Some factors affecting the respiration of some aquatic plants

Summary The oxygen consumption of four aquatic plants has been determined at various concentrations of dissolved oxygen and at three different temperatures.Oxygen consumption rates (mg oxygen/g dry weight per hr) at 20°C in air-saturated water were Berula erecta, 1.25; Callitriche obtusangula, 2.8; Hippuris vulgaris, 1.96; and Ranunculus pseudofluitans, 1.90.Oxygen consumption rates increased with increase in dissolved-oxygen concentration within the experimental limits of 1.2–17 p.p.m. dissolved oxygen. The relation of oxygen consumption to this range of oxygen concentrations can be described by the empirical equation R = aC ^b. Increase of temperature has been shown to increase the rates of oxygen consumption. Q₁₀ values ranging from 1.32 to 3.48 have been obtained.     

Responsiveness of Amaranthus retroflexus seeds to ethephon, 1-aminocyclopropane 1-carboxylic acid and gibberellic acid in relation to temperature and dormancy

Dormant Amaranthus retroflexus seeds do not germinate in the dark at temperatures below 35°C. Fully dormant seeds germinate only at 35–40°C whereas non-dormant ones germinate within a wider range of temperatures (15 to 40°C). Germination of non-dormant seeds requires at least 10% oxygen, but the sensitivity of seeds to oxygen deprivation increases with increasing depth of dormancy. 10^–6 to 10^–4 M ethephon, 10^–3 M 1-aminocyclopropane 1-carboxylic acid (ACC) and 10^–3 M gibberellic acid (GA₃) break this dormancy. In the presence of 10^–3 M GA₃ dormant seeds are able to germinate in the same range of temperatures as non-dormant seeds. The stimulatory effect of GA₃ is less dependent on temperature than that of ethephon, while ACC stimulates germination only at relatively high temperatures (25–30°C). The results obtained are discussed in relation to the possible involvement of endogenous ethylene in the regulation of germination of A. retroflexus seeds.Abbreviations ACC 1-aminocyclopropane 1-carboxylic acid - GA₃ gibberellic acid - SD standard deviation     

Temperature preferences and oxygen consumption of three species of sculpin (Cottus) from the Pit River drainage,California

Synopsis I examined the temperature preferences and routine metabolic rates of Pit sculpin, Cottius pitensis, marbled sculpin, C. klamathensis macrops, and rough sculpin, C. asperrimus, of the Pit River drainage of California to determine if the distributional patterns of these species can be explained on the basis of physiological or behavioral responses to temperature. The routine metabolic rates of these species did not increase significantly between 10 and 15°C, indicating an area of thermal compensation. Metabolic rates then rapidly increased between 15 and 20°C (Q₁₀ values>4.0) followed by little increase between 20 and 25°C (Q₁₀ values >2.0), indicating another area of thermal compensation. The final temperature preferenda of Pit, marbled and rough sculpin were 11.2, 12.1 and 13.5°C, respectively. Marbled and rough sculpin appear to be more stenothermal than Pit sculpin. At acclimation temperatures of 10, 15 and 20°C the acute preferred temperatures of marbled and rough sculpin ranged from 11.1 to 14.7° C and 13.3 to 14.4°C, respectively. Values for Pit sculpin ranged from 9.9 to 16.4°C at acclimation temperatures of 10, 15 and 20°C. The distributions of marbled and rough sculpin are consistent with their behavioral and metabolic responses to temperature. The widespread distribution of Pit sculpin is consistent with its greater tolerance of high temperatures and eurythermal behavior, but the absence of Pit sculpin from habitats dominated by marbled and rough sculpin is not consistent with a temperature related explanation.     

Impact of acute temperature transition on enzyme activity levels,oxygen consumption,and exogenous fuel utilization in sea raven (Hemitripterus americanus) hearts

Summary The impact of an acute temperature transition between 5 °C and 15 °C on energy metabolism and performance of sea raven (Hemitripterus americanus) heart was assessed. Maximal in vitro activity of hexokinase was 1.2 and 3.7 mol · min^-1 · g^-1 at 5 °C and 15 °C, respectively. Carnitine palmitoyl transferase and carnitine palmitoleoyl transferase activities were 0.07 mol · min^-1 · g^-1 at 15 °C and declined substantially at 5 °C. Oxygen consumption and power output of perfused isolated hearts offered glucose alone as a metabolic fuel decreased significantly between 15 °C and 5 °C. When palmitoleate was included in the perfusion medium, oxygen consumption and power development remained constant between 15 °C and 5 °C, suggesting that glucose alone was not an adequate metabolic fuel at low temperature. However, maximal in vitro activity of HK implied that the catalytic potential at this locus was quite capable of meeting demands of carbon flow, while the maximal in vitro activity of the carnitine acyl CoA transferases implied that fatty acid metabolism should be greatly compromised at low temperatures. In an effort to resolve the contradiction, hearts were perfused with medium containing ¹⁴C-glucose or ¹⁴C-palmitate. Rates of ¹⁴CO₂ production from labelled metabolic fuels could account for only about 2% of the oxygen consumption rates. Most of the label from ¹⁴C-glucose was incorporated into the glycogen and lipid fractions and label from ¹⁴C-palmitate was incorporated into the lipid fraction. The net incorporation rates of label into intracellular pools were temperature insensitive over the range 5–15 °C. The incorporation of exogenous glucose into the lipid fraction suggests that activity of the entire glycolytic pathway was maintained over the temperature range. Thus, the relatively low rate of oxygen consumption of hearts perfused with glucose alone as an exogenous substrate cannot be attributed to a limitation of glucose catabolism. The alternative explanation is that the presence of fatty acids induces an increase in oxygen consumption, especially at 5 °C. It is speculated that this is due to alterations in Ca²⁺ balance.Abbreviations ATPase adenosine triphosphatase - BSA bovine serum albumin - CoA coenzyme A - C palmitoyl T carnitine palmitoyl transferase - CS citrate synthase - HK hexokinase - MO oxygen consumption - PFK phosphofructokinase - PO ₂ oxygen partial pressure     

Heat tolerance, behavioural temperature selection and temperature-dependent respiration in larval Octopus huttoni

This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h⁻¹) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CT_max) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae⁻¹ h⁻¹ in one-day old larvae to 40.1-99.4 nmol h⁻¹ at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q₁₀) on 5 days old larvae (Q₁₀=1.35) was lower when compared with the 1 day old larvae (Q₁₀=1.68). The lower Q₁₀ in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species.     

Influence of temperature and ambient oxygen on the swimming energetics of cyprinid larvae and juveniles

Synopsis The relationship between respiration and swimming speed of larvae and juveniles (2–100 mg fresh mass) of Danube bleak, Chalcalburnus chalcoides (Cyprinidae), was measured at 15° and 20° C under hypoxic (50% air saturation), normoxic, and hyperoxic (140% air saturation) conditions. In a flow-tunnel equipped with a flow-through respirometer the animals swam at speeds of up to 8 lengths · s^-1; speeds were sustained for at least two minutes. The mass specific standard, routine, and active respiration rates declined with increasing body mass at both temperatures. Metabolic intensity increased with temperature, but also the critical swimming speed (at which oxygen uptake reached its maximum) was higher at 20° than at 15° C by about 30%. Nevertheless, the oxygen debt incurred by the fish at the highest speeds was about 40%, and the net cost of swimming about 32%, lower at 20° than at 15°C. The standard metabolic rate was more strongly dependent on temperature (Q₁₀ around 2.5) than the maximum active rate (Q₁₀ below 2). Whereas standard and routine respiration rates were well regulated over the pO₂-range investigated (8.5–25.8 kPa), the active rates showed a conformer-like pattern, resulting in factorial scopes for activity between 2 and 4. Under hypoxia, the critical swimming speed was lower than under normoxia by about 1.51 · s^-1, but the net cost of swimming was also lower by about 30%. On the other hand, hyperoxia neither increased the swimming performance nor did it lead to a further increase of the metabolic cost of swimming. The hypoxia experiments suggest that in response to lowered tensions of ambient oxygen maintenance functions of metabolism not directly related to swimming may be temporarily reduced, leading to increased apparent swimming efficiency under these conditions. The responses of the larvae of Danube bleak to low temperature and low ambient oxygen are discussed in terms of the metabolic strategies by which energy-limited animals meet the challenge of environmental deterioration.     

Respiratory studies on two small freshwater amoebae

The changes in respiration rate and mean cell volume induced by temperature within the range 10°C–25°C were investigated in two small species of freshwater amoebae,Saccamoeba limax Page andVannella sp. Mean cell volume varied in response to temperature, with maxima at 20°C inVannella sp. (10.15× 10³ (±1.80)m³ and 15°C inS. limax (9.08×10³ (±0.93)m³. Respiration rate increased over the temperature range investigated. The highest rates and the greatest rate of increase between temperatures occurred inVannella sp. Q₁₀ ranged between 0.12 and 1.33 inS. limax and between 1.77 and 7.36 inVannella sp. A regression of log oxygen uptake versus log cell volume incorporating the data of the present investigation and the data of other workers on amoeba respiration is presented, and the ecological significance and application of such data discussed.     

Respiratory energy losses in the protozoan predator Didinium nasutum Müller (Ciliophora)

Summary Respiration in Didinium nasutum, an active protozoan predator, was investigated in relation to cell weight at 10, 15, and 20° C by means of cartesian diver microrespirometry. Oxygen uptake increased progressively over the 10–20° C temperature range; a table of Q ₁₀ related to weight is presented. Regression coefficients of log weight versus log oxygen uptake (b) were 0.96 at 10° C, 0.98 at 15° C and 1.00 at 20° C. D. nasutum was shown to expend very much higher levels of respiratory energy than a mainly sedentary carnivorous ciliate of comparable weight.     

The ecology of Synchaeta kitina Rousselet in Loch Leven,Scotland

Synchaeta kitina Rousselet reached population densities of up to 5000 ind.l^–1 in Loch Leven, between January 1977 and December 1982. The species was found over the entire range of temperatures recorded (0.4–21.4 °C), but was most abundant at temperatures above 7 °C. Embryo development times, determined under laboratory conditions, ranged from 122 h at 2 °C to 12.5 h at 20 °C. There was a marked inverse relationship between populations of S. kitina and Daphnia hyalina var. lacustris in the loch. It seems unlikely that this was due to interference competition from Daphnia. S. kitina can be cultured on Rhodomonas minuta var. lacustris and there is some evidence that this rotifer also feeds on small flagellates in its natural environment.     

Temperature aspects of ecological bioenergetics in Brachionas angularis (Rotatoria)

The influence of temperature and food quality was studied on the following energy balance parameters of B. angularis: ingestion, production, growth and mortality. The ingestion rate rises to an optimum at 15 and 20 °C and decreases at 25 °C. The other rates increase continuously over the 5–25 °C range. The Q₁₀-values of production rate are higher than those of ingestion rate. Temperature also modifies the relationship between food concentration and bioenergetic rates. They react according to a Monod function (production at all temperatures, growth at 10 °C) or decrease at high concentrations (growth at 15° and 20 °C.)     

Temperature effect on growth rates of Eriophorum vaginatum roots

Summary Root growth rates of the sedge Eriophorum vaginatum L. were studied under controlled environmental conditions. The air temperature was maintained constant at 15°C while the root temperatures varied in 5°C intervals between 2° and 37° C (12° C excluded). Root growth rates of 1.2 mm d^-1 at 2°, 20.4 mm d^-1 at 32° C and 10.1 mm d^-1 at 37° C were recorded. A Q₁₀ of 3.2 was calculated for the temperature range from 7° to 27° C. Root growth rates at temperatures above 17° C declined after one week of growth. The degree of decline was proportional to the applied root temperature. Depletion of available nonstructural carbohydrate was the probable cause for this decline.     

Respiratory energy losses related to cell weight and temperature in ciliated protozoa

Summary Respiratory energy losses in five species of ciliated protozoa, Tetrahymena pyriformis Ehrenberg, Vorticella microstoma Ehrenberg, Paramecium aurelia Ehrenberg, Spirostomum teres Claparède and Lachmann and Frontonia leucas Ehrenberg, were investigated at 8.5° C, 15° C and 20° C using Cartesian diver microrespirometry. Q ₁₀ values of 1.15–2.24 were found for four of the species between 8.5–15° C, while in S. teres a Q ₁₀ of 12.98 occurred between these temperatures. Between 15–20° C T. pyriformis and P. aurelia had Q ₁₀ values of 3.73 and 1.56, respectively. Linear double log regressions of oxygen consumption vs. dry weight were derived at each temperature and regression coefficients (b) of 0.2723 (8.5° C), 0.4364 (15° C) and 0.4171 (20° C) were obtained. The results are explained and discussed in relation to previous work on the energetics of ciliated protozoa.     

Effect of temperature on growth and nitrogen mineralization of fungi and fungal-feeding nematodes

Dish and column microcosms containing alfalfa-sand medium were established to determine effect of temperature on growth and N mineralization ability of two fungi (Rhizoctonia solaniand Botrytis cinerea) and two nematodes (Aphelenchus avenaeand Aphelenchoides composticola). The microcosms were incubated at 15, 20, 25 and 29 °C for 21 days. In the dish microcosms, hyphal growth rates of both fungal species increased with temperature in the range of 15–25 °C. Above that temperature range, the growth rate of R. solani remained almost constant while that of B. cinereadecrease considerably. The population growth rate of A. avenae increased with temperature between 15 and 29 °C on colonies of R. solani and B. cinerea in dish microcosms. The growth rate of A. composticola also increased in the range of 15–25 °C but decreased greatly beyond that temperature range independent of the fungal species as food source. Inorganic N (NH₄ ⁺ + NO₃ ^–) was collected from each column microcosm by leaching every 3 days. In the columns containing R. solani, there was a significant effect of temperature on the amount of N detected in the fungus+A avenaeor A. composticolabut not in the fungus alone columns. The total amount of N was greatest at 29 °C for A. avenaeand at 20 °C for A. composticola columns, concurrent with the population growth rates of the nematodes. In the columns containing B. cinerea, the effect of temperature on the amount of inorganic N was not significant in either the fungus alone or fungus+nematode columns, although the population growth rates of the both nematode species were highest at 20 °C. For B. cinerea, the N amount across temperatures was the same or larger for the fungus alone as for the fungus+nematode columns. In general, the contribution of fungal-feeding nematodes to N mineralization was small in any combinations of fungus and nematode species at any temperature. Similarity in C/N ratio of the fungal and nematode biomass, organic substrate C/N ratios too low for measurable increase in net mineralization by the nematodes and small reproduction of the nematodes in the column microcosms were probable contributory factors.     

Effects of temperature on growth rates of fungi from subantarctic Macquarie Island and Casey,Antarctica

Summary The linear growth rates of fungal isolates were measured on agar plates at temperatures ranging from 4° to 35°C. Fungi tested included the major fungal colonizers of leaves and litter of the three dominant plant species on subantarctic Macquarie Island, and major fungal species associated with plant and soil communities near Australia's Casey Station on the Antarctic Continent. All fungi grew at 4°C and were classified as psychrotrophs. Maximum growth rates were recorded at temperatures of 10° to 20°C for 13 of the 15 isolates from Macquarie Island and for all six isolates from Casey. Most of the leaf colonizing fungi from Macquarie Island had optimum growth temperatures of 15°C whereas all litter fungi from Macquarie Island and Casey fungi except Thelebolus microsporus had optimum growth temperatures of 20°C or above. Maximum growth of all species was at temperatures above those normally prevailing in their natural environments, with most species growing at 4°C at between 10% and 30% of their maximum rates. However, microclimatic effects may have resulted at times in temperatures near their growth optima. The highest growth rates at 4°C were recorded for Phoma spp. 1 and 2, Phoma exigua and Mortierella gamsii from Macquarie Island and Mortierella sp. 1 from Casey. Thelebolus microsporus and sterile sp. G from Casey also grew relatively fast at 4°C, and these species, and Phoma sp. 3 and Phoma exigua from Macquarie Island had the lowest Q-₁₀ values for the temperature range 4° to 15°C.     

Thermopreference,tolerance and metabolic rate of early stages juvenile Octopus maya acclimated to different temperatures

Thermopreference, tolerance and oxygen consumption rates of early juveniles Octopus maya (O. maya; weight range 0.38–0.78 g) were determined after acclimating the octopuses to temperatures (18, 22, 26, and 30 °C) for 20 days. The results indicated a direct relationship between preferred temperature (PT) and acclimated temperature, the PT was 23.4 °C. Critical Thermal Maxima, (CTMax; 31.8±1.2, 32.7±0.9, 34.8±1.4 and 36.5±1.0) and Critical Thermal Minima, (CTMin; 11.6±0.2, 12.8±0.6, 13.7±1.0, 19.00±0.9) increased significantly (P<0.05) with increasing acclimation temperatures. The endpoint for CTMax was ink release and for CTMin was tentacles curled, respectively. A thermal tolerance polygon over the range of 18–30 °C resulted in a calculated area of 210.0 °C². The oxygen consumption rate increased significantly α=0.05 with increasing acclimation temperatures between 18 and 30 °C. Maximum and minimum temperature quotients (Q₁₀) were observed between 26–30 °C and 22–26 °C as 3.03 and 1.71, respectively. These results suggest that O. maya has an increased capability for adapting to moderate temperatures, and suggest increased culture potential in subtropical regions southeast of México.     

The effects of temperature on the respiration and production of the freshwater nematode Anonchus sp.

Summary Growth and respiration were measured in a species of Anonchus (Nematoda: Plectidae) at 5°C, 10°C, 15°C, 20°C and 25°C. At 5°C no growth was measurable but the organisms remained active. Maximum production occurred at 15°C, but the highest rate of growth occurred at 20°C. Thus, adult size attained is dependent on the temperature of growth. Respiratory energy losses derived from Cartesian diver microrespirometry, increased with temperature up to 25°C. Regression coefficients (b values) derived from a log log linear regression of weight against oxygen consumption varied between 0.574–1.793, the lowest value being attained at 5°C, the highest at 20°C. Based on Q₁₀, production and respiratory energy losses the optimum temperatures for Anonchus appears to lie between 10°C–15°C.     

The dependence of reproductive rate on cell size and temperature in freshwater ciliated protozoa

Summary Reproductive rates have been calculated for ten species of ciliated protozoa in defined conditions. Interspecific double log regressions of generation time vs. cell volume have been computed at each of three temperatures (8.5° C, 15° C, and 20° C) indicating a significant dependence of reproductive rate on cell size. Recorded generation times varied from 6.38 h in Vorticella microstoma at 20° C to 1004 h in Spirostomum teres at 8.5° C. These values correspond to a range in r _m (day)^-1 of 2.607 to 0.017 and (day)^-1 of 13.554 to 1.017. The relationship between these data and similar published data for marine ciliates is examined and the value of such regressions in ecological studies of the protozoa is discussed.     

Rotifer distribution in relation to temperature and oxygen content

Lunzer Obersee, a small lake located at an altitude of 1100 m above sea level, was investigated from July 1985 to October 1987. The rotifer community consists of 7 dominant species, 7 subdominant species and 34 species which occasionally occurred in the plankton. The dominant species show rather different demands in relation to temperature and oxygen content; e.g.: Filinia hofmanni was found at a wide range of oxygen concentrations (0.6–13.3 mg O₂l^–1) and low temperatures (4–6 °O, living in the upper water layers (1–7 m) during spring and in the deeper, anoxic zone in summer. In contrast, Asplanchna priodonta was found at rather high oxygen contents (> 9 mg O₂ l^–1), ), and showed a wide range of temperature tolerance (4–15 °C).On the basis of field data the temperature and oxygen requirements of several species are described and discussed.     

Capacity for sustained terrestrial locomotion in an insect: Energetics,thermal dependence,and kinematics

Summary The capacity for sustained, terrestrial locomotion in the cockroach. Blaberus discoidalis, was determined in relation to running speed, metabolic cost, aerobic capacity, and ambient temperature (T _a=15, 23, and 34°C; acclimation temperature=24°C). Steady-state thoracic temperature (T _tss) increased linearly with speed at each T _a.The difference between T _tss and T _awas similar at each experimental temperature with a maximum increase of 7°C. Steady-state oxygen consumption (VO_2ss) increased linearly with speed at each T _aand had a low thermal dependence (Q₁₀=1.0-1.4). The minimum cost of locomotion (the slope of the VO_2ss versus speed function) was independent of T _a.Cockroaches attained a maximal oxygen consumption (VO_2max). increased with T _afrom 2.1 ml O₂·g^-1·h^-1 at 15°C to 4.9 ml O₂·g^-1·h^-1 at 23°C, but showed no further increase at 34°C, VO_2max increased 23-fold over resting VO₂ at 23°C, 10-fold at 34°C, and 15-fold at 15°C. Endurance correlated with the speed at which VO_2max was attained (MAS, maximal aerobic speed). Temperature affected the kinematics of locomotion. compared to cockroaches running at the same speed, but higher temperatures (23–34°C), low temperature (15°C) increased protraction time, reduced stride frequency, and reduced stability by increasing body pitching. The thermal independence of the minimum cost of locomotion (C_min), the low thermal dependence of VO_2ss (i.e., y-intercept of the VO_2ss versus speed function), and a typical Q₁₀ of 2.0 for VO_2max combined to increase MAS and endurance in B. discoidalis when T _awas increased from 15 to 23°C. Exerciserelated endothermy enabled running cockroaches to attain a greater VO_2max, metabolic scope, and endurance capacity at 23°C than would be possible if T _tss remained equal to T _a. The MAS of B. discoidalis was similar to that of other arthropods that use trachea, but was 2-fold greater than ectotherms, such as salamanders, frogs, and crabs of a comparable body mass.Abbreviations T _a ambient temperature - T _t thoracic temperature - T _tss steady state thoracic temperature during exercise - T _trest thoracic temperature during rest - VO₂ oxygen consumption - VO_2rest oxygen consumption during rest - VO_2ss steady-state oxygen consumption during exercise - VO_2max maximal oxygen consumption; MAS maximum aerobic speed - C _min minimum cost of locomotion - t _end endurance time