Respiratory Physiology of Neomyxine biniplicata, the Slender Hagfish A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science in Biological Sciences University of Canterbury By Catherine Philippa Edwards University of Canterbury, New Zealand 2019 Table of Contents List of Figures ..................................................................................................................... ix List of Tables ..................................................................................................................... xii Abstract............................................................................................................................. xiii Acknowledgements ......................................................................................................... xv Chapter One Introduction ..................................................................................................... 1 1.1 Family Myxinidae ......................................................................................................... 1 1.2 The Palaeozoic Era ........................................................................................................ 2 1.3 The Ostracoderms ......................................................................................................... 3 1.4 Early vertebrate evolution and relationships ........................................................... 3 1.5 Sub-families of Myxinidae ........................................................................................... 7 1.6 Myxinidae of New Zealand ......................................................................................... 7 1.7 Myxinidae: ecology, commerce and conservation ................................................... 8 1.8 Population trend of Neomyxine biniplicata ............................................................ 10 1.9 General characteristics of Myxinidae anatomy ...................................................... 10 1.10 Oxygen in the marine environment ....................................................................... 13 1.11 Adaptation to hypoxia and anoxia ......................................................................... 15 1.12 The cardiovascular system ...................................................................................... 16 1.13 Respiration and ventilation ..................................................................................... 16 1.14 Marine environment of New Zealand ................................................................... 17 1.15 Environmental temperature .................................................................................... 17 1.16 Range and environment of Neomyxine biniplicata ............................................. 18 1.17 Neomyxine biniplicata ............................................................................................. 18 Chapter Two General experimental methods ................................................................... 23 iii 2.1 Ethics and consent....................................................................................................... 23 2.2 Capture of experimental animals ............................................................................. 23 2.3 Aquarium ..................................................................................................................... 24 2.4 Substrate ....................................................................................................................... 25 2.5 Feeding regime ............................................................................................................ 25 2.6 Identification ................................................................................................................ 26 2.7 Experimental set-up .................................................................................................... 26 2.8 Retrieval of specimens from the aquarium ............................................................. 26 2.9 Lighting ........................................................................................................................ 27 2.10 Circadian rhythm ...................................................................................................... 27 2.11 Data collection and calibration of Firesting oxygen meter ................................. 28 2.12 Statistical Analysis .................................................................................................... 29 Chapter Three Ventilatory response to acute changes of temperature ......................... 31 3.1 Introduction ................................................................................................................. 31 3.2. Metabolism and temperature ................................................................................... 31 3.3 Thermal acclimation ................................................................................................... 32 3.4 Temperature range of Myxinidae held in captivity ............................................... 34 3.5 The effects of specific dynamic action ...................................................................... 35 3.6 Stroke volume .............................................................................................................. 36 3.7 Respiratory anatomy of hagfish ................................................................................ 36 3.8 Experimental series ..................................................................................................... 39 3.9 Material and Methods ................................................................................................ 39 3.9.1 Effect of temperature on ventilatory rate ......................................................... 40 3.9.2 Small experiments of interest but no statistical value .................................... 40 iv 3.9.3 Method I ................................................................................................................ 40 3.9.4 Method II ............................................................................................................... 41 3.9.5 Method III.............................................................................................................. 42 3.10 Summer and Winter Populations ........................................................................... 43 3.11 Calculations and statistical analysis ....................................................................... 44 3.12 Results ......................................................................................................................... 44 3.12.1 Water temperature ............................................................................................. 44 3.12.2 Ventilatory rate and temperature .................................................................... 45 3.12.3 Ventilatory rates in the summer population .................................................. 45 3.12.4 Ventilatory rates in the winter population. .................................................... 45 3.12.5 Comparison of ventilatory rates between seasonal populations ................ 46 3.12.6 Q10 values ............................................................................................................. 46 3.12.7 SDA ...................................................................................................................... 46 3.12.8 Comparison of ventilatory rates between N. biniplicata and E. cirrhatus 46 3.13 Statistical analysis ..................................................................................................... 47 3.14 Discussion .................................................................................................................. 51 3.14.1 Response to acute temperature changes and differences between seasonal populations .................................................................................................................... 51 3.14.2 Acclimation to seasonal temperatures ............................................................ 52 3.14.3 Ventilation in other species of Myxinidae ...................................................... 54 3.14.4 Ventilatory rate in the native E. cirrhatus ...................................................... 55 3.14.5 Ventilation in M. glutinosa ............................................................................... 55 3.14.6 Effect of SDA on ventilatory rate in N. biniplicata ....................................... 56 3.15 Summary .................................................................................................................... 56 v Chapter Four Routine metabolic rate and critical oxygen tension in Neomyxine biniplicata: two experimental methods ............................................................................... 59 4.1 Metabolic rate .............................................................................................................. 59 4.2 Oxygen consumption as a proxy for metabolic rate .............................................. 59 4.3 Specific dynamic action .............................................................................................. 60 4.4 Environment, temperature and metabolic rate ...................................................... 61 4.5 The state and effect of hypoxia ................................................................................. 62 4.6 Critical