan Cuoghi
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 213/D, I-41125 Modena, Italy
| | - Clara Lazzaretti
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 213/D, I-41125 Modena, Italy
| | - Mauro Mandrioli
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 213/D, I-41125 Modena, Italy
| | - Lucrezia Mola
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 213/D, I-41125 Modena, Italy.
| | - Aurora Pederzoli
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 213/D, I-41125 Modena, Italy
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21
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Chen XL, Zhang B, Chng YR, Ong JLY, Chew SF, Wong WP, Lam SH, Ip YK. Na +/H + Exchanger 3 Is Expressed in Two Distinct Types of Ionocyte, and Probably Augments Ammonia Excretion in One of Them, in the Gills of the Climbing Perch Exposed to Seawater. Front Physiol 2017; 8:880. [PMID: 29209224 PMCID: PMC5701670 DOI: 10.3389/fphys.2017.00880] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 10/18/2017] [Indexed: 01/22/2023] Open
Abstract
The freshwater climbing perch, Anabas testudineus, is an euryhaline teleost and an obligate air-breather with the ability to actively excrete ammonia. Members of the Na+/H+ exchanger (NHE) family help maintain intracellular pH homeostasis and ionic balance through the electroneutral exchange of Na+ and H+. This study aimed to obtain, from the gills of A. testudineus, the full cDNA coding sequence of nhe3, and to determine the effects of exposure to seawater or 100 mmol l-1 of NH4Cl in fresh water on its mRNA and protein expression levels. Efforts were also made to elucidate the type of ionocyte that Nhe3 was associated with in the branchial epithelium of A. testudineus. The transcript level and protein abundance of nhe3/Nhe3 were very low in the gills of freshwater A. testudineus, but they increased significantly in the gills of fish acclimated to seawater. In the gills of fish exposed to seawater, Nhe3 was expressed in two distinct types of seawater-inducible Na+/K+-ATPase (Nka)-immunoreactive ionocytes. In Nkaα1b-immunoreactive ionocytes, Nhe3 had an apical localization. As these ionocytes also expressed apical Rhcg1 and basolateral Rhcg2, which are known to transport ammonia, they probably participated in proton-facilitated ammonia excretion in A. testudineus during seawater acclimation. In Nkaα1c-immunoreactive ionocytes, Nhe3 was atypically expressed in the basolateral membrane, and its physiological function is uncertain. For A. testudineus exposed to NH4Cl in fresh water, the transcript and protein expression levels of nhe3/Nhe3 remained low. In conclusion, the branchial Nhe3 of A. testudineus plays a greater physiological role in passive ammonia transport and acid-base balance during seawater acclimation than in active ammonia excretion during environmental ammonia exposure.
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Affiliation(s)
- Xiu L. Chen
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Biyan Zhang
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - You R. Chng
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Jasmine L. Y. Ong
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Shit F. Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore, Singapore
| | - Wai P. Wong
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Siew H. Lam
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
- NUS Environmental Research Institute, National University of Singapore, Singapore, Singapore
| | - Yuen K. Ip
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
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22
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Heffell Q, Turko AJ, Wright PA. Plasticity of skin water permeability and skin thickness in the amphibious mangrove rivulus Kryptolebias marmoratus. J Comp Physiol B 2017; 188:305-314. [PMID: 28940028 DOI: 10.1007/s00360-017-1123-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 08/29/2017] [Accepted: 09/11/2017] [Indexed: 01/29/2023]
Abstract
The skin of amphibious fishes is a multipurpose organ, important for gas and ion exchange and nitrogen excretion when fish are out of water (emersed). We tested the hypothesis that skin permeability is altered to maintain water balance through changes in water permeability and skin thickness during salinity acclimation and/or when fish emerse, using the euryhaline, amphibious fish Kryptolebias marmoratus as a model. We first recorded the behaviour of fish out of water to determine which part of the cutaneous surface was in contact with the substrate. Fish spent about 70% of their time on their ventral surface when out of water. Osmotic permeability of the skin was assessed in fish acclimated to 0.3 or 45‰ using 3H2O fluxes in an in vitro micro-Ussing chamber setup. In freshwater-acclimated fish, 3H2O influx across the skin was significantly higher compared to hypersaline-acclimated fish, with no significant changes in efflux. Prolonged emersion (7 days) resulted in an increase in skin 3H2O influx, but not efflux in fish acclimated to a moist 45‰ substrate. In a separate experiment, dorsal epidermal skin thickness increased while the ventral dermis thickness decreased in fish emersed for over a week. However, there was no link between regional skin thickness and water flux in our experiments. Taken together, these findings suggest that K. marmoratus alter skin permeability to maximize water uptake while emersed in hypersaline conditions, adjustments that probably help them survive months of emersion during the dry season when drinking to replace water loss is not possible.
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Affiliation(s)
- Quentin Heffell
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Andy J Turko
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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23
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Wright PA, Turko AJ. Amphibious fishes: evolution and phenotypic plasticity. ACTA ACUST UNITED AC 2017; 219:2245-59. [PMID: 27489213 DOI: 10.1242/jeb.126649] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Accepted: 06/29/2016] [Indexed: 12/25/2022]
Abstract
Amphibious fishes spend part of their life in terrestrial habitats. The ability to tolerate life on land has evolved independently many times, with more than 200 extant species of amphibious fishes spanning 17 orders now reported. Many adaptations for life out of water have been described in the literature, and adaptive phenotypic plasticity may play an equally important role in promoting favourable matches between the terrestrial habitat and behavioural, physiological, biochemical and morphological characteristics. Amphibious fishes living at the interface of two very different environments must respond to issues relating to buoyancy/gravity, hydration/desiccation, low/high O2 availability, low/high CO2 accumulation and high/low NH3 solubility each time they traverse the air-water interface. Here, we review the literature for examples of plastic traits associated with the response to each of these challenges. Because there is evidence that phenotypic plasticity can facilitate the evolution of fixed traits in general, we summarize the types of investigations needed to more fully determine whether plasticity in extant amphibious fishes can provide indications of the strategies used during the evolution of terrestriality in tetrapods.
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Affiliation(s)
- Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Andy J Turko
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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24
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Allmon EB, Esbaugh AJ. Carbon dioxide induced plasticity of branchial acid-base pathways in an estuarine teleost. Sci Rep 2017; 7:45680. [PMID: 28378831 PMCID: PMC5381225 DOI: 10.1038/srep45680] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 03/02/2017] [Indexed: 12/21/2022] Open
Abstract
Anthropogenic CO2 is expected to drive ocean pCO2 above 1,000 μatm by 2100 – inducing respiratory acidosis in fish that must be corrected through branchial ion transport. This study examined the time course and plasticity of branchial metabolic compensation in response to varying levels of CO2 in an estuarine fish, the red drum, which regularly encounters elevated CO2 and may therefore have intrinsic resilience. Under control conditions fish exhibited net base excretion; however, CO2 exposure resulted in a dose dependent increase in acid excretion during the initial 2 h. This returned to baseline levels during the second 2 h interval for exposures up to 5,000 μatm, but remained elevated for exposures above 15,000 μatm. Plasticity was assessed via gene expression in three CO2 treatments: environmentally realistic 1,000 and 6,000 μatm exposures, and a proof-of-principle 30,000 μatm exposure. Few differences were observed at 1,000 or 6,000 μatm; however, 30,000 μatm stimulated widespread up-regulation. Translocation of V-type ATPase after 1 h of exposure to 30,000 μatm was also assessed; however, no evidence of translocation was found. These results indicate that red drum can quickly compensate to environmentally relevant acid-base disturbances using baseline cellular machinery, yet are capable of plasticity in response to extreme acid-base challenges.
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Affiliation(s)
- Elizabeth B Allmon
- University of Texas at Austin, University of Texas Marine Science Institute, Port Aransas, TX 78373, USA
| | - Andrew J Esbaugh
- University of Texas at Austin, University of Texas Marine Science Institute, Port Aransas, TX 78373, USA
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25
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Blair S, Wilkie M, Edwards S. Rh glycoprotein immunoreactivity in the skin and its role in extrabranchial ammonia excretion by the sea lamprey (Petromyzon marinus) in fresh water. CAN J ZOOL 2017. [DOI: 10.1139/cjz-2016-0120] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aquatic organisms employ various strategies to excrete ammonia across the gills, skin, and (or) renal routes. During three different stages of their life cycle, we hypothesized that the basal vertebrate sea lamprey (Petromyzon marinus L., 1758) used the skin as a route for ammonia excretion. Measurements of ammonia excretion using divided flux chambers revealed that extrabranchial sites (skin plus renal) of ammonia excretion were quantitatively more important in larval sea lampreys, but following metamorphosis, the gills became the dominant route of excretion in juvenile sea lampreys. Despite the greater relative importance of the skin in the larval stage, Rh glycoprotein isoforms Rhbg, Rhcg1, and Rhcg2 were detected in the skin in all three sea lamprey life stages examined, but the patterns of expression were dependent on the life stage. We conclude that, during the relatively sedentary filter-feeding larval stage, extrabranchial routes play an equally important role as the gill in facilitating ammonia excretion. However, the gills by virtue of their extensive branchial vasculature become the dominant route of ammonia excretion following metamorphosis because of the need to offload greater amounts of ammonia arising from higher rates of basal ammonia production and the potential to excrete higher amounts of ammonia following ingestion of protein-rich blood in the parasitic stage.
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Affiliation(s)
- S.D. Blair
- Department of Biology, Appalachian State University, Boone, NC 28608, USA
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - M.P. Wilkie
- Department of Biology, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada
- Department of Biology, Mount Allison University, Sackville, NB E4L 1G7, Canada
| | - S.L. Edwards
- Department of Biology, Appalachian State University, Boone, NC 28608, USA
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26
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Wright PA, Wood CM, Hiroi J, Wilson JM. (Uncommon) Mechanisms of Branchial Ammonia Excretion in the Common Carp (Cyprinus carpio) in Response to Environmentally Induced Metabolic Acidosis. Physiol Biochem Zool 2016; 89:26-40. [PMID: 27082522 DOI: 10.1086/683990] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Freshwater fishes generally increase ammonia excretion in acidic waters. The new model of ammonia transport in freshwater fish involves an association between the Rhesus (Rh) protein Rhcg-b, the Na(+)/H(+) exchanger (NHE), and a suite of other membrane transporters. We tested the hypothesis that Rhcg-b and NHE3 together play a critical role in branchial ammonia excretion in common carp (Cyprinus carpio) chronically exposed to a low-pH environment. Carp were exposed to three sequential environmental treatments-control pH 7.6 water (24 h), pH 4.0 water (72 h), and recovery pH 7.6 water (24 h)-or in a separate series were simply exposed to either control (72 h) or pH 4.0 (72 h) water. Branchial ammonia excretion was increased by ∼2.5-fold in the acid compared with the control period, despite the absence of an increase in the plasma-to-water partial pressure NH3 gradient. Alanine aminotransferase activity was higher in the gills of fish exposed to pH 4 versus control water, suggesting that ammonia may be generated in gill tissue. Gill Rhcg-b and NHE3b messenger RNA levels were significantly elevated in acid-treated relative to control fish, but at the protein level Rhcg-b decreased (30%) and NHE3b increased (2-fold) in response to water of pH 4.0. Using immunofluorescence microscopy, NHE3b and Rhcg-b were found to be colocalized to ionocytes along the interlamellar space of the filament of control fish. After 72 h of acid exposure, Rhcg-b staining almost disappeared from this region, and NHE3b was more prominent along the lamellae. We propose that ammoniagenesis within the gill tissue itself is responsible for the higher rates of branchial ammonia excretion during chronic metabolic acidosis. Unexpectedly, gill Rhcg-b does not appear to be important in gill ammonia transport in low-pH water, but the strong induction of NHE3b suggests that some NH4(+) may be eliminated directly in exchange for Na(+). These findings contrast with previous studies in larval zebrafish (Danio rerio) and medaka (Oryzias latipes), underlining the importance of species comparisons.
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27
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Liu ST, Horng JL, Chen PY, Hwang PP, Lin LY. Salt secretion is linked to acid-base regulation of ionocytes in seawater-acclimated medaka: new insights into the salt-secreting mechanism. Sci Rep 2016; 6:31433. [PMID: 27511107 PMCID: PMC4980601 DOI: 10.1038/srep31433] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 07/12/2016] [Indexed: 11/25/2022] Open
Abstract
Ionocytes in the skin and gills of seawater (SW) teleosts are responsible for both salt and acid secretion. However, the mechanism through which ionocytes secrete acid is still unclear. Here, we hypothesized that apical Na+/H+ exchangers (NHE2/3), carbonic anhydrase (CA2-like), and basolateral HCO3−/Cl− exchanger (AE1) are involved in acid secretion. In addition, the hypothesized involvement of basolateral AE1 suggested that acid secretion may be linked to Cl− secretion by ionocytes. The scanning ion-selective electrode technique (SIET) was used to measure H+ and Cl− secretion by ionocytes in the skin of medaka larvae acclimated to SW. Treatment with inhibitors of NHE, CA, and AE suppressed both H+ and Cl− secretion by ionocytes. Short-term exposure to hypercapnic SW stimulated both H+ and Cl− secretion. mRNA of CA2-like and AE1 were localized to ionocytes in the skin. Branchial mRNA levels of NKCC1a, CA2-like, and AE1a increased together with the salinity to which fish were acclimated. In addition, both AE1a and AE1b mRNA increased in fish acclimated to acidified (pH 7) SW; NKCC1a mRNA increased in fish acclimated to pH 9 SW. This study reveals the mechanism of H+ secretion by ionocytes, and refines our understanding of the well-established mechanism of Cl− secretion by ionocytes of SW fish.
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Affiliation(s)
- Sian-Tai Liu
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Jiun-Lin Horng
- Department of Anatomy and Cell Biology, Taipei Medical University, Taipei, Taiwan
| | - Po-Yen Chen
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Li-Yih Lin
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
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28
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Turko AJ, Wright PA. Evolution, ecology and physiology of amphibious killifishes (Cyprinodontiformes). JOURNAL OF FISH BIOLOGY 2015; 87:815-835. [PMID: 26299792 DOI: 10.1111/jfb.12758] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 06/24/2015] [Indexed: 06/04/2023]
Abstract
The order Cyprinodontiformes contains an exceptional diversity of amphibious taxa, including at least 34 species from six families. These cyprinodontiforms often inhabit intertidal or ephemeral habitats characterized by low dissolved oxygen or otherwise poor water quality, conditions that have been hypothesized to drive the evolution of terrestriality. Most of the amphibious species are found in the Rivulidae, Nothobranchiidae and Fundulidae. It is currently unclear whether the pattern of amphibiousness observed in the Cyprinodontiformes is the result of repeated, independent evolutions, or stems from an amphibious common ancestor. Amphibious cyprinodontiforms leave water for a variety of reasons: some species emerse only briefly, to escape predation or capture prey, while others occupy ephemeral habitats by living for months at a time out of water. Fishes able to tolerate months of emersion must maintain respiratory gas exchange, nitrogen excretion and water and salt balance, but to date knowledge of the mechanisms that facilitate homeostasis on land is largely restricted to model species. This review synthesizes the available literature describing amphibious lifestyles in cyprinodontiforms, compares the behavioural and physiological strategies used to exploit the terrestrial environment and suggests directions and ideas for future research.
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Affiliation(s)
- A J Turko
- Department of Integrative Biology, University of Guelph, 488 Gordon Street, Guelph, ON, N1G 2W1, Canada
| | - P A Wright
- Department of Integrative Biology, University of Guelph, 488 Gordon Street, Guelph, ON, N1G 2W1, Canada
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Lawrence MJ, Wright PA, Wood CM. Physiological and molecular responses of the goldfish (Carassius auratus) kidney to metabolic acidosis, and potential mechanisms of renal ammonia transport. ACTA ACUST UNITED AC 2015; 218:2124-35. [PMID: 25987732 DOI: 10.1242/jeb.117689] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 05/05/2015] [Indexed: 01/20/2023]
Abstract
Relative to the gills, the mechanisms by which the kidney contributes to ammonia and acid-base homeostasis in fish are poorly understood. Goldfish were exposed to a low pH environment (pH 4.0, 48 h), which induced a characteristic metabolic acidosis and an increase in total plasma [ammonia] but reduced plasma ammonia partial pressure (PNH3). In the kidney tissue, total ammonia, lactate and intracellular pH remained unchanged. The urinary excretion rate of net base under control conditions changed to net acid excretion under low pH, with contributions from both the NH4 (+) (∼30%) and titratable acidity minus bicarbonate (∼70%; TA-HCO3 (-)) components. Inorganic phosphate (Pi), urea and Na(+) excretion rates were also elevated while Cl(-) excretion rates were unchanged. Renal alanine aminotransferase activity increased under acidosis. The increase in renal ammonia excretion was due to significant increases in both the glomerular filtration and the tubular secretion rates of ammonia, with the latter accounting for ∼75% of the increase. There was also a 3.5-fold increase in the mRNA expression of renal Rhcg-b (Rhcg1) mRNA. There was no relationship between ammonia secretion and Na(+) reabsorption. These data indicate that increased renal ammonia secretion during acidosis is probably mediated through Rhesus (Rh) glycoproteins and occurs independently of Na(+) transport, in contrast to branchial and epidermal models of Na(+)-dependent ammonia transport in freshwater fish. Rather, we propose a model of parallel H(+)/NH3 transport as the primary mechanism of renal tubular ammonia secretion that is dependent on renal amino acid catabolism.
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Affiliation(s)
- Michael J Lawrence
- Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1 Department of Biology, Carleton University, Ottawa, ON, Canada K1S 5B6
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Chris M Wood
- Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1 Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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Zimmer AM, Brauner CJ, Wood CM. Ammonia transport across the skin of adult rainbow trout (Oncorhynchus mykiss) exposed to high environmental ammonia (HEA). J Comp Physiol B 2013; 184:77-90. [PMID: 24114656 DOI: 10.1007/s00360-013-0784-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 09/04/2013] [Accepted: 09/23/2013] [Indexed: 12/27/2022]
Abstract
Recent molecular evidence points towards a capacity for ammonia transport across the skin of adult rainbow trout. A series of in vivo and in vitro experiments were conducted to understand the role of cutaneous ammonia excretion (J amm) under control conditions and after 12-h pre-exposure to high environmental ammonia (HEA; 2 mmol/l NH4HCO3). Divided chamber experiments with bladder-catheterized, rectally ligated fish under light anesthesia were performed to separate cutaneous J amm from branchial, renal, and intestinal J amm. Under control conditions, cutaneous J amm accounted for 4.5 % of total J amm in vivo. In fish pre-exposed to HEA, plasma total ammonia concentration increased 20-fold to approximately 1,000 μmol/l, branchial J amm increased 1.5- to 2.7-fold, and urinary J amm increased about 7-fold. Urinary J amm still accounted for less than 2 % of total J amm. Cutaneous J amm increased 4-fold yet amounted to only 5.7 % of total J amm in these fish. Genes (Rhcg1, Rhcg2, Rhbg, NHE-2, v-type H(+)-ATPase) known to be involved in ammonia excretion at the gills of trout were all expressed at the mRNA level in the skin, but their expression did not increase with HEA pre-exposure. In vitro analyses using [(14)C] methylamine (MA), an ammonia analog which is transported by Rh proteins, demonstrated that MA permeability in isolated skin sections was higher in HEA pre-exposed fish than in control fish. The addition of basolateral ammonia (1,000 μmol/l) to this system abolished this increase in permeability, suggesting ammonia competition with MA for Rh-mediated transport across the skin of HEA pre-exposed trout; this did not occur in skin sections from control trout. Moreover, in vitro J amm by the skin of fish which had been pre-exposed to HEA was also higher than in control fish in the absence of basolateral ammonia, pointing towards a possible cutaneous ammonia loading in response to HEA. In vitro MA permeability was reduced upon the addition of amiloride (10(-4) mol/l), but not phenamil (10(-5) mol/l) suggesting a role for a Na/H-exchanger (NHE) in cutaneous ammonia transport, as has been previously described in the skin of larval fish. Overall, it appears that under control conditions and in response to HEA pre-exposure, the skin makes only a very minor contribution to total J amm, but the observed increases in cutaneous J amm in vivo and in cutaneous J amm and MA permeability in vitro demonstrate the capacity for ammonia transport in the skin of adult trout. It remains unclear if this capacity may become significant under certain environmental challenges or if it is merely a remnant of cutaneous transport capacity from early life stages in these fish.
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Affiliation(s)
- Alex M Zimmer
- Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada,
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