Interpreting species, intraspecific and intra-individual variability by comprehensively characterizing a fish’s respiratory phenotype with valid measures of oxygen uptake

• Main Author: Zhang, Yangfan
• Format: Text
• Language: English
• Published: University of British Columbia 2021
• Subjects: Sockeye; Atlantic salmon
• Online Access: https://dx.doi.org/10.14288/1.0396683; https://doi.library.ubc.ca/10.14288/1.0396683

Vertebrate life is sustained by aerobic metabolism and temporary bouts of anaerobic metabolism. Steady-state aerobic metabolism can be assessed by measuring whole-organism oxygen uptake (ṀO₂), the core of Fry’s paradigm, which becomes a part of a respiratory phenotype that also includes anaerobic capacity. In fishes, environment profoundly affects respiratory phenotype, perhaps even determining migratory and reproductive successes, partially driven by hypoxia, increased thermal and pathogen load. Understanding how such factors affect capacity, functional costs and mortality needs a more accurate, precise, and comprehensive characterization of a fish’s respiratory phenotype. Hence, I developed an Integrated Respiratory Assessment Paradigm (IRAP) to characterize a respiratory phenotype (its needs, capacities & patterns) for individual fish that responds to Fry’s paradigm (controlling, limiting, masking, directive, and lethal factors). Chapter 2 describes an IRAP protocol that measures 14 metrics in 8 fish simultaneously over 3 days, a high sampling throughput to better bridge physiology-&-ecology. Chapter 3 introduces and validates new analytical approaches that improved the resolution and accuracy of maximum ṀO₂ (ṀO₂max) estimations in aquatic respirometry. Chapter 4 illustrates the detection sensitivity of the refined IRAP by distinguishing respiratory phenotypes among three rainbow trout strains using differences in ṀO₂max, absolute aerobic capacity, critical oxygen saturation (O₂crit) and hypoxia tolerance. Moreover, high aerobic and anaerobic capacities correlated with high hypoxic and thermal tolerances among these strains. Chapter 5 explores how acclimation to hypoxia affects the respiratory phenotype, discovering hypoxia-acclimated European sea bass suppress standard metabolic rate (SMR) and O₂crit, a respiratory phenotype better suited for exploiting hypoxic habitats. Chapter 6 explores the diagnostic power of the refined IRAP by assessing the load-dependent changes to SMR, O₂crit, daily energy expenditure and routine ṀO₂ of a high-virulence infectious hematopoietic necrosis virus infection in sockeye salmon and a low-virulence piscine orthoreovirus infection in sockeye and Atlantic salmon. Chapter 7 assesses the repeatability of IRAP indices, showing four traits for aerobic capacity, routine ṀO₂ and time spend above 50% absolute aerobic scope were particularly repeatable. Chapter 8, therefore, synthesizes that high-resolution and reproducible metabolic phenotyping better poises ichthyologists to develop an individual-based metabolic model and integrate it with a Genomic-Physiology-Ecology axis.