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Verhille CE, MacDonald M, Noble B, Demorest G, Roche A, Frazier K, Albertson LK. Thermal tolerance of giant salmonfly nymphs ( Pteronarcys californica) varies across populations in a regulated river. CONSERVATION PHYSIOLOGY 2024; 12:coae043. [PMID: 38974500 PMCID: PMC11225080 DOI: 10.1093/conphys/coae043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 05/24/2024] [Accepted: 06/10/2024] [Indexed: 07/09/2024]
Abstract
Warming of aquatic ecosystems is transforming the distribution, phenology and growth of the organisms dependent upon these ecosystems. Aquatic insects such as stoneflies are especially vulnerable to warming because the aquatic nymph stage of their life cycle depends on cool, well-oxygenated, flowing water habitat. We tracked thermal effects on available aerobic capacity of the aquatic nymph stage of an iconic and vulnerable stonefly species, the giant salmonfly (Pteronarcys californica), to compare habitat thermal regime measurements for two salmonfly populations from habitats separated by a gradient in summer weekly maximum temperatures. Contrary to expectations, the thermal optima range of the warmer habitat population was cooler than for the cooler habitat population. We posit that this unexpected interpopulation variation in thermal response is more strongly driven by diel and seasonal thermal variability than by the highest summer temperatures experienced within respective habitats. Additionally, we show that summer daily maximum temperatures could result in periodic limits in available aerobic capacity to support work of the warmer habitat nymphs and may be the mechanism underlying reduced abundance relative to the upstream cooler habitat population. Our findings provide insight into potential thermal and metabolic mechanisms that could regulate the success of ecological and culturally important aquatic insect species experiencing global change. We conclude that thermal regimes and thermal variation, not just mean and maximum temperatures, are critical drivers of aquatic insect responses to water temperatures.
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Affiliation(s)
| | - Michael MacDonald
- Department of Ecology, Montana State University, Bozeman, MT 59717, USA
| | - Ben Noble
- Department of Ecology, Montana State University, Bozeman, MT 59717, USA
| | - Gavin Demorest
- Department of Ecology, Montana State University, Bozeman, MT 59717, USA
| | - Alzada Roche
- Department of Ecology, Montana State University, Bozeman, MT 59717, USA
| | - Kayleigh Frazier
- Department of Ecology, Montana State University, Bozeman, MT 59717, USA
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De Padova J, Anderson NK, Halbauer R, Preininger D, Fuxjager MJ. Acute hypoxia exposure rapidly triggers behavioral changes linked to cutaneous gas exchange in Lake Titicaca frogs. Behav Processes 2024; 219:105047. [PMID: 38762053 DOI: 10.1016/j.beproc.2024.105047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 03/07/2024] [Accepted: 05/14/2024] [Indexed: 05/20/2024]
Abstract
Ventilation is critical to animal life-it ensures that individuals move air/water across their respiratory surface, and thus it sustains gas exchange with the environment. Many species have evolved highly specialized (if not unusual) ventilatory mechanisms, including the use of behavior to facilitate different aspects of breathing. However, these behavioral traits are often only described anecdotally, and the ecological conditions that elicit them are typically unclear. We study one such "ventilation behavior" in Lake Titicaca frogs (Telmatobius culeus). These frogs inhabit high-altitude (i.e., low oxygen) lakes in the Andean Mountains of South America, and they have become textbook examples of cutaneous gas exchange, which is essentially breathing that occurs across the skin. Accordingly, this species has evolved large, baggy skin-folds that dangle from the body to increase the surface area for ventilation. We show that individuals exposed to acute hypoxic conditions that mirror what free-living individuals likely encounter quickly (within minutes) decrease their activity levels, and thus become very still. If oxygen levels continue to decline, the frogs soon begin to perform push-up behaviors that presumably break the low-oxygen boundary layer around skin-folds to increase the conductance of the water/skin gas exchange pathway. Altogether, we suspect that individuals rapidly adjust aspects of their behavior in response to seemingly sudden changes to the oxygen environment as a mechanism to fine tune cutaneous respiration.
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Affiliation(s)
- Jordan De Padova
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, RI 02912, USA
| | - Nigel K Anderson
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, RI 02912, USA
| | | | - Doris Preininger
- Vienna Zoo, Vienna, Austria; Department of Evolutionary Biology, University of Vienna, Austria
| | - Matthew J Fuxjager
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, RI 02912, USA.
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Birrell JH, Woods HA. Going with the flow - how a stream insect, Pteronarcys californica, exploits local flows to increase oxygen availability. J Exp Biol 2023; 226:286586. [PMID: 36633213 DOI: 10.1242/jeb.244609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 01/09/2023] [Indexed: 01/13/2023]
Abstract
For insects, life in water is challenging because oxygen supply is typically low compared with in air. Oxygen limitation may occur when oxygen levels or water flows are low or when warm temperatures stimulate metabolic demand for oxygen. A potential mechanism for mitigating oxygen shortages is behavior - moving to cooler, more oxygenated or faster flowing microhabitats. Whether stream insects can make meaningful choices, however, depends on: (i) how temperature, oxygen and flow vary at microspatial scales and (ii) the ability of insects to sense and exploit that variation. To assess the extent of microspatial variation in conditions, we measured temperature, oxygen saturation and flow velocity within riffles of two streams in Montana, USA. In the lab, we then examined preferences of nymphs of the stonefly Pteronarcys californica to experimental gradients based on field-measured values. Temperature and oxygen level varied only slightly within stream riffles. By contrast, flow velocity was highly heterogeneous, often varying by more than 125 cm s-1 within riffles and 44 cm s-1 around individual cobbles. Exploiting micro-variation in flow may thus be the most reliable option for altering rates of oxygen transport. In support of this prediction, P. californica showed little ability to exploit gradients in temperature and oxygen but readily exploited micro-variation in flow - consistently choosing higher flows when conditions were warm or hypoxic. These behaviors may help stream insects mitigate low-oxygen stress from climate change and other anthropogenic disturbances.
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Affiliation(s)
- Jackson H Birrell
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - H Arthur Woods
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
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Harvey JA, Tougeron K, Gols R, Heinen R, Abarca M, Abram PK, Basset Y, Berg M, Boggs C, Brodeur J, Cardoso P, de Boer JG, De Snoo GR, Deacon C, Dell JE, Desneux N, Dillon ME, Duffy GA, Dyer LA, Ellers J, Espíndola A, Fordyce J, Forister ML, Fukushima C, Gage MJG, García‐Robledo C, Gely C, Gobbi M, Hallmann C, Hance T, Harte J, Hochkirch A, Hof C, Hoffmann AA, Kingsolver JG, Lamarre GPA, Laurance WF, Lavandero B, Leather SR, Lehmann P, Le Lann C, López‐Uribe MM, Ma C, Ma G, Moiroux J, Monticelli L, Nice C, Ode PJ, Pincebourde S, Ripple WJ, Rowe M, Samways MJ, Sentis A, Shah AA, Stork N, Terblanche JS, Thakur MP, Thomas MB, Tylianakis JM, Van Baaren J, Van de Pol M, Van der Putten WH, Van Dyck H, Verberk WCEP, Wagner DL, Weisser WW, Wetzel WC, Woods HA, Wyckhuys KAG, Chown SL. Scientists' warning on climate change and insects. ECOL MONOGR 2022. [DOI: 10.1002/ecm.1553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jeffrey A. Harvey
- Department of Terrestrial Ecology Netherlands Institute of Ecology (NIOO‐KNAW) Wageningen The Netherlands
- Department of Ecological Sciences Vrije Universiteit Amsterdam Amsterdam The Netherlands
| | - Kévin Tougeron
- Earth and Life Institute, Ecology & Biodiversity Université catholique de Louvain Louvain‐la‐Neuve Belgium
- EDYSAN, UMR 7058, Université de Picardie Jules Verne, CNRS Amiens France
| | - Rieta Gols
- Laboratory of Entomology Wageningen University Wageningen The Netherlands
| | - Robin Heinen
- Department of Life Science Systems, School of Life Sciences Technical University of Munich, Terrestrial Ecology Research Group Freising Germany
| | - Mariana Abarca
- Department of Biological Sciences Smith College Northampton Massachusetts USA
| | - Paul K. Abram
- Agriculture and Agri‐Food Canada, Agassiz Research and Development Centre Agassiz British Columbia Canada
| | - Yves Basset
- Smithsonian Tropical Research Institute Panama City Republic of Panama
- Department of Ecology Institute of Entomology, Czech Academy of Sciences Ceske Budejovice Czech Republic
| | - Matty Berg
- Department of Ecological Sciences Vrije Universiteit Amsterdam Amsterdam The Netherlands
- Groningen Institute of Evolutionary Life Sciences University of Groningen Groningen The Netherlands
| | - Carol Boggs
- School of the Earth, Ocean and Environment and Department of Biological Sciences University of South Carolina Columbia South Carolina USA
- Rocky Mountain Biological Laboratory Gothic Colorado USA
| | - Jacques Brodeur
- Institut de recherche en biologie végétale, Département de sciences biologiques Université de Montréal Montréal Québec Canada
| | - Pedro Cardoso
- Laboratory for Integrative Biodiversity Research (LIBRe), Finnish Museum of Natural History Luomus University of Helsinki Helsinki Finland
| | - Jetske G. de Boer
- Department of Terrestrial Ecology Netherlands Institute of Ecology (NIOO‐KNAW) Wageningen The Netherlands
| | - Geert R. De Snoo
- Department of Terrestrial Ecology Netherlands Institute of Ecology (NIOO‐KNAW) Wageningen The Netherlands
| | - Charl Deacon
- Department of Conservation Ecology and Entomology, Faculty of AgriSciences Stellenbosch University Stellenbosch South Africa
| | - Jane E. Dell
- Geosciences and Natural Resources Department Western Carolina University Cullowhee North Carolina USA
| | | | - Michael E. Dillon
- Department of Zoology and Physiology and Program in Ecology University of Wyoming Laramie Wyoming USA
| | - Grant A. Duffy
- School of Biological Sciences Monash University Melbourne Victoria Australia
- Department of Marine Science University of Otago Dunedin New Zealand
| | - Lee A. Dyer
- University of Nevada Reno – Ecology, Evolution and Conservation Biology Reno Nevada USA
| | - Jacintha Ellers
- Department of Ecological Sciences Vrije Universiteit Amsterdam Amsterdam The Netherlands
| | - Anahí Espíndola
- Department of Entomology University of Maryland College Park Maryland USA
| | - James Fordyce
- Department of Ecology and Evolutionary Biology University of Tennessee, Knoxville Knoxville Tennessee USA
| | - Matthew L. Forister
- University of Nevada Reno – Ecology, Evolution and Conservation Biology Reno Nevada USA
| | - Caroline Fukushima
- Laboratory for Integrative Biodiversity Research (LIBRe), Finnish Museum of Natural History Luomus University of Helsinki Helsinki Finland
| | | | | | - Claire Gely
- Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering James Cook University Cairns Queensland Australia
| | - Mauro Gobbi
- MUSE‐Science Museum, Research and Museum Collections Office Climate and Ecology Unit Trento Italy
| | - Caspar Hallmann
- Radboud Institute for Biological and Environmental Sciences Radboud University Nijmegen The Netherlands
| | - Thierry Hance
- Earth and Life Institute, Ecology & Biodiversity Université catholique de Louvain Louvain‐la‐Neuve Belgium
| | - John Harte
- Energy and Resources Group University of California Berkeley California USA
| | - Axel Hochkirch
- Department of Biogeography Trier University Trier Germany
- IUCN SSC Invertebrate Conservation Committee
| | - Christian Hof
- Department of Life Science Systems, School of Life Sciences Technical University of Munich, Terrestrial Ecology Research Group Freising Germany
| | - Ary A. Hoffmann
- Bio21 Institute, School of BioSciences University of Melbourne Melbourne Victoria Australia
| | - Joel G. Kingsolver
- Department of Biology University of North Carolina Chapel Hill North Carolina USA
| | - Greg P. A. Lamarre
- Smithsonian Tropical Research Institute Panama City Republic of Panama
- Department of Ecology Institute of Entomology, Czech Academy of Sciences Ceske Budejovice Czech Republic
| | - William F. Laurance
- Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering James Cook University Cairns Queensland Australia
| | - Blas Lavandero
- Laboratorio de Control Biológico Universidad de Talca Talca Chile
| | - Simon R. Leather
- Center for Integrated Pest Management Harper Adams University Newport UK
| | - Philipp Lehmann
- Department of Zoology Stockholm University Stockholm Sweden
- Zoological Institute and Museum University of Greifswald Greifswald Germany
| | - Cécile Le Lann
- University of Rennes, CNRS, ECOBIO [(Ecosystèmes, biodiversité, évolution)] ‐ UMR 6553 Rennes France
| | | | - Chun‐Sen Ma
- Climate Change Biology Research Group, State Key Laboratory for Biology of Plant Diseases and Insect Pests Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing China
| | - Gang Ma
- Climate Change Biology Research Group, State Key Laboratory for Biology of Plant Diseases and Insect Pests Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing China
| | | | | | - Chris Nice
- Department of Biology Texas State University San Marcos Texas USA
| | - Paul J. Ode
- Department of Agricultural Biology Colorado State University Fort Collins Colorado USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins Colorado USA
| | - Sylvain Pincebourde
- Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS Université de Tours Tours France
| | - William J. Ripple
- Department of Forest Ecosystems and Society Oregon State University Oregon USA
| | - Melissah Rowe
- Netherlands Institute of Ecology (NIOO‐KNAW) Department of Animal Ecology Wageningen The Netherlands
| | - Michael J. Samways
- Department of Conservation Ecology and Entomology, Faculty of AgriSciences Stellenbosch University Stellenbosch South Africa
| | - Arnaud Sentis
- INRAE, Aix‐Marseille University, UMR RECOVER Aix‐en‐Provence France
| | - Alisha A. Shah
- W.K. Kellogg Biological Station, Department of Integrative Biology Michigan State University East Lansing Michigan USA
| | - Nigel Stork
- Centre for Planetary Health and Food Security, School of Environment and Science Griffith University Nathan Queensland Australia
| | - John S. Terblanche
- Department of Conservation Ecology and Entomology, Faculty of AgriSciences Stellenbosch University Stellenbosch South Africa
| | - Madhav P. Thakur
- Institute of Ecology and Evolution University of Bern Bern Switzerland
| | - Matthew B. Thomas
- York Environmental Sustainability Institute and Department of Biology University of York York UK
| | - Jason M. Tylianakis
- Bioprotection Aotearoa, School of Biological Sciences University of Canterbury Christchurch New Zealand
| | - Joan Van Baaren
- University of Rennes, CNRS, ECOBIO [(Ecosystèmes, biodiversité, évolution)] ‐ UMR 6553 Rennes France
| | - Martijn Van de Pol
- Netherlands Institute of Ecology (NIOO‐KNAW) Department of Animal Ecology Wageningen The Netherlands
- College of Science and Engineering James Cook University Townsville Queensland Australia
| | - Wim H. Van der Putten
- Department of Terrestrial Ecology Netherlands Institute of Ecology (NIOO‐KNAW) Wageningen The Netherlands
| | - Hans Van Dyck
- Earth and Life Institute, Ecology & Biodiversity Université catholique de Louvain Louvain‐la‐Neuve Belgium
| | | | - David L. Wagner
- Ecology and Evolutionary Biology University of Connecticut Storrs Connecticut USA
| | - Wolfgang W. Weisser
- Department of Life Science Systems, School of Life Sciences Technical University of Munich, Terrestrial Ecology Research Group Freising Germany
| | - William C. Wetzel
- Department of Entomology, Department of Integrative Biology, and Ecology, Evolution, and Behavior Program Michigan State University East Lansing Michigan USA
| | - H. Arthur Woods
- Division of Biological Sciences University of Montana Missoula Montana USA
| | - Kris A. G. Wyckhuys
- Chrysalis Consulting Hanoi Vietnam
- China Academy of Agricultural Sciences Beijing China
| | - Steven L. Chown
- Securing Antarctica's Environmental Future, School of Biological Sciences Monash University Melbourne Victoria Australia
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Frakes JI, Malison RL, Sydor MJ, Arthur Woods H. Exposure to copper increases hypoxia sensitivity and decreases upper thermal tolerance of giant salmonfly nymphs (Pteronarcys californica). JOURNAL OF INSECT PHYSIOLOGY 2022; 143:104455. [PMID: 36368599 PMCID: PMC10263297 DOI: 10.1016/j.jinsphys.2022.104455] [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: 06/14/2022] [Revised: 11/03/2022] [Accepted: 11/04/2022] [Indexed: 06/15/2023]
Abstract
Many aquatic insects are exposed to the dual stressors of heavy metal pollution and rising water temperatures from global warming. These stresses may interact and have stronger impacts on aquatic organisms if heavy metals interfere with the ability of these organisms to handle high temperatures. Here we focus on the effect of copper on upper thermal limits of giant salmonfly nymphs (Order: Plecoptera, Pteronarcys californica), a stonefly species which is common in parts of western North America. Experimental exposure to copper reduced upper thermal limits by ∼ 10 °C in some cases and depressed the hypoxia tolerance (Pcrit) of nymphs by ∼ 0.5 mg L-1 DO. These results suggest that copper inhibits the delivery of oxygen, which may explain, in part, the strong reductions in CTMAX that we report. Fluorescence microscopy of Cu-exposed individuals indicated high levels of copper in chloride cells but no clear evidence of damage to or high levels of copper on the gills themselves. Our study indicates that populations of aquatic insects from copper-polluted environments may be further at risk to future warming than those from uncontaminated environments.
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Affiliation(s)
- James I Frakes
- University of Montana, 32 Campus Dr. Missoula, MT 59812, United States.
| | - Rachel L Malison
- Flathead Lake Biological Station, 32125 Bio Station Ln, Polson, MT 59860, United States.
| | - Matthew J Sydor
- University of Montana, 32 Campus Dr. Missoula, MT 59812, United States.
| | - H Arthur Woods
- University of Montana, 32 Campus Dr. Missoula, MT 59812, United States.
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Atkinson D, Leighton G, Berenbrink M. Controversial Roles of Oxygen in Organismal Responses to Climate Warming. THE BIOLOGICAL BULLETIN 2022; 243:207-219. [PMID: 36548977 DOI: 10.1086/722471] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
AbstractDespite the global ecological importance of climate change, controversy surrounds how oxygen affects the fate of aquatic ectotherms under warming. Disagreements extend to the nature of oxygen bioavailability and whether oxygen usually limits growth under warming, explaining smaller adult size. These controversies affect two influential hypotheses: gill oxygen limitation and oxygen- and capacity-limited thermal tolerance. Here, we promote deeper integration of physiological and evolutionary mechanisms. We first clarify the nature of oxygen bioavailability in water, developing a new mass-transfer model that can be adapted to compare warming impacts on organisms with different respiratory systems and flow regimes. By distinguishing aerobic energy costs of moving oxygen from environment to tissues from costs of all other functions, we predict a decline in energy-dependent fitness during hypoxia despite approximately constant total metabolic rate before reaching critically low environmental oxygen. A new measure of oxygen bioavailability that keeps costs of generating water convection constant predicts a higher thermal sensitivity of oxygen uptake in an amphipod model than do previous oxygen supply indices. More importantly, by incorporating size- and temperature-dependent costs of generating water flow, we propose that oxygen limitation at different body sizes and temperatures can be modeled mechanistically. We then report little evidence for oxygen limitation of growth and adult size under benign warming. Yet occasional oxygen limitation, we argue, may, along with other selective pressures, help maintain adaptive plastic responses to warming. Finally, we discuss how to overcome flaws in a commonly used growth model that undermine predictions of warming impacts.
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Woods HA, Moran AL, Atkinson D, Audzijonyte A, Berenbrink M, Borges FO, Burnett KG, Burnett LE, Coates CJ, Collin R, Costa-Paiva EM, Duncan MI, Ern R, Laetz EMJ, Levin LA, Lindmark M, Lucey NM, McCormick LR, Pierson JJ, Rosa R, Roman MR, Sampaio E, Schulte PM, Sperling EA, Walczyńska A, Verberk WCEP. Integrative Approaches to Understanding Organismal Responses to Aquatic Deoxygenation. THE BIOLOGICAL BULLETIN 2022; 243:85-103. [PMID: 36548975 DOI: 10.1086/722899] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
AbstractOxygen bioavailability is declining in aquatic systems worldwide as a result of climate change and other anthropogenic stressors. For aquatic organisms, the consequences are poorly known but are likely to reflect both direct effects of declining oxygen bioavailability and interactions between oxygen and other stressors, including two-warming and acidification-that have received substantial attention in recent decades and that typically accompany oxygen changes. Drawing on the collected papers in this symposium volume ("An Oxygen Perspective on Climate Change"), we outline the causes and consequences of declining oxygen bioavailability. First, we discuss the scope of natural and predicted anthropogenic changes in aquatic oxygen levels. Although modern organisms are the result of long evolutionary histories during which they were exposed to natural oxygen regimes, anthropogenic change is now exposing them to more extreme conditions and novel combinations of low oxygen with other stressors. Second, we identify behavioral and physiological mechanisms that underlie the interactive effects of oxygen with other stressors, and we assess the range of potential organismal responses to oxygen limitation that occur across levels of biological organization and over multiple timescales. We argue that metabolism and energetics provide a powerful and unifying framework for understanding organism-oxygen interactions. Third, we conclude by outlining a set of approaches for maximizing the effectiveness of future work, including focusing on long-term experiments using biologically realistic variation in experimental factors and taking truly cross-disciplinary and integrative approaches to understanding and predicting future effects.
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Malison RL, Frakes JI, Andreas AL, Keller PR, Hamant E, Shah AA, Woods HA. Plasticity of salmonfly (Pteronarcys californica) respiratory phenotypes in response to changes in temperature and oxygen. J Exp Biol 2022; 225:276432. [PMID: 36004671 DOI: 10.1242/jeb.244253] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 08/19/2022] [Indexed: 11/20/2022]
Abstract
Like all taxa, populations of aquatic insects may respond to climate change by evolving new physiologies or behaviors, shifting their ranges, exhibiting physiological and behavioral plasticity, or by going extinct. We evaluated the importance of plasticity by measuring changes in growth, survival, and respiratory phenotypes of salmonfly nymphs (the stonefly Pteronarcys californica) in response to experimental combinations of dissolved oxygen and temperature. Overall, smaller individuals grew more rapidly during the six-week experimental period, and oxygen and temperature interacted to affect growth in complex ways. Survival was lower for the warm treatment, though only four mortalities occurred (91.6 vs 100%). Nymphs acclimated to warmer temperatures did not have higher critical thermal maxima (CTMAX), but those acclimated to hypoxia had CTMAX values (in normoxia) higher by approximately 1 °C. These results suggest possible adaptive plasticity of systems for taking up or delivering oxygen. We examined these possibilities by measuring the oxygen-sensitivity of metabolic rates and the morphologies of tracheal gill tufts located ventrally on thoracic and abdominal segments. Mass-specific metabolic rates of individuals acclimated to warmer temperatures were higher in acute hypoxia but lower in normoxia, regardless of their recent history of oxygen exposure during acclimation. The morphology of gill filaments, however, changed in ways that appeared to depress rates of oxygen delivery in functional hypoxia. Our combined results from multiple performance metrics indicate that rising temperatures and hypoxia may interact to magnify the risks to aquatic insects, but that physiological plasticity in respiratory phenotypes may offset some of these risks.
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Affiliation(s)
- Rachel L Malison
- The University of Montana, Division of Biological Sciences, Flathead Lake Biological Station, 32125 Bio Station Lane, Polson, MT 59801, USA
| | - James I Frakes
- The University of Montana, 32 Campus Drive, Missoula, MT 59812, USA
| | - Amanda L Andreas
- The University of Montana, 32 Campus Drive, Missoula, MT 59812, USA
| | - Priya R Keller
- The University of Montana, 32 Campus Drive, Missoula, MT 59812, USA
| | - Emily Hamant
- The University of Montana, 32 Campus Drive, Missoula, MT 59812, USA
| | - Alisha A Shah
- The University of Montana, 32 Campus Drive, Missoula, MT 59812, USA
| | - H Arthur Woods
- The University of Montana, 32 Campus Drive, Missoula, MT 59812, USA
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