Oxygen uptake and delivery in cold temperate marine teleosts

Graham, Mark Stephen (1985) Oxygen uptake and delivery in cold temperate marine teleosts. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Aspects of respiratory and circulatory physiology were investigated in the winter flounder (Pseudopleuronectes americanus) and the sea raven (Hemitripterus americanus). The physical and physiological factors affecting oxygen uptake and delivery were the main foci of the research. Hemoglobin function, blood flow to the tissues, and the operation of cardiac muscle during different seasons were investigated. The influence of temperature on the acclimatization process was investigated. -- A significant difference in oxygen uptake at the gills (V₀₂) was found in the seasonally acclimatized flounder (Q₁₀ = 2.4; winter temperature was 0.5°C, and summer temperature was 9.5°C). Comparable changes were observed in the cardiac output (Vb) and ventilation volume (Vw) of the winter flounder. The gills of winter fish were more resistant to oxygen uptake, yet the oxygen tension of arterial blood (Pₐ₀₂) in winter fish did not differ from that of summer fish. -- A number of findings point to or suggest the causes of changes in oxygen resistance of the gills during seasonal acclimatization. In vitro blood viscosity of the winter flounder, especially at temperatures below 10°C, shows a great sensitivity to changes in temperature. Viscosity measurements in situ indicate that at lower temperatures blood tends to flow through larger, less resistant blood vessels, so that the surface area for oxygen transfer to the blood is limited in winter fish gills. However, a slower blood flow rate during the winter, and seasonal changes in blood components, assist in maintaining arterial oxygen tension. As indicated by studies on the sea raven heart in situ, winter acclimatized fish have diminished ability to produce a cardiac output. During the winter there is a significant increase in concentration of total hemoglobin and a significant shift toward higher hemoglobin-oxygen affinity. -- Intraerythrocytic components such as H⁺, C1⁻, and nucleotide triphosphates (NTP) influence hemoglobin-oxygen affinity in the winter flounder. Temperature influences the concentration of intraerythrocytic modifiers, and seasonal changes tend to support shifts in oxygen affinity. -- It is concluded that temperature plays a significant role in effecting physiological changes during acclimatization to the seasons. The physical effects of temperature upon blood flow and oxygen uptake at the gills are opposed by alterations in blood components meeting metabolic demands while maintaining oxygen tension.

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