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1.
José L. Ardanaz Ana Silva Omar Macadar 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2001,187(11):853-864
At the southern boundary of gymnotiform distribution in America. water temperature changes seasonally, and may be an environmental cue for the onset of breeding. In this study, we aim to describe the role of temperature upon electric organ discharge waveform in Gymnotus carapo, order Gymnotiformes, family Gymnotidae, and to analyze its interactions with the effects of steroid hormones. The effects of water temperature within its natural range were explored using different protocols. All fish tested had temperature-sensitive electric organ discharge waveforms: the amplitude of the last head-negative component (V4) decreased as temperature increased. Rate increases elicited by electrical stimulation had similar but smaller effect on waveform. Temperature sensitivity is a peripheral phenomenon that depends on the conductivity of the aquatic media. We found hormonal-dependent changes in the electric organ discharge waveform not previously described in this species. The amplitude and duration of V4 increased after testosterone administration. Both testosterone treatment and acclimation by sustained temperature at 27-28 degrees C (environmental simulation of breeding conditions) induced a decrease in temperature sensitivity. As in the related species Brachyhypopomus pinnicaudatus, our data strongly suggest interactions between temperature sensitivity of the electric organ discharge waveform and sexual maturity that might be crucial for reproduction. 相似文献
2.
C. R. Franchina P. K. Stoddard 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,183(6):759-768
The electric organ discharge of the gymnotiform fish Brachyhypopomus pinnicaudatus is a biphasic waveform. The female's electric organ discharge is nearly symmetric but males produce a longer second phase
than first phase. In this study, infrared-sensitive video cameras monitored the position of unrestrained fish, facilitating
precise measurement of electric organ discharge duration and amplitude every 2 h for 24 h. Males (n=27) increased electric organ discharge duration by 37 ± 12% and amplitude by 24 ± 9% at night and decreased it during the
day. In contrast, females (n=8) exhibited only minor electric organ discharge variation over time. Most of a male's increase occurred rapidly within the
first 2–3 h of darkness. Electric organ discharge values gradually diminished during the second half of the dark period and
into the next morning. Modulation of the second phase of the biphasic electric organ discharge produced most of the duration
change in males, but both phases changed amplitude by similar amounts. Turning the lights off at mid-day triggered an immediate
increase in electric organ discharge, suggesting modification of existing ion channels in the electric organ, rather than
altered genomic expression. Exaggeration of electric organ discharge sex differences implies a social function. Daily reduction
of duration and amplitude may reduce predation risk or energy expenditure.
Accepted: 12 September 1998 相似文献
3.
G. von der Emde H. Bleckmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,181(5):511-524
Electroreceptive afferents from A- and B-electroreceptor cells of mormyromasts and Knollenorgans were tested for their sensitivity
to different stimulus waveforms in the weakly electric fish Gnathonemus petersii. Both A- and B-mormyromast cells had their lowest sensitivity to a waveform similar to the self-generated electric organ
discharge (EOD) (around 0° phase-shift). Highest sensitivities, i.e. lowest response thresholds, in both A- and B-cells were
measured at phase shifts of +135°. Thus, both cell types were inversely waveform tuned. The sensitivity of B-cells increased
sharply with increasing waveform distortions. Their tuning curves had a sharp minimum of sensitivity at +7° phase shift. A-cells
had a much broader waveform tuning with a plateau level of low sensitivity from +24° to −15°. Across a 360° cycle of phase-shifts,
the range of thresholds was 16 dB for individual B-cells and 4.5 dB for individual A-cells. Knollenorgan afferents were tuned
to 0° phase-shifted EODs and had a dynamic range of 12 dB. Lowest sensitivities were measured at a phase shift of +165°. Experiments
with computer-generated stimuli revealed that the strong sensitivity of mormyromast B-cells of EOD waveform distortions cannot
be attributed to any of the seven waveform parameters tested. In addition, EOD stimuli must have the correct duration for
B-cells to respond to waveform distortions. Thus, waveform tuning appears to be based on the specific combination of several
waveform parameters that occur only with natural EODs.
Accepted: 28 April 1997 相似文献
4.
5.
G. von der Emde 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(2):217-224
Weakly electric fish can detect nearby objects and analyse their electric properties during active electrolocation. Four
individuals of the South American gymnotiform fish Eigenmannia sp., which emits a continuous wave-type electric signal, were tested for their ability to detect capacitive properties of
objects and discriminate them from resistive properties. For individual fish, capacitive values of objects had to be greater
than 0.22–1.7 nF (`lower threshold') and smaller than 120–680 nF (`upper threshold') in order to be detected. The capacitive
values of natural objects fall well within this detection range. All fish trained could discriminate unequivocally between
capacitive and resistive object properties. Thus, fish perceive capacitive properties as a separate object quality. The effects
of different types of objects on the locally occurring electric signals which stimulate electroreceptors during electrolocation
were examined. Purely resistive objects altered mainly local electric organ discharge (EOD) amplitude, but capacitive objects
with values between about 0.5 and 600 nF changed the timing of certain EOD parameters (phase-shift) and EOD waveform. A mechanism
for capacitance detection in wave-type electric fish based on time measurements is proposed and compared with the capacitance
detection mechanism in mormyrid pulse-type fish, which is based on waveform measurements.
Accepted: 31 July 1997 相似文献
6.
C. R. Franchina 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,181(2):111-119
I recorded the electric organ discharges (EODs) of 331 immature Brachyhypopomus pinnicaudatus 6–88 mm long. Larvae produced head-positive pulses 1.3 ms long at 7 mm (6 days) and added a second, small head-negative phase
at 12 mm. Both phases shortened duration and increased amplitude during growth. Relative to the whole EOD, the negative phase
increased duration until 22 mm and amplitude until 37 mm. Fish above 37 mm produced a “symmetric” EOD like that of adult females.
I stained cleared fish with Sudan black, or fluorescently labeled serial sections with anti-desmin (electric organ) or anti-myosin
(muscle). From day 6 onward, a single electric organ was found at the ventral margin of the hypaxial muscle. Electrocytes
were initially cylindrical, overlapping, and stalk-less, but later shortened along the rostrocaudal axis, separated into rows,
and formed caudal stalks. This differentiation started in the posterior electric organ in 12-mm fish and was complete in the
anterior region of fish with “symmetric” EODs. The lack of a distinct “larval” electric organ in this pulse-type species weakens
the hypothesis that all gymnotiforms develop both a temporary (larval) and a permanent (adult) electric organ.
Accepted: 1 March 1997 相似文献
7.
Wilson RS James RS Johnston IA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(2):117-124
Among amphibians, the ability to compensate for the effects of temperature on the locomotor system by thermal acclimation
has only been reported in larvae of a single species of anuran. All other analyses have examined predominantly terrestrial
adult life stages of amphibians and found no evidence of thermal acclimatory capacity. We examined the ability of both tadpoles
and adults of the fully aquatic amphibian Xenopus laevis to acclimate their locomotor system to different temperatures. Tadpoles were acclimated to either 12 °C or 30 °C for 4 weeks
and their burst swimming performance was assessed at four temperatures between 5 °C and 30 °C. Adult X. laevis were acclimated to either 10 °C or 25 °C for 6 weeks and their burst swimming performance and isolated muscle performance
was determined at six temperatures between 5 °C and 30 °C. Maximum swimming performance of cold-acclimated X. laevis tadpoles was greater at cool temperatures and lower at the highest temperature in comparison with the warm-acclimated animals.
At the test temperature of 12 °C, maximum swimming velocity of tadpoles acclimated to 12 °C was 38% higher than the 30 °C-acclimation
group, while at 30 °C, maximum swimming velocity of the 30 °C-acclimation group was 41% faster than the 12 °C-acclimation
group. Maximum swimming performance of adult X. laevis acclimated to 10 °C was also higher at the lower temperatures than the 25 °C acclimated animals, but there was no difference
between the treatment groups at higher temperatures. When tested at 10 °C, maximum swimming velocity of the 10 °C-acclimation
group was 67% faster than the 25 °C group. Isolated gastrocnemius muscle fibres from adult X. laevis acclimated to 10 °C produced higher relative tetanic tensions and decreased relaxation times at 10 °C in comparison with
animals acclimated to 25 °C. This is only the second species of amphibian, and the first adult life stage, reported to have
the capacity to thermally acclimate locomotor performance.
Accepted: 28 October 1999 相似文献
8.
Ruxandra F. Sîrbulescu Günther K. H. Zupanc 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2010,196(5):359-368
Temperature manipulation has been shown to significantly affect recovery after spinal cord injury in various mammalian model
systems. Little has been known thus far about the impact of temperature on structural and functional recovery after central
nervous system lesions in regeneration-competent, poikilotherm organisms. In the present study, we addressed this aspect using
an established model of adult spinal cord regeneration, the weakly electric teleost fish Apteronotus
leptorhynchus. We observed an overall beneficial effect of increased temperature on both structural and behavioral recovery after amputation
of the caudal spinal cord. Fish kept at 30°C recovered the amplitude of the electric organ discharge at more than twice the
rate observed in fish kept at 22°C, within the first 20 days post-injury. This improved recovery was supported by increased
cell proliferation and decreased apoptosis levels in fish kept at 30°C. The high temperature appeared to have a direct inhibitory
effect on apoptosis and to lead to a compression of the duration of the wave of post-lesion apoptosis. The latter effect was
presumably induced through the acceleration of the metabolic rate, a phenomenon also supported by the observation that re-growth
of the tail was significantly increased in fish kept at 30°C. 相似文献
9.
Dimitris G. Sfakianakis Ioannis Leris Maroudio Kentouri 《Environmental Biology of Fishes》2011,90(4):421-427
It is widely known that water temperature affects the swimming capacity of fish. But the effect of the rearing temperature
on the swimming ability of the fish at later stages, has not had similar attention. In this study, four populations of zebrafish,
were reared in different water temperatures (22, 25, 28 and 31°C) and after being acclimatized in a common temperature (26.5°C)
for over a month, they were subjected to swimming trials in order to evaluate the maximum relative critical velocity (RU
crit
) in each case. Fish that were reared in 22°C showed statistically significant lower performance than the ones reared in 31°C
(7.72 ± 0.17 vs. 8.79 ± 0.28, means ± S.E.). Possible explanations for the observed differentiation could be the effect of
early life temperature on fish muscle ontogeny or on body shape. 相似文献
10.
Jeffrey R. Ziegeweid Cecil A. Jennings Douglas L. Peterson 《Environmental Biology of Fishes》2008,82(3):299-307
Many populations of shortnose sturgeon, Acipenser brevirostrum, in the southeastern United States continue to suffer from poor juvenile recruitment. High summer water temperatures, which
may be exacerbated by anthropogenic activities, are thought to affect recruitment by limiting available summer habitat. However,
information regarding temperature thresholds of shortnose sturgeon is limited. In this study, the thermal maximum method and
a heating rate of 0.1°C min−1 was used to determine critical and lethal thermal maxima for young-of-the-year (YOY) shortnose sturgeon acclimated to temperatures
of 19.5 and 24.1°C. Fish used in the experiment were 0.6 to 35.0 g in weight and 64 to 140 days post hatch (dph) in age. Critical
thermal maxima were 33.7°C (±0.3) and 35.1°C (±0.2) for fish acclimated to 19.5 and 24.1°C, respectively. Critical thermal
maxima significantly increased with an increase in acclimation temperature (p < 0.0001). Lethal thermal maxima were 34.8°C (±0.1) and 36.1°C (±0.1) for fish acclimated to 19.5 and 24.1°C, respectively.
Lethal thermal maxima were significantly affected by acclimation temperature, the log10 (fish weight), and the interaction between log10(fish weight) and acclimation temperature (p < 0.0001). Thermal maxima were used to estimate upper limits of safe temperature, thermal preferences, and optimal growth
temperatures of YOY shortnose sturgeon. Upper limits of safe temperature were similar to previous temperature tolerance information
and indicate that summer temperatures in southeastern rivers may be lethal to YOY shortnose sturgeon if suitable thermal refuge
cannot be found. 相似文献
11.
Effects of hypothermic hypoxia on anaerobic energy metabolism in isolated anuran livers 总被引:1,自引:0,他引:1
C. A. Fedorow T. A. Churchill N. M. Kneteman 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(8):555-561
Many lower vertebrates (reptilian and amphibian species) are capable of surviving natural episodes of hypoxia and hypothermia.
It is by specific metabolic adaptations that anurans are able to tolerate prolonged exposure to harsh environmental stresses.
In this study, it was hypothesized that livers from an aquatic frog would possess an inherent metabolic ability to sustain
high levels of ATP in an isolated organ system, providing insight into a metabolic system that is well-adapted for low temperature
in vitro organ storage. Frogs of the species, R. pipiens were acclimated at 20 °C and at 5 °C. Livers were preserved using a clinical preservation solution after flushing. Livers
from 20 °C-acclimated frogs were stored at 20 °C and 5 °C and livers from 5 °C-acclimated frogs were stored at 5 °C. The results
indicated that hepatic adenylate status was maintained for 96 h during 5 °C storage, but not longer than 4–10 h during 20 °C
storage. In livers from 5 °C-acclimated animals subjected to 5 °C storage, ATP was maintained at 100% throughout the 96-h
period. Warm acclimation (20 °C) and 20 °C storage resulted in poorer maintenance of ATP; energy charge values dropped to
0.50 within 2 h and by 24 h, only 24% of control ATP remained. Lactate levels remained less than 25 μ mol/g dry weight in
all 5 °C-stored livers; 20 °C-stored livers exhibited greater accumulation of this anaerobic end-product (lactate reached
45–50 μ mol/g by 10 h). The data imply that hepatic adenylate status is largely dependent on exposure to hypothermic hypoxia
and although small amounts of ATP were accounted for by anaerobic glycolysis, there must have been either a substantial reduction
in cellular energy-utilization or an efficient use of low oxygen tensions.
Accepted: 24 August 1998 相似文献
12.
The conduction properties of peripheral nerves from the Arctic fish species Arctic eelpouts (Lycodes sp.), snake blenny (Lumpenus lampretaeformis) and polar cod (Boreogadus saida), permanently adapted to low temperatures, were studied. Nerves of these fishes have two types of fibres, characterised by
extracellular compound action potentials with fast (7 m/s) and slow (4 m/s) conduction velocities, as measured at 12 °C. The
temperature dependence of the conduction velocity was bimodal, changing its slope at about 16 °C. The Q
10 above 16 °C was 1.12–1.49, while below 16 °C it was 1.82–2.16. Irreversible deterioration of the nerve was observed at temperatures
around 19–27 °C. A comparison with data previously obtained from Mediterranean fishes indicates that Arctic fishes have similar
temperature sensitivity of nerve conduction and a slight vertical displacement on the conduction velocity-temperature curves,
which is insufficient to compensate the decrease of the conduction velocity at their physiological temperature, the conduction
velocity of Arctic fishes being about one-half of that of temperate fishes. This suggests that this neurophysiological function
is not fully cold-adapted in these Arctic fish species.
Accepted: 3 June 2000 相似文献
13.
D. Audet D. W. Thomas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):146-152
The present study questions whether hypothermia is an artifact due to captivity-induced stress or a thermoregulatory strategy
for bats of the neotropical family Phyllostomidae. In Guanacaste, Costa Rica, Carollia perspicillata and Sturnira lilium exhibited a bimodal distribution of body temperatures when submitted to an ambient temperature of 21 °C. Body temperature
was highly correlated with body mass in both species. C. perspicillata of mass ≥20 g and S. lilium of mass ≥17 g remained normothermic (body temperature >37 °C), whereas at masses below 18 g and 13 g, respectively, >80%
of individuals were hypothermic (body temperature ≤32 °C). In two treatment groups for each species, we restricted food intake
to ca. 20% of body mass on either night 1 or night 4 following capture. Hypothermia was significantly related to food-restriction,
but not time in captivity. Metabolic rate (ml O2 · g−1 h−1) at ambient temperature = 21 °C was MR = e
(–2.11 + 0.101 Tb) (r
2 = 0.7, P < 0.001) for C. perspicillata and MR = e
(−2.62 + 0.115 Tb) (r
2 = 0.89) for S. lilium. Free-ranging, radio tagged C. perspicillata exhibited daily depression of body temperature to 33–34 °C. We conclude that hypothermia is an thermoregulatory strategy
that allows phyllostomid bats to adjust metabolic rate to feeding success and the level of fat stores.
Accepted: 20 August 1996 相似文献
14.
Thermal acclimation of locomotor performance in tadpoles of the frog Limnodynastes peronii 总被引:3,自引:0,他引:3
R. S. Wilson C. E. Franklin 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(6):445-451
Previous analyses of thermal acclimation of locomotor performance in amphibians have only examined the adult life history
stage and indicate that the locomotor system is unable to undergo acclimatory changes to temperature. In this study, we examined
the ability of tadpoles of the striped marsh frog (Limnodynastes peronii) to acclimate their locomotor system by exposing them to either 10 °C or 24 °C for 6 weeks and testing their burst swimming
performance at 10, 24, and 34 °C. At the test temperature of 10 °C, maximum velocity (Umax) of the 10 °C-acclimated tadpoles was 47% greater and maximum acceleration (Amax) 53% greater than the 24 °C-acclimated animals. At 24 °C, Umax was 16% greater in the 10 °C-acclimation group, while there was no significant difference in Amax or the time taken to reach Umax (T-Umax). At 34 °C, there was no difference between the acclimation groups in either Umax or Amax, however T-Umax was 36% faster in the 24 °C-acclimation group. This is the first study to report an amphibian (larva or adult) possessing
the capacity to compensate for cool temperatures by thermal acclimation of locomotor performance. To determine whether acclimation
period affected the magnitude of the acclimatory response, we also acclimated tadpoles of L. peronii to 10 °C for 8 months and compared their swimming performance with tadpoles acclimated to 10 °C for 6 weeks. At the test
temperatures of 24 °C and 34 °C, Umax and Amax were significantly slower in the tadpoles acclimated to 10 °C for 8 months. At 10 °C, T-Umax was 40% faster in the 8-month group, while there were no differences in either Umax or Amax. Although locomotor performance was enhanced at 10 °C by a longer acclimation period, this was at the expense of performance
at higher temperatures.
Accepted: 25 June 1999 相似文献
15.
R. W. Rose N. Kuswanti E. Q. Colquhoun 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):359-363
Marsupials at birth are ectothermic and gradually attain the ability to change their metabolic heat production during pouch
life. How this process occurs in the bettong has been measured on 13 pouch young from week 1 until 3 weeks after pouch vacation
(week 18). Oxygen consumption was measured at 35 °C (pouch temperature) and at 22 °C. The results at 35 °C showed an increase
in metabolic rate from week 1 until week 12 when there was a decrease to near adult levels after pouch vacation. At 22 °C
young bettongs had a lower metabolic rate (compared with measurements made at 35 °C) until week 9 after which there was an
increase above measurements made at 35 °C. Noradrenaline had little effect until week 10 after which the metabolic rate (although
measured at 35 °C) paralleled the levels measured at 22 °C. The free thyroxine level was low in early pouch life, increased
to a peak at week 12 then decreased. Thermal conductance increased until week 10 after which it decreased, reaching values
similar to those of adult bettongs by week 20. The results indicate that non-shivering thermogenesis occurs in this macropodoid
marsupial. This phenomenon may be a phylogenetic difference between macropodid and non-macropodid marsupials as also suggested
by Nicol et al. (1997).
Accepted: 19 February 1998 相似文献
16.
D. T. Booth 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):399-404
Incubation temperature and the amount of water taken up by eggs from the substrate during incubation affects hatchling size
and morphology in many oviparous reptiles. The Brisbane river turtle Emydura signata lays hard-shelled eggs and hatchling mass was unaffected by the amount of water gained or lost during incubation. Constant
temperature incubation of eggs at 24 °C, 26 °C, 28 °C and 31 °C had no effect on hatchling mass, yolk-free hatchling mass,
residual yolk mass, carapace length, carapace width, plastron length or plastron width. However, hatchlings incubated at 26 °C
and 28 °C had wider heads than hatchlings incubated at 24 °C and 31 °C. Incubation period varied inversely with incubation
temperature, while the rate of increase in oxygen consumption during the first part of incubation and the peak rate of oxygen
consumption varied directly with incubation temperature. The total amount of oxygen consumed during development and hatchling
production cost was significantly greater at 24 °C than at 26 °C, 28 °C and 31 °C. Hatchling mass and dimensions and total
embryonic energy expenditure was directly proportional to initial egg mass.
Accepted: 18 March 1998 相似文献
17.
Booth DT Thompson MB Herring S 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(4):269-276
Eggs of two small Australian lizards, Lampropholis guichenoti and Bassiana duperreyi, were incubated to hatching at 25 °C and 30 °C. Incubation periods were significantly longer at 25 °C in both species, and
temperature had a greater effect on the incubation period of B. duperreyi (41.0 days at 25 °C; 23.1 days at 30 °C) than L. guichenoti (40.1 days at 25 °C; 27.7 days at 30 °C). Patterns of oxygen consumption were similar in both species at both temperatures,
being sigmoidal in shape with a fall in the rate of oxygen consumption just prior to hatching. The higher incubation temperature
resulted in higher peak and higher pre-hatch rates of oxygen consumption in both species. Total amount of oxygen consumed
during incubation was independent of temperature in B. duperreyi, in which approximately 50 ml oxygen was consumed at both temperatures, but eggs of L. guichenoti incubated at 30 °C consumed significantly more (32.6 ml) than eggs incubated at 25 °C (28.5 ml). Hatchling mass was unaffected
by either incubation temperature or the amount of water absorbed by eggs during incubation in both species. The energetic
production cost of hatchling B. duperreyi (3.52 kJ · g−1) was independent of incubation temperature, whereas in L. guichenoti the production cost was greater at 30 °C (4.00 kJ · g−1) than at 25 °C (3.47 kJ · g−1). Snout-vent lengths and mass of hatchlings were unaffected by incubation temperature in both species, but hatchling B. duperreyi incubated at 30 °C had longer tails (29.3 mm) than those from eggs incubated at 25 °C (26.2 mm). These results indicate that
incubation temperature can affect the quality of hatchling lizards in terms of embryonic energy consumption and hatchling
morphology.
Accepted: 27 January 2000 相似文献
18.
Weathers WW Gerhart KL Hodum PJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(8):561-572
We measured resting metabolic rates at air temperatures between ca. −5 and 30 °C in snow petrels (Pagodroma nivea), cape petrels (Daption capense), Antarctic petrels (Thalassoica antarctica), and Antarctic fulmars (Fulmarus glacialoides). We measured seven age classes for each species: adults, and nestlings that were 3, 8, 15, 28, 35, and 42 days old. Basal
metabolic rate (BMR) and thermal conductance (C) of adults averaged, respectively, 140% and 100% of values predicted allometrically
for nonpasserine birds. Minimum metabolic rates of unfasted nestlings aged 15–42 days averaged, respectively, 97% and 98%
of predicted adult BMR in Antarctic petrels and snow petrels, versus 119% and 126% of predicted in Antarctic fulmars and cape
petrels. Nestlings of the southerly breeding snow petrel and Antarctic petrel were relatively well insulated compared with
nestlings of other high-latitude seabirds. Adult lower critical temperature (Tlc) was inversely related to body mass and averaged 9 °C lower than predicted allometrically. As nestlings grew, their Tlc decreased with increasing body mass from ca. 14 to 22 °C (depending upon species) at 3 days of age, to −4 to 8 °C when nestlings
attained peak mass. Nestling Tlc subsequently increased as body mass decreased during pre-fledging weight recession. Nestling Tlc was close to mean air temperature from the end of brooding until fledging in the three surface nesting species.
Accepted: 12 July 2000 相似文献
19.
Thermal sensitivity of mitochondrial function in the Antarctic Notothenioid Lepidonotothen nudifrons 总被引:4,自引:0,他引:4
I. Hardewig H. O. Pörtner L. S. Peck 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):597-604
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.
Accepted: 2 September 1999 相似文献
20.
The influence of low temperature (5–29 °C) on the methanogenic activity of non-adapted digested sewage sludge and on temperature/leachate-adapted
biomass was assayed by using municipal landfill leachate, intermediates of anaerobic degradation (propionate) and methane
precursors (acetate, H2/CO2) as substrates. The temperature dependence of methanogenic activity could be described by Arrhenius-derived models. However,
both substrate and adaptation affected the temperature dependence. The adaptation of biomass in a leachate-fed upflow anaerobic
sludge-blanket reactor at approximately 20 °C for 4 months resulted in a sevenfold and fivefold increase of methanogenic activity
at 11 °C and 22 °C respectively. Both acetate and H2/CO2 were methanized even at 5 °C. At 22 °C, methanogenic activities (acetate 4.8–84 mM) were 1.6–5.2 times higher than those
at 11 °C. The half-velocity constant (K
s) of acetate utilization at 11 °C was one-third of that at 22 °C while a similar K
i was obtained at both temperatures. With propionate (1.1–5.5 mM) as substrate, meth‐anogenic activities at 11 °C were half
those at 22 °C. Furthermore, the residual concentration of the substrates was not dependent on temperature. The results suggest
that the adaptation of biomass enables the achievement of a high treatment capacity in the anaerobic process even under psychrophilic
conditions.
Received: 23 December 1996 / Received last revision: 18 June 1997 / Accepted: 23 June 1997 相似文献