Respiratory metabolism of temperature acclimated Fundulus heteroclitus (L.): Zones of compensation and dependence

The oxygen consumption of temperature acclimated mummichogs, Fundulus heteroclitus (L.) weighing ≈0.1–10.0 g, was measured at 5, 13, 21, and 29 C. Between 13 and 21°C and 21 and 29°C, the values of Q₁₀ were 1.55 and 1.04, respectively, indicating relative thermal independence of respiratory metabolic rate over this 16°C range (Q₁₀ = 1.27). This range encompasses the normal late spring, summer, and early fall range of habitat temperature in Maine estuaries, so that mummichogs are able to grow and reproduce relatively independent of environmental temperature. Between 5 and 13°C, respiratory metabolism is very temperature sensitive (Q₁₀ = 4.42) indicating a substantial reduction of metabolic processes at low temperatures. This enables mummichogs to conserve any metabolic reserves during the coldest months. The regression of log weight-specific oxygen consumption on log body weight was determined at each experimental temperature. All had significantly negative slopes indicating the importance of body size in mummichog respiration.     

Evidence of temperature‐independent metabolic rates in diurnal Namib Desert tenebrionid beetles

To investigate whether the sensitivity to environmental temperature varies between nocturnal and diurnal species of tenebrionid beetle, the metabolic rates of three diurnal species (Onymacris plana Peringuey, Onymacris rugatipennis Haag and Physadesmia globosa Haag) and three nocturnal species (Epiphysa arenicola Penrith, Gonopus sp. and Stips sp.) of beetles from the Namib Desert are measured over a range of temperatures (15–40 °C) that are experienced by these beetles in their natural habitat. The diurnal species O. plana, O. rugatipennis and P. globosa exhibit temperature‐independent metabolic rates (mean Q₁₀ = 1.2) within temperature ranges that are ecologically relevant for diurnal desert beetles (30–40 °C). Onymacris plana, in particular, has a 20–40 °C rate–temperature slope (0.007 log₁₀ mL O₂ h^?1 g^?1 °C^?1; Q₁₀ = 1.1) that is less than half that of the other five beetle species (0.022–0.063 log₁₀ mL O₂ h^?1 g^?1 °C^?1; Q₁₀ ranges from 1.3–1.9), suggesting that O. plana is more metabolically independent of temperature than the other nocturnal and diurnal tenebrionids being investigated. Animals with metabolic rates that are decoupled from body temperature (or ambient temperature) may have an ecological advantage that allows them to exploit thermal and spatial niches during extreme temperature conditions.     

Adaptation of soil microbial growth to temperature: Using a tropical elevation gradient to predict future changes

Terrestrial biogeochemical feedbacks to the climate are strongly modulated by the temperature response of soil microorganisms. Tropical forests, in particular, exert a major influence on global climate because they are the most productive terrestrial ecosystem. We used an elevation gradient across tropical forest in the Andes (a gradient of 20°C mean annual temperature, MAT), to test whether soil bacterial and fungal community growth responses are adapted to long‐term temperature differences. We evaluated the temperature dependency of soil bacterial and fungal growth using the leucine‐ and acetate‐incorporation methods, respectively, and determined indices for the temperature response of growth: Q₁₀ (temperature sensitivity over a given 10oC range) and T_min (the minimum temperature for growth). For both bacterial and fungal communities, increased MAT (decreased elevation) resulted in increases in Q₁₀ and T_min of growth. Across a MAT range from 6°C to 26°C, the Q₁₀ and T_min varied for bacterial growth (Q_10–20 = 2.4 to 3.5; T_min = ?8°C to ?1.5°C) and fungal growth (Q_10–20 = 2.6 to 3.6; T_min = ?6°C to ?1°C). Thus, bacteria and fungi did not differ significantly in their growth temperature responses with changes in MAT. Our findings indicate that across natural temperature gradients, each increase in MAT by 1°C results in increases in T_min of microbial growth by approximately 0.3°C and Q_10–20 by 0.05, consistent with long‐term temperature adaptation of soil microbial communities. A 2°C warming would increase microbial activity across a MAT gradient of 6°C to 26°C by 28% to 15%, respectively, and temperature adaptation of microbial communities would further increase activity by 1.2% to 0.3%. The impact of warming on microbial activity, and the related impact on soil carbon cycling, is thus greater in regions with lower MAT. These results can be used to predict future changes in the temperature response of microbial activity over different levels of warming and over large temperature ranges, extending to tropical regions.     

Temperature Dependency of Circadian Period in a Single Cell (Acetabularia)

The circadian rhythm in the oxygen production of 30 individual Acetabularia cells has been studied at different temperatures. The temperature induced period variation was continuously evaluated over the whole data record of each individual cell with an advanced spectral analysis technique. The observed circadian periods of O₂ production displayed a well established region of temperature compensation between 25 °C and 30 °C with a Q₁₀, value of 0.9, whereas between 15°C and 22°C a positive temperature coefficient was measured (Q₁₀ at 22 °C 0.9, Q₁₀ at 20°C 0.8, Q₁₀at 17°C 0.7).     

The role of temperature in enhancing the insecticidal activity of Bacillus thuringiensis against Spodoptera littoralis larvae

The present study scrutinised how far temperature would affect the velocity of the insecticidal activity of Bacillus thuringiensis, as the rapidity of pest control achievements is of a great concern. Third instar Spodoptera littoralis larvae were treated with Bt at three concentration levels under five different temperatures (15°C, 20°C, 25°C, 30°C and 35°C). LT₅₀s were evaluated in each case. The LT₅₀ values showed various levels of reductions as temperature and/or Bt concentration increased, indicating that the velocity of mortality (1/LT₅₀) and/or the rapidity of Bt activity was almost temperature dependant. However, relatively high and low reduction percentages in the LT₅₀ values on the elevation of 5°C were obtained at lower and higher temperature ranges, respectively. The temperature coefficient, Q ₁₀ values, determined within narrow ranges (5°C) showed great reductions when temperature increased from 15°C to 20°C at all Bt concentrations. Raising temperature by 5°C above 20°C or 25°C almost caused similar Q ₁₀ values indicating constant increase in the response of Bt activity within 20–30°C temperature range. Q ₁₀ values over 30°C were comparatively very low. This proved that decrease in Q ₁₀ values due to the rise of temperature was dependant on the starting temperature.     

Growth of swimming muscles and its metabolic cost in larvae of whitefish at different temperatures

The temperature relationship of routine metabolic rate (R_r) of non-feeding, non-growing Coregonus lavaretus larvae between 2 and 15°C is characterized by Q₁₀-values ranging from l.8-2.45. The rate of growth, based on weight determinations, of first-feeding larvae amounted to 3.5, 7.6 and 9.4% day-¹ at 5, 10 and 12°C respectively, from which Q₁₀-values between 4.0 and 4.8 can be calculated. The rate of increase of muscle mass between 5 and 10°C, based on the determination of the cross-sectional area of inner muscle fibres, resulted in a Q₁₀-value of 4.5. Water temperature influenced the pattern of growth of the inner muscle fibres. At hatching, after 360 day degrees, total muscle mass of larvae reared at 4 and 8°C was independent of temperature, but at 4°C the rate of mass increase owed more to hyperplasia (increase in fibre number) than to hypertrophy (increase in fibre mass), whereas at 8°C the opposite was the case. The calculation of power budgets (including the metabolic cost of growth) of first-feeding larvae yielded net conversion efficiencies (K₂) increasing with temperature from 46.3% at 5°C to 54.7% at 12°C. Comparing our data with literature data two general conclusions can be drawn. (1) In first-feeding larvae the net, but not the gross, conversion efficiency of food energy increases with temperature. This is due to net energy input being characterized by a much higher Q₁₀-value than energy expenditures. (2) In embryos of freshwater fish so far investigated hyperplasia plays a greater role in the increase of fibre mass than hypertrophy at the lower temperature, whereas in embryos of marine fish hyperplasia prevails at the higher temperature. It is suggested that this discrepancy correlates with the high concentration of free amino acids in the eggs of marine species which provide an additional, easily available, source of metabolic energy absent in freshwater species.     

Thermal dependence of clearance and metabolic rates in slow- and fast-growing spats of manila clam Ruditapes philippinarum

Thermal dependence of clearance rate (CR: l h^?1), standard (SMR: J h^?1) and routine metabolic rates (RMR: J h^?1), were analyzed in fast (F)- and slow (S)-growing juveniles of the clam Ruditapes philippinarum. Physiological rates were measured at the maintenance temperature (17 °C), and compared with measurements performed at 10 and 24 °C after 16 h and 14 days to analyze acute and acclimated responses, respectively. Metabolic rates (both RMR and SMR) differed significantly between F and S seeds, irrespective of temperature. Mass-specific CRs were not different for F and S seeds but were significantly higher in F clams for rates standardized according to allometric size-scaling rules. Acute thermal dependency of CR was equal for F and S clams: mean Q ₁₀ were ≈3 and 2 in temperature ranges of 10–17 and 17–24 °C, respectively. CR did not change after 2 weeks of acclimation to temperatures. Acute thermal effects on SMR were similar in both groups (Q ₁₀ ≈ 1 and 1.6 in temperature ranges of 10–17 and 17–24 °C, respectively). Large differences between groups were found in the acute thermal dependence of RMR: Q ₁₀ in F clams (≈1.2 and 1.9 at temperature ranges of 10–17 and 17–24 °C, respectively) were similar to those found for SMR (Q ₁₀ = 1.0 and 1.7). In contrast, RMR of S clams exhibited maximum thermal dependence (Q ₁₀ = 3.1) at 10–17 °C and become depressed at higher temperatures (Q ₁₀ = 0.9 at 17–24 °C). A recovery of RMR in S clams was recorded upon acclimation to 24 °C. Contrasting metabolic patterns between fast and slow growers are interpreted as a consequence of differential thermal sensitivity of the fraction of metabolism associated to food processing and assimilation.     

Metabolic responses to temperature change in a tropical freshwater copepod (Mesocyclops brasilianus) and their adaptive significance

Summary Metabolic rates of Mesocyclops brasilianus from Lake Valencia, Venezuela, were determined at several temperatures spanning the environmental range (22–28° C). The QO₂'s (oxygen consumption per unit weight) of all Mesocyclops stages from Lake Valencia are higher than most but not all QO₂'s from temperate copepod species that have been studied. The QO₂ is essentially static through naupliar development and shows a sudden jump between N6 and CI, which probably results from the major change in morphology and behavior at this point in the life history. QO₂ declines steadily between CI and adult stages. Acclimated copepodite and adult Mesocyclops show a decreasing metabolic rate with increasing temperature (i.e. Q₁₀< 1.0) over the temperature range 26–28° C. This is the range of temperatures normally encountered during the daily vertical migration when the lake is thermally stratified (April–November). Since vertical migration would result in a compromise between a fully acclimated and an acute response, a nearly constant metabolic rate or a slight decline in metabolic rate in the warmer water would be expected in field populations. The results thus show that the metabolic rate of Mesocyclops is not reduced when it moves into deeper (cooler) water, as would be predicted by certain energy-based hypotheses that have been used to explain vertical migration. In contrast to the low Q₁₀'s between 26 and 28° C, copepodites and adults have very high Q₁₀ values in the range 22–26° C. This indicates an adaptive decrease in metabolic rate which is thermally programmed to coincide with the cooler temperatures that are encountered during the mixing season (December–March), when a drastic change in ecological conditions occurs in the lake.Nauplii show evidence of the same seasonal response but without the superimposed plateau at high temperatures, which they would not need because they are weak migrators. Nauplii show a plateau at the lowest temperatures, however, which suggests that a fixed metabolic reduction occurs at the onset of mixing and metabolism is not altered thereafter with declining temperature.The change in QO₂ with temperature generally supports the hypothesis that all Mesocyclops stages are adapted to hold a high, constant metabolic rate through the diel cycle but experience a seasonal reduction in metabolic rate in response to major ecological changes in the lake at the time of seasonal mixing.     

Relative Protein Metabolism in Rotifer Brachionus calyciflorus PALLAS,in Relation to Temperature

In the temperature range of 10 to 35°C the relationships of the oxygen consumption and nitrogen excretion rates to temperature in Brachionus calyciflorus PALLAS can be described by an exponential function where Q₁₀ is equal to 2.45 or 2.18, respectively. Temperature adaptation within the range studied resulted in stabilisation of relative protein metabolism which accounted for nearly 50 per cent of the total metabolic loss.     

Physiological flexibility: the key to success and survival for Antarctic fairy shrimps in highly fluctuating extreme environments

1. The anostracan fairy shrimp Branchinecta gaini inhabits one of the most hostile environments on earth, living in pools and lakes in Antarctica. Between January 2002 and January 2003 temperatures in two pools where B. gaini are extremely abundant on Adelaide Island ranged from ?18.6 to ?15.7 °C in winter, to 19.4 to 17.1 °C in summer, whilst air temperatures ranged from ?34 to 6.3 °C. 2. Branchinecta gaini survives winter as cysts, but endures large summer temperature fluctuations as adults. Cysts froze between ?24.4 and ?25.7 °C. In experiments adults survived 0–10 °C with no mortality for 1 week, 25 °C for nearly 48 h with 50% mortality, and at 32 °C complete mortality occurred in <1 h. 3. Oxygen consumption (M?O₂) in B. gaini approximately doubled for every 10 °C temperature rise (Q₁₀ = 2.04) up to 20 °C where it reached a peak. Females had, on average 19% higher M?O₂ than males. Females also had greater metabolic scopes, (maximum–minimum M?O₂ across temperatures was ×3.6 for females, ×3.1 for males). 4. Ventilation frequency increased linearly with temperature, and did not decline at 25 °C, indicating animals were ‘trying’ progressively harder to supply oxygen to tissues, and oxygen deficiency was the probable cause of death. Females had a higher ventilation frequency than males (8.6–17.1% higher) and they also exhibited greater scope to raise ventilation frequency (×2.4 for females versus ×1.5 for males). 5. Great metabolic flexibility allows B. gaini to exploit extreme, highly fluctuating environments, and larger ventilatory and respiratory scopes allow females to survive higher temperatures than males. Because of this flexibility their prospects for coping with physical environmental change are high.     

Thermal sensitivity of white muscle lactate dehydrogenase isolated from a lake trout, (<Emphasis Type="Italic">Salmo trutta</Emphasis>), inhabiting lake Plav,Montenegro

To shed light on thermoadaptive properties of Salmo trutta from lake Plav (Montenegro), we undertook kinetic studies of pyruvate reduction rates and thermal stability analyses of white muscle LDH. We compared these with the data obtained for trout of the same, confirmed by us, Danubian lineage living in rivers and streams of Serbia and Montenegro. We also tested the effect of acclimation in captivity at 4 and 14 °C. The lake trout was of a typical smoltified phenotype (the size, the elongated silver colored body). At physiological substrate concentration, the breaks in the Arrhenius plots (critical temperature - T_c) correlated with acclimation temperatures or habitat water temperatures. Q₁₀ values for temperatures above T_c were close to one, in all cases except 4 °C acclimated trout. At temperatures below T_c Q₁₀ was close to two, except in the case of 14 °C acclimated trout. Lake trout had a highest Q₁₀ values at temperatures below T_c. It was conspicuous that within the entire range of tested temperatures the differences in Q₁₀ resulted from the effect of environmental temperature. Higher Q₁₀ values were obtained with LDH isolated from trout acclimated to 4 °C compared with LDH acclimated to 14 °C. E_a values were much lower at a temperature below T_c compared with temperatures above Tc. Thermal stability of muscle LDH was lower after acclimation to 14 compared to 4 °C, while extremely high thermostability was obtained with the lake trout enzyme. Our data support the concept that T_c values have distinct physiological significance.     

Acclimation of snow gum (Eucalyptus pauciflora) leaf respiration to seasonal and diurnal variations in temperature: the importance of changes in the capacity and temperature sensitivity of respiration

We investigated the relationship between daily and seasonal temperature variation and dark respiratory CO₂ release by leaves of snow gum (Eucalyptus pauciflora Sieb. ex Spreng) that were grown in their natural habitat or under controlled‐environment conditions. The open grassland field site in SE Australia was characterized by large seasonal and diurnal changes in air temperature. On each measurement day, leaf respiration rates in darkness were measured in situ at 2–3 h intervals over a 24 h period, with measurements being conducted at the ambient leaf temperature. The rate of respiration at a set measuring temperature (i.e. apparent ‘respiratory capacity’) was greater in seedlings grown under low average daily temperatures (i.e. acclimation occurred), both in the field and under controlled‐environment conditions. The sensitivity of leaf respiration to diurnal changes in temperature (i.e. the Q₁₀ of leaf respiration) exhibited little seasonal variation over much of the year. However, Q₁₀ values were significantly greater on cold winter days (i.e. when daily average and minimum air temperatures were below 6° and –1 °C, respectively). These differences in Q₁₀ values were not due to bias arizing from the contrasting daily temperature amplitudes in winter and summer, as the Q₁₀ of leaf respiration was constant over a wide temperature range in short‐term experiments. Due to the higher Q₁₀ values in winter, there was less difference between winter and summer leaf respiration rates measured at 5 °C than at 25 °C. The net result of these changes was that there was relatively little difference in total daily leaf respiratory CO₂ release per unit leaf dry mass in winter and summer. Under controlled‐environment conditions, acclimation of respiration to growth temperature occurred in as little as 1–3 d. Acclimation was associated with a change in the concentration of soluble sugars under controlled conditions, but not in the field. Our data suggest that acclimation in the field may be associated with the onset of cold‐induced photo‐inhibition. We conclude that cold‐acclimation of dark respiration in snow gum leaves is characterized by changes in both the temperature sensitivity and apparent ‘capacity’ of the respiratory apparatus, and that such changes will have an important impact on the carbon economy of snow gum plants.     

Influence of temperature on larval survival, development, and respiration inChasmagnathus granulata (Crustacea, Decapoda)

Larvae of an estuarine grapsid crabChasmagnathus granulata Dana 1851, from temperate and subtropical regions of South America, were reared in seawater (32/%.) at five different constant temperatures (12, 15, 18, 21, 24 °C). Complete larval development from hatching (Zoea I) to metamorphosis (Crab I) occurred in a range from 15 to 24 °C. Highest survival (60% to the first juvenile stage) was observed at 18 °C, while all larvae reared at 12 °C died before metamorphosis. The duration of development (D) decreased with increasing temperature (T). This relationship is described for all larval stages as a power function (linear regressions after logarithmic transformation of bothD andT). The temperature-dependence of the instantaneous developmental rate (D ⁻¹) is compared among larval stages and temperatures using the Q₁₀ coefficient (van't Hoff's equation). Through all four zoeal stages, this index tends to increase during development and to decrease with increasingT (comparing ranges 12–18, 15–21, 18–24 °C). In the Megalopa, low Q₁₀ values were found in the range from 15 to 24 °C. In another series of experiments, larvae were reared at constant 18 °C, and their dry weight (W) and respiratory response to changes inT were measured in all successive stages during the intermoult period (stage C) of the moulting cycle. Both individual and weight-specific respiration (R, QO ₂) increased exponentially with increasingT. At each temperature,R increased significantly during growth and development through successive larval stages. No significantly differentQO ₂ values were found in the first three zoeal stages, while a significant decrease with increasingW occurred in the Zoea IV and Megalopa. As in the temperature-dependence ofD, the respiratory response to changes in temperature (Q₁₀) depends on both the temperature range and the developmental stage, however, with different patterns. In the zoeal stages, the respiratory Q₁₀ was minimum (1.7–2.2) at low temperatures (12–18 °C), but maximum (2.2–3.0) at 18–24 °C. The Megalopa, in contrast, showed a stronger metabolic response in the lower than in the upper temperature range (Q₁₀=2.8 and 1.7, respectively). We interpret this pattern as an adaptation to a sequence of temperature conditions that should typically be encountered byC. granulata larvae during their ontogenetic migrations: hatching in and subsequent export from shallow estuarine lagoons, zoeal development in coastal marine waters, which are on average cooler, return in the Megalopa stage to warm lagoons. We thus propose that high metabolic sensitivity to changes in temperature may serve as a signal stimulating larval migration, so that the zoeae should tend to leave warm estuaries and lagoons, whereas the Megalopa should avoid remaining in the cooler marine waters and initiate its migration to wards shallow coastal lagoons.     

Ecological physiology of arctic marine invertebrates. Temperature and salinity relationships of the amphipod Onisimus affinis H. J. Hansen

Effects of temperature and salinity upon the survival, locomotion and metabolism of the Arctic marine amphipod Onisimus affinis H. J. Hansen have been investigated. The LD₅₀ for temperature is ≈ 18.7 °C. The metabolic rate-temperature curve shows a distinct plateau of relative temperature insensitivity the position of which varies seasonally to include a lower temperature range in winter than in summer. Similar shifts in the plateau can be induced in the laboratory by acclimating the animals at summer- and winter-like temperatures.Optimal locomotory activity was between 5° and 8 °C and included a combination of swimming and crawling. Above 12 °C the swimming component was increasingly inhibited.Onisimus is euryhaline and appears to be most successful in brackish water habitats. It tolerates elevated salinities better at low temperatures. The metabolic rate varies inversely with salinity during short-term exposures, but, if the animals are pre-adapted to the experimental salinities for 10 days, the metabolic rate is essentially independent of salinity between 10%. and 25%.The significance of these physiological responses in relation to the general ecology of the species is discussed.     

Geographic and seasonal patterns and limits on the adaptive response to temperature of European <Emphasis Type="Italic">Mytilus</Emphasis> spp. and <Emphasis Type="Italic">Macoma balthica</Emphasis> populations

Seasonal variations in seawater temperature require extensive metabolic acclimatization in cold-blooded organisms inhabiting the coastal waters of Europe. Given the energetic costs of acclimatization, differences in adaptive capacity to climatic conditions are to be expected among distinct populations of species that are distributed over a wide geographic range. We studied seasonal variations in the metabolic adjustments of two very common bivalve taxa at European scale. To this end we sampled 16 populations of Mytilus spp. and 10 Macoma balthica populations distributed from 39° to 69°N. The results from this large-scale comprehensive comparison demonstrated seasonal cycles in metabolic rates which were maximized during winter and springtime, and often reduced in the summer and autumn. Studying the sensitivity of metabolic rates to thermal variations, we found that a broad range of Q ₁₀ values occurred under relatively cold conditions. As habitat temperatures increased the range of Q ₁₀ narrowed, reaching a bottleneck in southern marginal populations during summer. For Mytilus spp., genetic-group-specific clines and limits on Q ₁₀ values were observed at temperatures corresponding to the maximum climatic conditions these geographic populations presently experience. Such specific limitations indicate differential thermal adaptation among these divergent groups. They may explain currently observed migrations in mussel distributions and invasions. Our results provide a practical framework for the thermal ecophysiology of bivalves, the assessment of environmental changes due to climate change and its impact on (and consequences for) aquaculture. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Thermal Acclimation of Respiration and Photosynthesis in the Marine Macroalga Gracilaria lemaneiformis (Gracilariales,Rhodophyta)

The responses of respiration and photosynthesis to temperature fluctuations in marine macroalgae have the potential to significantly affect coastal carbon fluxes and sequestration. In this study, the marine red macroalga Gracilaria lemaneiformis was cultured at three different temperatures (12, 19, and 26°C) and at high‐ and low‐nitrogen (N) availability, to investigate the acclimation potential of respiration and photosynthesis to temperature change. Measurements of respiratory and photosynthetic rates were made at five temperatures (7°C–33°C). An instantaneous change in temperature resulted in a change in the rates of respiration and photosynthesis, and the temperature sensitivities (i.e., the Q₁₀ value) for both the metabolic processes were lower in 26°C‐grown algae than 12°C‐ or 19°C‐grown algae. Both respiration and photosynthesis acclimated to long‐term changes in temperature, irrespective of the N availability under which the algae were grown; respiration displayed strong acclimation, whereas photosynthesis only exhibited a partial acclimation response to changing growth temperatures. The ratio of respiration to gross photosynthesis was higher in 12°C‐grown algae, but displayed little difference between the algae grown at 19°C and 26°C. We propose that it is unlikely that respiration in G. lemaneiformis would increase significantly with global warming, although photosynthesis would increase at moderately elevated temperatures.     

The effect of environmental factors on the absorption of amino acids by isolated gill tissue of the bivalve, Mya arenaria (L.)

The absorption of amino acids by isolated gill tissue of Mya arenaria (L.) was examined under conditions in which the environmental temperature, salinity, and pH were varied experimentally. A decrease in salinity resulted in a fall in amino-acid uptake. The V_max of L-histidine uptake increased with temperature, the Q₁₀ for the range 5° to 15 °C being 2.64. No significant effect of pH on amino-acid absorption was observed over the pH range 6.2–8.8. These results emphasize the need clearly to specify the experimental conditions when substrate uptake values are used to calculate the contribution made by any extra-alimentary absorption route to the nutritional economy of an animal.     

Temperature dependence and ontogenetic changes of metabolic rate of an endemic earthworm <Emphasis Type="Italic">Dendrobaena mrazeki</Emphasis>

Ontogenetic changes and temperature dependency of respiration rate were studied in Dendrobaena mrazeki, an earthworm species inhabiting relatively warm and dry habitats in Central Europe. D. mrazeki showed respiration rate lower than in other earthworm species, < 70 μl O₂ g⁻¹ h⁻¹, within the temperature range of 5–35°C. The difference of respiration rate between juveniles and adults was insignificant at 20°C. The response of oxygen consumption to sudden temperature changes was compared with the temperature dependence of respiratory activity in animals pre-acclimated to temperature of measurement. No significant impact of acclimation on the temperature response of oxygen consumption was found. The body mass-adjusted respiration rate increased slowly with increasing temperature from 5 to 25°C (Q₁₀ from 1.2 to 1.7) independently on acclimation history of earthworms. Oxygen consumption decreased above 25°C up to upper lethal limit (about 35°C). Temperature dependence of metabolic rate is smaller than in other earthworm species. The relationships between low metabolic sensitivity to temperature, slow locomotion and reactivity to touching as observed in this species are discussed.     

Impact of different acclimation temperatures and duration on the chill coma temperature and oxygen consumption in the tenebrionid beetle Alphitobius diaperinus

When the ambient temperature is lowered to an insect's lower thermal limit, the insect enters into chill coma. Chill coma temperature and chill coma recovery can vary within species as a result of thermal acclimation, although the physiological basis of the onset of chill coma remains poorly understood. The present study investigates how the temperature of acclimation (0, 5, 10, 15 and 20 °C for 2 or 7 days) affects chill coma temperature and oxygen consumption in adult Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae). It is hypothesized that the threshold decline in metabolic rate corresponds to the entry into chill coma. Oxygen consumption (as a proxy of metabolism) is measured across the chill coma temperature threshold, and a strong decline in oxygen consumption is expected at entry into chill coma. The acclimation decreases the chill coma temperature significantly from 6.6 ± 1.1 °C in control insects to 3.1 ± 0.7 °C in those acclimated to 10 °C. The change in metabolic rate (Q₁₀) after acclimation to temperatures ranging from 10 to 20 °C is 3.7. Despite acclimation, the metabolic rate of A. diaperinus conforms to Arrhenius kinetics, suggesting that the response of this beetle does not show metabolic compensation. The data suggest the existence of a threshold decline in metabolic rate during cooling that coincides with the temperature at which an insect goes into chill coma.