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Bangor University DOCTOR of PHILOSOPHY Bangor University DOCTOR OF PHILOSOPHY Physiological capacities of Gammarid amphipods to survive environmental change Crichton, Rosemary Award date: 2014 Awarding institution: Bangor University Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 26. Sep. 2021 Physiological capacities of gammarid amphipods to survive environmental change Rosemary Crichton Summary The aim of this thesis was to investigate the abilities of confamilial gammarid amphipods with differing latitudinal distribution patterns to compensate for environmental change and to examine the consequences. Interesting variations were observed in the strategies employed by gammarid amphipods to cope with environmental change. The boreal/temperate species, Gammarus duebeni, exhibits a high upper thermal tolerance and acclimatory ability, but at the cost of reduced growth and reproductive output. The warmer-water G. locusta appears to have a narrower tolerance and reduced ability to adjust to rapid temperature change, but at stable conditions within its thermal window and at higher salinities it is able to out-perform G. duebeni. G. duebeni may therefore be more likely to survive environmental change, but G. locusta populations may be better able to recover from high mortality events. A similar upper thermal limit and temperature independence of metabolic was observed in the subarctic/boreal species G. oceanicus compared with G. duebeni, however G. oceanicus also demonstrated r-selected life history traits. G. oceanicus and G. locusta occupy overlapping geographical ranges and the same low shore niche, but G. oceanicus appears to have a broader tolerance at a lower optimal temperature than G. locusta. Intraspecific variation was observed between two populations of G. duebeni from Wales (53 °N) and Norway (70 °N). Following acclimation to common temperatures, the northern population was characterised by reduced upper thermal limits and rates of oxygen uptake, a greater thermal sensitivity of oxygen uptake, and evidence of the upregulation of protein synthesis and growth rates in the cold. The influence of the combined factors of salinity and temperature on physiological rate processes in G. duebeni was complex. G. duebeni was less able to adjust to rapid temperature change when acclimated to salinities equivalent to full strength seawater than when held in brackish conditions. i Contents Summary i Contents ii List of figures and tables vii Acknowledgments viii Abbreviations ix Chapter 1 – General introduction 1 1.1. Thermal tolerance and thermal sensitivity 3 1.2. Total energy demand 5 1.3. Protein synthesis and associated variables 8 1.4. Growth, protein synthesis retention efficiency, and body size 10 1.5. Life history strategies 15 1.6. Salinity tolerance and osmoregulation 17 1.7. Gammarid amphipods 21 1.8. Aims and objectives 22 Chapter 2 – General methodology 25 2.1. Collection sites 26 2.1.1. Anglesey, Wales, 53 °N 28 2.1.1.1. Collection site 28 2.1.1.2. Temperature profile 28 2.1.2. Isle of Skye, Scotland, 58 °N 29 2.1.3. Tromsø, Norway, 70 °N 30 2.1.3.1. Collection site 30 2.1.3.2. Temperature profile 31 2.1.4. Ny-Ålesund, Svalbard, Norway, 79 °N 32 2.1.5. Comparison of the thermal regimes of Rhoscolyn and Tromsø 33 2.2. Husbandry 35 2.2.1. Transport 35 ii 2.2.2. Husbandry conditions 36 Chapter 3 – Upper critical limits and the effect of temperature acclimation 40 3.1. Abstract 41 3.2. Introduction 41 3.3. Methodology 44 3.3.1. Thermal tolerance of field-acclimatised gammarids 44 3.3.2. Thermal tolerance of acclimated gammarids 46 3.3.3. The influence of rate of warming on upper thermal limits 47 3.3.4. Statistical analysis 47 3.4. Results 48 3.4.1. Thermal tolerance of field-acclimatised gammarids 48 3.4.2. Thermal tolerance of acclimated gammarids 49 3.4.3. The influence of rate of warming on upper thermal limits 52 3.4.4. Summary 53 3.5. Discussion 54 3.5.1. Effect of latitude 54 3.5.2. Effect of temperature acclimation 55 3.5.3. Effect of salinity acclimation on Gammarus duebeni 59 3.5.4. Effect of rate of warming 61 3.5.5. Conclusion 62 Chapter 4 – The effect of acclimation on aerobic metabolism: rates of oxygen uptake and citrate synthase activity 64 4.1. Abstract 65 4.2. Introduction 65 4.3. Methodology 67 4.3.1. Rates of oxygen uptake 67 4.3.1.1. Field-acclimatised juveniles 68 4.3.1.2. Acclimated amphipods 65 4.3.1.3. Calculation of MO2 and Q10 values 70 4.3.2. Citrate synthase activity in acclimated gammarid amphipods 70 iii 4.3.3. Statistical analysis 71 4.4. Results 72 4.4.1. Rates of oxygen uptake in gammarid amphipods 72 4.4.1.1. Field-acclimatised juveniles and long term acclimation of adults 72 4.4.1.2. Six week acclimation of adults 73 4.4.2. Thermal sensitivity of oxygen uptake in acclimated gammarid amphipods 75 4.4.3. Aerobic capacity in acclimated gammarid amphipods 78 4.5. Discussion 80 4.5.1. Resting metabolic rates and thermal sensitivity 80 4.5.2. Aerobic capacity 87 4.5.3. Conclusions 90 Chapter 5 – Thermal responses of protein synthesis and growth 91 5.1. Abstract 92 5.2. Introduction 92 5.3. Methodology 96 5.3.1. Determination of protein synthesis rates 96 5.3.1.1. Injection regime 96 5.3.1.2. Validation of the flooding dose methodology 97 5.3.1.3. Analysing protein synthesis rates 97 5.3.1.4. Calculations 99 5.3.1.5. Statistical analysis 100 5.3.2. Adult growth rates 100 5.3.2.1. Measurements of adult growth rates 100 5.3.2.2. Statistical analysis 101 5.4. Results 101 5.4.1. Protein synthesis rates 101 5.4.1.1. Validation of the flooding dose methodology 101 5.4.1.2. Whole-animal fractional and absolute rates of protein synthesis 103 5.4.1.3. RNA concentrations and activities 105 5.4.2. Adult growth rates 110 5.5. Discussion 111 5.5.1. Whole-animal fractional and absolute rates of protein synthesis 111 iv 5.5.2. RNA concentrations and activities 114 5.5.3. Adult growth rates 116 5.5.4. Conclusions 120 Chapter 6 – Life history of gammarid amphipods: brood size and juvenile growth rates 121 6.1. Abstract 122 6.2. Introduction 122 6.3. Methodology 125 6.3.1. Brood size 125 6.3.2. Juvenile growth rates 126 6.3.3. Statistical analysis 127 6.4. Results 128 6.4.1. Brood size 128 6.4.2. Juvenile growth rates 129 6.5. Discussion 132 6.5.1. Brood size 132 6.5.2. Juvenile growth rates 137 6.5.3. Conclusions 141 Chapter 7 – General discussion 143 7.1. Gammarus duebeni 144 7.1.1. Effects of temperature on thermal tolerances & biological rate processes 144 7.1.2.Effects of temperature on growth 145 7.1.3. Effects of temperature on life history traits 146 7.1.4. Effects of temperature plus salinity 147 7.1.5. Effects of latitude 148 7.1.6. Effects of season 149 7.1.7. Summary 150 7.2. Gammarus locusta 150 7.3. Gammarus oceanicus 153 7.4. Summary 154 v 7.5. Future directions 155 References 157 vi List of figures and tables Chapter 1 – General introduction Table 1.1. Body size and growth rates of Gammarus species……………………………………………….. 14 Table 1.2 Reproductive outputs of Gammarus species……………………………………………………….. 16 Chapter 2 – General methodology Figure 2.1. Map of sites and species distributions…………………………………………………………………. 26 Table 2.1 Location of the collection sites and Gammarus species sampled…………………………. 27 Figure 2.2 Rhosneigr and Rhoscolyn, Anglesey, Wales…………………………………………………………. 29 Figure 2.3. In situ temperatures, Isle of Skye, Scotland…………………………………………………………. 30 Figure 2.4. Tromsø, Norway………………………………………………………………………………………………….. 31 Figure 2.5. In situ habitat temperatures, Norway………………………………………………………………….. 33 Figure 2.6. In situ temperature comparison, Wales and Norway…………………………………………… 34 Table 2.2. In situ temperatures during collection months, Wales and Norway…………………….. 35 Table 2.3 Acclimation temperatures and salinities……………………………………………………………… 38 Chapter 3 – Upper critical limits and the effect of temperature acclimation Table 3.1. Acclimation conditions………………………………………………………………………………………… 46 Figure 3.1. Upper thermal limits in acclimatised gammarid amphipods………………………………… 49 Figure 3.2. Upper thermal limits in G. duebeni (53 and 70 °N)………………………………………………. 50 Figure 3.3. Percentage mortality of G. duebeni according to temperature (53 °N)………………... 51 Figure 3.4. Upper thermal limits in G. duebeni and G. locusta (53 °N)…………………………………… 52 Figure 3.5. Effect of rate of warming on thermal limits in G. duebeni……………………………………. 53 Chapter 4 – The effect of acclimation on metabolism: rates of oxygen uptake and citrate synthase activity Table 4.1. Acclimation conditions………………………………………………………………………………………… 69 Figure 4.1. Rates of oxygen uptake in acclimatised juveniles………………………………………………… 72 Figure 4.2. Rates of oxygen uptake in acclimated adults……………………………………………………….. 73 Figure 4.3. Rates of oxygen uptake in G.
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