Ectothermic animals may respond to environmental hypoxia by moving to cooler environments, exhibiting hypoxia induced behavioural hypothermia (HIBH). One benefit of hypothermia is the concomitant lowering of O2 demand, preserving internal partial pressure of O2 (P02) and delaying internal hypoxia. However, thermal acclimation may remove any such benefits. The macro-invertebrate Pacifastacus leniusculus was used as a model organism in which to clarify the role of haemocyanin in mediating responses to hypoxia. Quantifying the functioning of He is fundamental in understanding its importance in transducing environmental hypoxia. The role of temperature in influencing He 02-affinity was examined in crayfish acclimated to SOC, 13°C or 20°C. Increasing the temperature decreased the 02-affinity of He, regardless of acclimation history of the crayfish. The response of He Oy-affinity to variations in L-Iactate, urate, calcium and magnesium concentrations in the haemolymph were quantified as regulators of 02-binding. Effects of modulators in vitro were modelled to aid in the interpretation of He function in vivo; L- lactate was only found to potentiate He O2 binding at YC, however, urate, Ca and Mg all potentiated He 02-affinity, although this was temperature dependent for Ca. The in vivo functioning of He was assessed by determining the arterial and venous content and partial pressures of O2 and CO2, along with pH of haemolymph from crayfish exposed to progressive hypoxia of 9 mm Hg for 24hrs. Crayfish exhibited a tolerance to sustained hypoxia for 24hrs. The behavioural response of P. leniusculus inside a hypoxic thermal gradient was also investigated and found that it did not exhibit HIBH. However, evidence shows P. leniusculus was utilising anaerobic respiration demonstrated by increased haemolymph L-Iactate and glucose concentrations measured after hypoxic exposure. Therefore the response of P. leniusculus to hypoxia was first hyperventilation resulting in respiratory alkalosis, followed by anaerobiosis. ii
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:566820 |
| Date | January 2011 |
| Creators | Morgan, Elizabeth Ann |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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