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Lonthair JK, Wegner NC, Cheng BS, Fangue NA, O'Donnell MJ, Regish AM, Swenson JD, Argueta E, McCormick SD, Letcher BH, Komoroske LM. The gill oxygen limitation hypothesis remains unsupported by experimental evidence. Response to 'Testing mechanistic theories must be based on correct interpretations'. J Exp Biol 2024; 227:jeb248173. [PMID: 39193665 DOI: 10.1242/jeb.248173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Accepted: 07/18/2024] [Indexed: 08/29/2024]
Affiliation(s)
- Joshua K Lonthair
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- National Research Council under contract to Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA 92037-1508, USA
| | - Nicholas C Wegner
- Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla 92037-1508, CA, USA
| | - Brian S Cheng
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Nann A Fangue
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA 95616, USA
| | - Matthew J O'Donnell
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Amy M Regish
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - John D Swenson
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Estefany Argueta
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Stephen D McCormick
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Benjamin H Letcher
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Lisa M Komoroske
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
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Lonthair JK, Wegner NC, Cheng BS, Fangue NA, O'Donnell MJ, Regish AM, Swenson JD, Argueta E, McCormick SD, Letcher BH, Komoroske LM. Smaller body size under warming is not due to gill-oxygen limitation in a cold-water salmonid. J Exp Biol 2024; 227:jeb246477. [PMID: 38380449 PMCID: PMC11093110 DOI: 10.1242/jeb.246477] [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: 07/26/2023] [Accepted: 01/10/2024] [Indexed: 02/22/2024]
Abstract
Declining body size in fishes and other aquatic ectotherms associated with anthropogenic climate warming has significant implications for future fisheries yields, stock assessments and aquatic ecosystem stability. One proposed mechanism seeking to explain such body-size reductions, known as the gill oxygen limitation (GOL) hypothesis, has recently been used to model future impacts of climate warming on fisheries but has not been robustly empirically tested. We used brook trout (Salvelinus fontinalis), a fast-growing, cold-water salmonid species of broad economic, conservation and ecological value, to examine the GOL hypothesis in a long-term experiment quantifying effects of temperature on growth, resting metabolic rate (RMR), maximum metabolic rate (MMR) and gill surface area (GSA). Despite significantly reduced growth and body size at an elevated temperature, allometric slopes of GSA were not significantly different than 1.0 and were above those for RMR and MMR at both temperature treatments (15°C and 20°C), contrary to GOL expectations. We also found that the effect of temperature on RMR was time-dependent, contradicting the prediction that heightened temperatures increase metabolic rates and reinforcing the importance of longer-term exposures (e.g. >6 months) to fully understand the influence of acclimation on temperature-metabolic rate relationships. Our results indicate that although oxygen limitation may be important in some aspects of temperature-body size relationships and constraints on metabolic supply may contribute to reduced growth in some cases, it is unlikely that GOL is a universal mechanism explaining temperature-body size relationships in aquatic ectotherms. We suggest future research focus on alternative mechanisms underlying temperature-body size relationships, and that projections of climate change impacts on fisheries yields using models based on GOL assumptions be interpreted with caution.
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Affiliation(s)
- Joshua K. Lonthair
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- National Research Council under contract to Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA 92037-1508, USA
| | - Nicholas C. Wegner
- Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla 92037-1508, CA, USA
| | - Brian S. Cheng
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Nann A. Fangue
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA 95616, USA
| | - Matthew J. O'Donnell
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Amy M. Regish
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - John D. Swenson
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Estefany Argueta
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Stephen D. McCormick
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Benjamin H. Letcher
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Lisa M. Komoroske
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
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Prinzing TS, Bigman JS, Skelton ZR, Dulvy NK, Wegner NC. The allometric scaling of oxygen supply and demand in the California horn shark, Heterodontus francisci. J Exp Biol 2023; 226:jeb246054. [PMID: 37493039 DOI: 10.1242/jeb.246054] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 07/12/2023] [Indexed: 07/27/2023]
Abstract
The gill surface area of aquatic ectotherms is thought to be closely linked to the ontogenetic scaling of metabolic rate, a relationship that is often used to explain and predict ecological patterns across species. However, there are surprisingly few within-species tests of whether metabolic rate and gill area scale similarly. We examined the relationship between oxygen supply (gill area) and demand (metabolic rate) by making paired estimates of gill area with resting and maximum metabolic rates across ontogeny in the relatively inactive California horn shark, Heterodontus francisci. We found that the allometric slope of resting metabolic rate was 0.966±0.058 (±95% CI), whereas that of maximum metabolic rate was somewhat steeper (1.073±0.040). We also discovered that the scaling of gill area shifted with ontogeny: the allometric slope of gill area was shallower in individuals <0.203 kg in body mass (0.564±0.261), but increased to 1.012±0.113 later in life. This appears to reflect changes in demand for gill-oxygen uptake during egg case development and immediately post hatch, whereas for most of ontogeny, gill area scales in between that of resting and maximum metabolic rate. These relationships differ from predictions of the gill oxygen limitation theory, which argues that the allometric scaling of gill area constrains metabolic processes. Thus, for the California horn shark, metabolic rate does not appear limited by theoretical surface-area-to-volume ratio constraints of gill area. These results highlight the importance of data from paired and size-matched individuals when comparing physiological scaling relationships.
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Affiliation(s)
- Tanya S Prinzing
- Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Jennifer S Bigman
- Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
- Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA 98115, USA
| | - Zachary R Skelton
- Ocean Associates Inc., under contract to Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA 92037, USA
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA
| | - Nicholas K Dulvy
- Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6
| | - Nicholas C Wegner
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA
- Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA 92037, USA
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