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  • 1
    Electronic Resource
    Electronic Resource
    Intracellular pH and energy metabolism in the highly stenothermal Antarctic bivalve Limopsis marionensis as a function of ambient temperature (1999)
    Springer
    Polar biology 22 (1999), S. 17-30 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in oxygen consumption, ammonia excretion and in the acid-base and energy status of various tissues were investigated in the cold stenothermal Antarctic bivalve, Limopsis marionensis, and compared to similar data in the limpet, Nacella concinna, for an assessment of thermal sensitivity. Oxygen consumption of L. marionensis varied between −1.5 and 2°C with a Q 10 of 2.2. Ammonia excretion could only be detected in animals exposed to elevated temperature for periods in excess of 45 days and close to death and it is interpreted as the onset of protein and amino acid catabolism with starvation under temperature stress. In L. marionensis any change in temperature as well as starvation stress at constant temperature induced a decrease in phospho-l-arginine and ATP levels. However, only temperature stress resulted in a drop in the Gibb's free energy change of ATP hydrolysis. Intracellular pH rose in all tissues during upward or downward temperature changes of only 1.5 or 2°C for 24 h with a concomitant trend to accumulate succinate and acetate in the tissues. These changes are seen to reflect disturbances of the tissue acid-base and energy status with any under- or overshoot in aerobic metabolic rate during a temperature decrease or increase. Elevated temperature at 2°C during 2 weeks of incubation resulted in continued net ATP depletion, at low levels of ATP free energy. This indicates long-term stress, which was also mirrored in the inability to establish a new steady-state mean rate of oxygen consumption. Incubation at even higher temperatures of 4 and 7°C led to an aggravation of energetic stress and transition to an intracellular acidosis, as well as a fall in oxygen consumption. In N. concinna a drop in energy levels was also visible at 2°C but was compensated for during long-term incubation. In conclusion, L. marionensis will be able to compensate for a temperature change only in a very narrow range whereas the thermal tolerance window is much wider in N. concinna. The inability of the metabolic rate to rise continually and the concomitant transition to anaerobic metabolism and long-term energetic stress characterize the upper critical temperature. Stenothermality is discussed, not only as reflecting the permanent and very stable low temperature in the natural environment, but also regarding dif- ferences in the level of activity and aerobic scope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050386
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  • 2
    Electronic Resource
    Electronic Resource
    Extra- and intracellular acid-base balance and ionic regulation in cod (Gadus morhua ) during combined and isolated exposures to hypercapnia and copper (1997)
    Springer
    Marine biology 128 (1997), S. 337-346 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cod (Gadus morhua) were exposed to hypercapnia (water Pco2 = 7.5 mmHg), elevated copper level (0.4 ppm) or a combination of both in order to study extra- and intracellular acid-base regulation and the influence hereupon of copper. During pure hypercapnia, the extracellular respiratory acidosis was completely compensated within 12 to 24 h via a chloride-mediated increase in extracellular [HCO3 −]. Exposure to copper in normocapnic seawater caused a large and progressive increase in plasma [Na+] and [Cl−] and a metabolic acidosis. Exposure to copper in hypercapnic seawater was associated with smaller elevations of plasma [Na+] and [Cl−] than in normocapnic seawater, showing that hypercapnia had a protective effect on the copper-induced osmoregulatory disturbances. The compensation of the hypercapnic acidosis was, however, slow and incomplete in fish exposed to both copper and hypercapnia. Extracellular pH remained depressed by 0.3 pH units after 72 h. The data reveal that acid-base regulation was immediately and persistently inhibited by copper. The limited acid-base regulation during combined copper and hypercapnia exposure was chloride-mediated as during hypercapnia alone. Intracellular pH recovery was complete and very rapid in ventricular and skeletal muscle tissues during environmental hypercapnia, whereas acid-base compensation in liver tissue was slower, the kinetics being similar to that in the extracellular compartment. Intracellular pH compensation was significantly slowed down by copper. Copper concentration increased drastically in gill tissue already at 3 h, while copper concentrations in liver, muscle and plasma were significantly elevated only after 48 h, with liver showing the largest elevation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050099
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  • 3
    Electronic Resource
    Electronic Resource
    Energy metabolism and ATP free-energy change of the intertidal worm Sipunculus nudus below a critical temperature (1996)
    Springer
    Journal of comparative physiology 166 (1996), S. 492-500 
    Details
    ISSN: 1432-136X
    Keywords: Key words Cold-induced anaerobiosis ; Acid-base status ; Blood gas parameters ; Gibb’s free-energy change of ATP hydrolysis ; Intracellular pH ; Critical temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The intertidal worm Sipunculus nudus was exposed to various temperatures for an analysis of the integrated changes in energy and acid-base status. Animals were incubated in sea water or maintained for up to 8 days at 4 and 0 °C while dwelling in the sediment. Cannulation of the animals prior to experimentation allowed the analysis of blood gas parameters (P O2, P CO2 and pH). P O2 fell to 0 torr within 8 days at 0 °C. A simultaneous reduction of ventilatory activity was derived from measurements of the pattern of coelomic fluid pressure changes associated with ventilatory movements. The increase in P CO2 and an onset of anaerobic metabolism, indicated by the accumulation of end products like acetate and propionate both in the coelomic fluid and the body wall musculature, led to the development of a progressive acidosis and a deviation from the alphastat regulation of intracellular pH seen in unburied animals. The drop in intracellular pH together with the depletion of the adenylates and the phosphagen, phospho-L-arginine, reflect a significant decrease in the Gibb’s free-energy change of ATP hydrolysis. These changes are interpreted to indicate lethal cold injuries, because recovery was not possible when the animals were returned to 12 °C after more than 2 days of exposure to 0 °C. A low critical temperature indicating the onset of cold-induced anaerobiosis is concluded to exist below 4 °C owing to the insufficient response of the ventilatory system to the developing hypoxia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050037
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature induced anaerobiosis in two populations of the polychaete worm Arenicola marina (L.) (1997)
    Springer
    Journal of comparative physiology 167 (1997), S. 25-35 
    Details
    ISSN: 1432-136X
    Keywords: Key words Acid-base status  ;  Alpha-stat regulation  ;  Anaerobic metabolism  ;  Cold adaptation  ;  Critical temperatures  ;  Intracellular pH  ;  Temperature adaptation  ;  Volatile fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Temperature dependent changes in the mode of energy metabolism and in acid-base status were studied in the range from −1.7 to 26 °C in two populations of Arenicola marina collected in summer as well as in winter from intertidal flats of the North Sea (boreal) and the White Sea (subpolar). Extreme temperatures led to an accumulation of anaerobic end products, indicating the existence of both a low and a high critical temperature, beyond which anaerobic metabolism becomes involved in energy production. In summer animals from the North Sea the high critical temperature was found at temperatures above 20 °C, and the low critical temperature below 5 °C. Latitudinal or seasonal cold adaptation lead to a more or less parallel shift of both high and low critical temperature values to lower values. Between critical temperatures intracellular pH declined with rising temperature. Slopes varied between −0.012 and −0.022 pH- units/°C. In summer animals from the North Sea, the slope was slightly less than in White Sea animals, but differences appeared independent of the season. However, slopes were no longer linear beyond critical temperatures. A drop in intracellular pH at low temperatures coincided with the accumulation of volatile fatty acids in the body wall tissue of North Sea animals. A failure of active pHi adjustment is held responsible for the reduced ΔpHi/ΔT at temperatures above the high critical temperature. Extracellular pH was kept constant over the whole temperature range investigated. The ability of North Sea animals to adapt to temperatures beyond the critical temperature is poor compared to White Sea specimens. The larger range of temperature fluctuations at the White Sea is seen as a reason for the higher adaptational capacity of the subpolar animals. A hypothesis is proposed that among other mechanisms critical temperature values are set by an adjustment of mitochondrial density and thus, aerobic capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050044
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  • 5
    Electronic Resource
    Electronic Resource
    Energy metabolism and ATP free-energy change of the intertidal wormSipunculus nudus below a critical temperature (1996)
    Springer
    Journal of comparative physiology 166 (1996), S. 492-500 
    Details
    ISSN: 1432-136X
    Keywords: Cold-induced anaerobiosis ; Acid-base status ; Blood gas parameters ; Gibb's free-energy change of ATP hydrolysis ; Intracellular pH ; Critical temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The intertidal wormSipunculus nudus was exposed to various temperatures for an analysis of the integrated changes in energy and acid-base status. Animals were incubated in sea water or maintained for up to 8 days at 4 and 0°C while dwelling in the sediment. Cannulation of the animals prior to experimentation allowed the analysis of blood gas parameters ( $$P_{O_2 } $$ , $$P_{CO_2 } $$ and pH). $$P_{O_2 } $$ fell to 0 torr within 8 days at 0°C. A simultaneous reduction of ventilatory activity was derived from measurements of the pattern of coelomic fluid pressure changes associated with ventilatory movements. The increase in $$P_{CO_2 } $$ and an onset of anaerobic metabolism, indicated by the accumulation of end products like acetate and propionate both in the coelomic fluid and the body wall musculature, led to the development of a progressive acidosis and a deviation from the alphastat regulation of intracellular pH seen in unburied animals. The drop in intracellular pH together with the depletion of the adenylates and the phosphagen, phospho-l-arginine, reflect a significant decrease in the Gibb's free-energy change of ATP hydrolysis. These changes are interpreted to indicate lethal cold injuries, because recovery was not possible when the animals were returned to 12°C after more than 2 days of exposure to 0°C. A low critical temperature indicating the onset of cold-induced anaerobiosis is concluded to exist below 4°C owing to the insufficient response of the ventilatory system to the developing hypoxia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02338292
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal sensitivity of mitochondrial function in the Antarctic Notothenioid Lepidonotothen nudifrons (1999)
    Springer
    Journal of comparative physiology 169 (1999), S. 597-604 
    Details
    ISSN: 1432-136X
    Keywords: Key words Antarctic fish ; Temperature ; Mitochondrial respiration ; Proton leakage ; Isocitrate dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The thermal sensitivity of mitochondrial function was investigated in the stenothermal Antarctic fish Lepidonotothen nudifrons. State 3 respiration increases with increasing temperature between 0 °C and 18 °C with a Q 10 of 2.43–2.63. State 4 respiration in the presence of oligomycin, an inhibitor of mitochondrial ATP synthase, quantifies the leakage of protons through the inner mitochondrial membrane, which causes oxygen consumption without concomitant ATP production. This parameter shows an unusually high Q 10 of 4.21 ± 0.42 (0–18 °C), which indicates that proton leakage does not depend merely on ion diffusion but is an enzyme-catalysed process. The differential thermal sensitivity of oxidative phosphorylation (=state 3) and proton leakage (=state 4 in the presence of oligomycin) leads to progressive uncoupling of the mitochondria and decreased efficiency of oxidative phosphorylation under in vivo conditions if the body temperature of L. nudifrons increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050260
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  • 7
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    Extra- and intracellular acid-base balance and ionic regulation in cod ( Gadus morhua  ) during combined and isolated exposures to hypercapnia and copper (1997)
    Springer
    Details
    Publication Date: 1997-05-20
    Print ISSN: 0025-3162
    Electronic ISSN: 1432-1793
    Topics: Biology
    Published by Springer
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    PAPER CURRENT
  • 8
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    Coordination of metabolism, acid‐base regulation and haemocyanin function in cephalopods (1995)
    Overseas Publ. Assoc.
    In:  Marine and Freshwater Behaviour and Physiology, 25 (1-3). pp. 131-148.
    Details
    Publication Date: 2020-07-08
    Description: The role of cephalopod haemocyanins in oxygen transport is analysed in the light of the coordination of metabolism, acid‐base regulation and gas exchange processes. Results obtained in squid, the most active among cephalopod species, indicate that the pH dependence of their haemocyanin supports a Po2‐buffer function for the pigment. The release of base equivalents from the tissue during aerobic exercise and the minimal release of protons during anaerobic octopine formation protect arterial pH and, thus, oxygen binding. The extent of respiratory acidification and haemocyanin deoxygenation on the venous side is higher in blood returning from the mantle than from the head. In vivo blood gas measurements reported for squid and for other cephalopod species support the conclusion that CO2 accumulation and respiratory acidification of the blood occur in excess of the effect expected from the consumption of haemocyanin bound O2 and RQ values derived from protein catabolism. This suggests that a considerable fraction of the oxygen consumed by the animal enters via the skin, especially in the mantle. Model calculations demonstrate that skin O2 uptake in the mantle increases during activity in squid. In other cephalopod species like cuttlefish, the special process of arterial CO2 binding to oxygenated haemocyanin and its release during venous deoxygenation may provide the excess CO2 required for venous acidification. All of these processes allow the classical Bohr effect to function supporting oxygen loading at the gills and oxygen unloading in the tissues. The large pH‐dependent cooperativity and the Bohr effect combine to maximize the Po2‐buffer function of the respiratory pigment. These adaptations probably evolved after the ancestors of modern cephalopods lost their shells and locomotor activity assumed a greater role in their lifestyle.
    Type: Article , PeerReviewed
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  • 9
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    A review of ammonia‐mediated buoyancy in squids (cephalopoda: Teuthoidea) (1995)
    Overseas Publ. Assoc.
    In:  Marine and Freshwater Behaviour and Physiology, 25 (1-3). pp. 193-203.
    Details
    Publication Date: 2020-07-08
    Description: Some deep water squids are known to achieve neutral buoyancy by storing ammonium in their body tissues. The Cranchiidae use a unique coelomic cavity to store ammoniacal fluid; in 15 other families, ammonium appears to be sequestered in either vacuoles in the active body tissues or in a gelatinous outer layer. The hypothesis that these squids form a single lineage is here reconsidered through reviews of morphological characters that could support this hypothesis and physiological mechanisms that could contribute to the repeated evolution of ammonium storage. No readily apparent character identifies all ammoniacal squids as belonging to a single lineage, although 5 families of tissue ammoniacal squids appear to be monophyletic. If the elaborate funnel locking apparatus of this group arose within the clade, it is not homologous with that in other taxa, refuting a basis on which close relationships were suggested for ammoniacal squids. Given the limited data available, we question whether some squids considered to be ammoniacal may develop these characters as a result of senescence. Squids are all thought to derive energy from amino acid catabolism, produce large quantities of ammonia and have very low blood pH's which effectively remove ammonia from cells that produce it. They also minimize H+ ion transfer between muscle cells and blood. These features may be important preadaptations for ammonium storage. Given the physiological data, and the absence of morphological evidence supporting monophyly, we argue that ammoniacal squids be best considered to be a polyphyletic group, evolved in parallel.
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  • 10
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    Environmental constraints and the physiology of performance in squids (1998)
    Taylor & Francis
    In:  South African Journal of Marine Science, 20 (1). pp. 207-221.
    Details
    Publication Date: 2021-06-28
    Description: The highly active squid which inhabit the pelagic zones of continental seas are characterized by high energy requirements and have been termed invertebrate athletes. In this paper, the physiological and biochemical background of muscular performance in squid from different environments is reviewed and the physiological and environmental factors limiting performance levels are addressed. One important factor is the highly concentrated haemocyanin which, in ommastrephid squid, and by virtue of their extreme pH dependence, helps to load oxygen efficiently in the gills and unload it fully into the tissues. Squid regulate their extracellular pH more efficiently than intracellular pH, so protecting the haemocyanin from fatal pH changes. However, a large proportion of the oxygen requirement in the mantle muscle must still be provided by oxygen uptake through the skin. Anaerobic mechanisms become involved beyond critical swimming speeds once oxygen supply to mitochondria becomes limiting. Onset of anaerobiosis also characterizes the limits of long-term tolerance to progressive hypoxia at a critical P O2 and to high, above-critical temperatures. In general, anaerobic energy production reflects an inability to meet oxygen demand and indicates transition to a time-limited situation. The development of energy-saving locomotion strategies therefore shifts critical thresholds and extends tolerance periods in species exposed to environmental extremes, typically in coastal areas. There, negatively buoyant squid make greater use of the fin for economical swimming, which is also advantageous because of the complexity of the environment. In Lolliguncula brevis, the rate at which anaerobic resources are used above the critical swimming velocity is minimized by oscillating between periods of high and low pressure jets, thereby extending the period during which the animal can dive into hypoxic or warm water. However, only jet propulsion can economically attain the high velocities necessary in the open sea. Accordingly, the highest performance levels are seen in squid inhabiting the open sea, and they are only made possible by the uniform environmental parameters. Some squid may be able to operate at their functional and environmental limits, revealing a trade-off between oxygen availability, temperature, performance level and, possibly, body size.
    Type: Article , PeerReviewed
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