The effect of temperature on juvenile Mozambique tilapia hybrids (Oreochromis mossambicus x O. urolepis hornorum) exposed to full-strength and hypersaline seawater

The effects of temperature on the salinity tolerance of Mozambique-Wami tilapia hybrids (Oreochromis mossambicus x O. urolepis hornorum) were investigated by transferring 35 g/l, 25 degrees C-acclimated fish to 35, 43, 51 or 60 g/l salinity at 15, 25 or 35 degrees C for 24 h, and by assaying gill tissue for branchial Na(+), K(+)-ATPase activity at the three temperatures after acclimating the fish to 15, 25 or 35 degrees C for 2 weeks. Tilapia survived all salinities at 25 and 35 degrees C; however, at 15 degrees C, mortality was 85.7% and 100% in the 51 g/l and 60 g/l groups, respectively. There was a significant interaction between temperature and salinity, as plasma osmolality, [Na(+)] and [Cl(-)] were significantly increased at 51 and 60 g/l salinity in 35 degrees C water (P<0.001). Additionally, muscle water content was significantly reduced at 43 g/l, 15 degrees C relative to pre-transfer values (P<0.001). Branchial Na(+), K(+)-ATPase activity was reduced at 15 degrees C regardless of acclimation temperature, and 25 degrees C-acclimated gill tissue did not show an increase in activity when assayed at 35 degrees C. Results indicate that the effects of a combined temperature-salinity transfer on plasma osmolality and ion concentrations, as well as muscle water content, are greater than when either challenge is given alone. Additionally, branchial Na(+), K(+)-ATPase activity is altered when assayed at varying temperatures; in the case of 15 degrees C, regardless of acclimation temperature. Our enzyme activity data may indicate the presence of a high temperature isoform of branchial Na(+), K(+)-ATPase enzyme.     

Cold acclimation strategy is highly variable among the sunfishes (Centrarchidae)

We tested the hypothesis that the physiological strategy for acclimating to low body temperature is similar among closely related fish. Largemouth bass (Micropterus salmoides), green sunfish (Lepomis cyanellus), bluegill sunfish (Lepomis macrochirus), black crappie (Pomonix nigromaculatus), and white crappie (Pomonix annularis), all members of the family Centrarchidae, were acclimated to 5 degrees and 25 degrees C. Morphometric variables (total mass, total length, organ masses) and enzyme activities (hexokinase; lactate dehydrogenase; and cytochrome oxidase in heart, liver, and muscle) were measured in 5 degrees C- and 25 degrees C-acclimated fish at 5 degrees and 25 degrees C assay temperatures. Each species displayed a distinct physiological response to cold acclimation that differed among tissues. These data suggest that the response to cold acclimation is highly variable within families. Our findings are consistent with other studies suggesting that acclimation responses are labile and may evolve independently even among closely related species.     

Strong Costs and Benefits of Winter Acclimatization in Drosophila melanogaster

Studies on thermal acclimation in insects are often performed on animals acclimated in the laboratory under conditions that are not ecologically relevant. Costs and benefits of acclimation responses under such conditions may not reflect costs and benefits in natural populations subjected to daily and seasonal temperature fluctuations. Here we estimated costs and benefits in thermal tolerance limits in relation to winter acclimatization of Drosophila melanogaster. We sampled flies from a natural habitat during winter in Denmark (field flies) and compared heat and cold tolerance of these to that of flies collected from the same natural population, but acclimated to 25 °C or 13 °C in the laboratory (laboratory flies). We further obtained thermal performance curves for egg-to-adult viability of field and laboratory (25 °C) flies, to estimate possible cross-generational effects of acclimation. We found much higher cold tolerance and a lowered heat tolerance in field flies compared to laboratory flies reared at 25 °C. Flies reared in the laboratory at 13 °C exhibited the same thermal cost-benefit relations as the winter acclimatized flies. We also found a cost of winter acclimatization in terms of decreased egg-to-adult viability at high temperatures of eggs laid by winter acclimatized flies. Based on our findings we suggest that winter acclimatization in nature can induce strong benefits in terms of increased cold tolerance. These benefits can be reproduced in the laboratory under ecologically relevant rearing and testing conditions, and should be incorporated in species distribution modelling. Winter acclimatization also leads to decreased heat tolerance. This may create a mismatch between acclimation responses and the thermal environment, e.g. if temperatures suddenly increase during spring, under current and expected more variable future climatic conditions.     

Plasticity of myosin heavy chain expression with temperature acclimation is gradually acquired during ontogeny in the common carp (Cyprinus carpio L.)

Common carp (Cyprinus carpio L.) were reared from hatching until 61 mm total length (TL) at 21 degrees C. At 14 weeks and 20 weeks post-hatch, corresponding to initial lengths of 30 mm and 44 mm respectively, fish were acclimated to 10 degrees C using a rate of cooling of 1 degrees C per day. A statistical model was used to compare the time course in the change of white muscle myofibrillar ATPase activity with temperature acclimation. The myosin heavy chain (MHC) composition of white muscle myofibrils was investigated using peptide mapping. A significant increase in myofibrillar ATPase activity was observed after 2-3 weeks in the 44 mm group, but not until 4-5 weeks in the 30 mm group. when they had reached 37 mm TL. The MHC banding pattern of 120 mm TL fish acclimated to 10 degrees C or 21 degrees C for a minimum of 6 weeks were distinct from each other. The MHC peptide map characteristic of 10-degrees C-acclimated fish was not observed in individuals less than 37 mm length. We therefore conclude that the capacity to alter the composition and properties of myofibrils with cold acclimation is acquired in juvenile carp at around 37 mm TL.     

Effects of acclimation temperature on membrane phospholipids in the flesh fly Sarcophaga similis

Cold acclimation is a well‐known strategy for enhancing cold tolerance in ectotherms including insects. Nevertheless, information on the physiological mechanisms underpinning this phenomenon is still limited. Biological membrane integrity is critical for insects to perform at low temperatures, and an advantage is conferred on those insects that can adjust the composition of their membrane phospholipids. Such changes contribute to homeoviscous adaptation, a process that allows membranes to maintain a liquid–crystalline (fluid) state at low temperatures. Here we investigated phospholipids in the flesh fly Sarcophaga similis acclimated to various temperatures. Significant differences were observed in the composition of their fatty acyl chains: flies acclimated to low temperatures showed a higher proportion of palmitic and oleic acids at the expense of palmitoleic acid. Other fatty acids (stearic, linoleic, linolenic, arachidonic, eicosapentaenoic acids) were not significantly changed. The degree of unsaturation decreased in cold‐acclimated flies, but the difference was quite small. The weighted average chain length and number of double bonds were unchanged among flies acclimated to different temperatures. As temperatures decreased, the percentage of phosphatidylethanolamine increased to twice that of phosphatidylcholine. We discuss the role of these phospholipid changes in cold acclimation.     

Is fluid-phase endocytosis conserved in hepatocytes of species acclimated and adapted to different temperatures?

Our primary objective was to determine if rates of fluid-phase endocytosis (FPE) were conserved in hepatocytes from organisms acclimated and adapted to different temperatures. To this aim, the fluorescent dye Lucifer yellow was employed to measure FPE at different assay temperatures (AT) in hepatocytes from 5 degrees C- and 20 degrees C-acclimated trout, Oncorhynchus mykiss (at 5 and 20 degrees C AT), 22 degrees C- and 35 degrees C-acclimated tilapia, Oreochromis nilotica (at 22 and 35 degrees C AT), and the Sprague-Dawley rat (at 10, 20, and 37 degrees C AT). FPE was also studied in rats fed a long-chain polyunsaturated fatty acid (PUFA)-enriched diet (at 10 degrees C AT). Despite being temperature dependent, endocytic rates (values in pl. cell(-1). h(-1)) in both species of fish were compensated after a period of acclimation. For example, in 20 degrees C-acclimated trout, the rate of endocytosis declined from 1.84 to 1.07 when the AT was reduced from 20 to 5 degrees C; however, after a period of acclimation at 5 degrees C, the rate (at 5 degrees C AT) was largely restored (1.80) and almost perfectly compensated (95%). In tilapia, endocytic rates were also temperature compensated, although only partially (36%). Relatively similar rates obtained at 5 degrees C in 5 degrees C-acclimated trout (1.8), at 20 degrees C in 20 degrees C-acclimated trout (1.84), and at 22 degrees C in 22 degrees C-acclimated tilapia (2.2) suggest that endocytic rates are somewhat conserved in these two species of fish. In contrast, the rate in rat measured at 37 degrees C (16.83) was severalfold greater than in fish at their respective body temperatures. A role for lipids in determining rates of endocytosis was supported by data obtained at 10 degrees C in hepatocytes isolated from rats fed a long-chain PUFA-enriched diet: endocytic rates were higher (5.35 pl. cell(-1). h(-1)) than those of rats fed a standard chow diet (2.33 pl. cell(-1). h(-1)). The conservation of endocytic rates in fish may be related to their ability to conserve other membrane characteristics (i.e., order or phase behavior) by restructuring their membrane lipid composition or by modulating the activities of proteins that regulate endocytosis and membrane traffic, whereas the lack of conservation between fish and rat may be due to differences in metabolic rate.     

General introduction to the lists of threatened biotopes,flora and fauna of the trilateral Wadden Sea Area (red data book)

The effect of the acclimation temperature on the temperature tolerance ofPorphyra leucosticta, and on the temperature requirements for growth and survival ofEnteromorpha linza was determined under laboratory conditions. Thalli ofP. leucosticta (blade or Conchocelis phases), acclimated to twenty-five degrees, survived up to 30°C, i.e. 2°C more than those acclimated to 15°C which survived up to 28°C. Lower temperature tolerance of bothPorphyra phases that were acclimated to 15°C was −1°C after an 8-week exposure time at the experimental temperatures. The upper temperature tolerance ofE. linza also increased by 2°C, i.e. from 31 to 33°C, when it was acclimated to 30°C instead of 15°C. The lower temperature tolerance increased from 1 to −1°C, when it was acclimated to 5°C instead of 15°C.E. linza thalli acclimated for 4 weeks to 5 or 10°C reached their maximum growth at 15°C, i.e. at a 5°C lower temperature than those acclimated to 15 or 30°C. These thalli achieved higher growth rates in percent of maximal growth at low temperatures than those acclimated to 15 or 30°C. Thalli acclimated for 1 week to 5°C reached their maximum growth rate at 20°C and achieved growth rates at low temperatures similar to those recorded for thalli acclimated to 15°C. Thalli ofE. linza acclimated for 4 weeks to 5°C lost this acclimation after being post-cultivated for the same period at 15°C. That was not the case with thalli acclimated for 8 weeks to 5°C and post-acclimated for 4 weeks to 15°C. These thalli displayed similar growth patterns at 10–25°C, while a decline of growth rate was observed at 5 or 30°C. The significance of the acclimation potential ofE. linza with regard to its seasonality in the Gulf of Thessaloniki, and its distribution in the N Atlantic, is also discussed.     

The effect of cold acclimation and deacclimation on cold tolerance,trehalose and free amino acid levels in Sitophilus granarius and Cryptolestes ferrugineus (Coleoptera)

Canadian and French laboratory strains of Sitophilus granarius (L.) and Cryptolestes ferrugineus (Stephens) were cold acclimated by placing adults at 15, 10 and 5 degrees C successively for 2wk at each temperature before deacclimating them for 1wk at 30 degrees C. Unacclimated S. granarius had an LT(50) (lethal time for 50% of the population) of 12days at 0 degrees C compared with 40days after the full cold acclimation. At -10 degrees C, unacclimated C. ferrugineus had an LT(50) of 1.4days compared with 24days after the full acclimation. Cold acclimation was lost within a week after returning insects to 30 degrees C. Trehalose, as well as the amino acids proline, asparagine, glutamic acid and lysine were higher in cold acclimated insects for both species. For S. granarius, glutamine was higher in cold acclimated insects and isoleucine, ethanolamine and phosphoethanolamine, a precursor of phospholipids, were lower in cold acclimated insects. For C. ferrugineus, alanine, aspartic acid, threonine, valine, isoleucine, leucine, phenylalanine and phosphoethanolamine were higher in cold acclimated insects. For both species tyrosine was lower in cold acclimated insects. There were small but significant differences between Canadian and French strains of S. granarius, with the Canadian strain being more cold hardy and having higher levels of trehalose. There were small but significant differences between male and female S. granarius, with males being more cold hardy and having higher levels of proline, asparagine and glutamic acid. In conclusion, high levels of trehalose and proline were correlated with cold tolerance, as seen in several other insects. However, correlation does not prove that these compounds are responsible for cold tolerance, and we outline further tests that could demonstrate a causal relationship between trehalose and proline and cold tolerance.     

The mean and variance of environmental temperature interact to determine physiological tolerance and fitness

Global climate change poses one of the greatest threats to biodiversity. Most analyses of the potential biological impacts have focused on changes in mean temperature, but changes in thermal variance will also impact organisms and populations. We assessed the combined effects of the mean and variance of temperature on thermal tolerances, organismal survival, and population growth in Drosophila melanogaster. Because the performance of ectotherms relates nonlinearly to temperature, we predicted that responses to thermal variation (±0° or ±5°C) would depend on the mean temperature (17° or 24°C). Consistent with our prediction, thermal variation enhanced the rate of population growth (r(max)) at a low mean temperature but depressed this rate at a high mean temperature. The interactive effect on fitness occurred despite the fact that flies improved their heat and cold tolerances through acclimation to thermal conditions. Flies exposed to a high mean and a high variance of temperature recovered from heat coma faster and survived heat exposure better than did flies that developed at other conditions. Relatively high survival following heat exposure was associated with low survival following cold exposure. Recovery from chill coma was affected primarily by the mean temperature; flies acclimated to a low mean temperature recovered much faster than did flies acclimated to a high mean temperature. To develop more realistic predictions about the biological impacts of climate change, one must consider the interactions between the mean environmental temperature and the variance of environmental temperature.     

Complexity of the cold acclimation response in Drosophila melanogaster

Insects can increase their resistance to cold stress when they are exposed to non-lethal conditions prior to the stress; these plastic responses are normally described only in terms of immediate effects on mortality. Here we examine in Drosophila melanogaster the short- and longer-term effects of different conditions on several measures of cold resistance, but particularly chill coma recovery. Short-term exposure to sublethal temperature (cold hardening) did not decrease chill coma recovery times even though it decreased mortality. Exposure to 12 degrees C for 2 days (acclimation) decreased chill coma recovery times for a range of stressful temperatures when flies were cultured at 25 degrees C, but did not usually affect recovery times when flies were cultured at 19 degrees C. In contrast, 2-day exposure to 12 degrees C decreased mortality regardless of rearing temperature. Rearing at 19 degrees C decreased mortality and chill coma recovery time relative to rearing at 25 degrees C. Acclimation increased the eclosion rate of eggs from stressed females, but did not affect development time or size of the offspring. These results indicate that plastic responses to cold in D. melanogaster are complex when resistance is scored in different ways, and that effects can extend across generations.     

Acclimation of entomopathogenic nematodes to novel temperatures: trehalose accumulation and the acquisition of thermotolerance

The effect of thermal acclimation on trehalose accumulation and the acquisition of thermotolerance was studied in three species of entomopathogenic nematodes adapted to either cold or warm temperatures. All three Steinernema species accumulated trehalose when acclimated at either 5 or 35 degrees C, but the amount of trehalose accumulation differed by species and temperature. The trehalose content of the cold adapted Steinernema feltiae increased by 350 and 182%, of intermediate Steinernema carpocapsae by 146 and 122% and of warm adapted Steinernema riobrave by 30 and 87% over the initial level (18.25, 27.24 and 23.97 microg trehalose/mg dry weight, respectively) during acclimation at 5 and 35 degrees C, respectively. Warm and cold acclimation enhanced heat (40 degrees C for 8h) and freezing (-20 degrees C for 4h) tolerance of S. carpocapsae and the enhanced tolerance was positively correlated with the increased trehalose levels. Warm and cold acclimation also enhanced heat but not freezing tolerance of S. feltiae and the enhanced heat tolerance was positively correlated with the increased trehalose levels. In contrast, warm and cold acclimation enhanced the freezing but not heat tolerance of S. riobrave, and increased freezing tolerance of only warm acclimated S. riobrave was positively correlated with the increased trehalose levels. The effect of acclimation on maintenance of original virulence by either heat or freeze stressed nematodes against the wax moth Galleria mellonella larvae was temperature dependent and differed among species. During freezing stress, both cold and warm acclimated S. carpocapsae (84%) and during heat stress, only warm acclimated S. carpocapsae (95%) maintained significantly higher original virulence than the non-acclimated (36 and 47%, respectively) nematodes. Both cold and warm acclimated S. feltiae maintained significantly higher original virulence (69%) than the non-acclimated S. feltiae (0%) during heat but not freezing stress. In contrast, both warm and cold acclimated S. riobrave maintained significantly higher virulence (41%) than the non-acclimated (14%) nematodes during freezing, but not during heat stress. Our data indicate that trehalose accumulation is not only a cold associated phenomenon but is a general response of nematodes to thermal stress. However, the extent of enhanced thermal stress tolerance conferred by the accumulated trehalose differs with nematode species.     

Investigating thermal acclimation effects before and after a cold shock in Drosophila melanogaster using behavioural assays

Acclimation to environmental change can impose both costs and benefits to organisms. In this study we explored to what extent locomotor behaviour of Drosophila melanogaster is influenced by developmental temperature and adult temperature in both the laboratory and the field. Following development at 15, 25, or 31 °C, adult flies were tested for locomotor activity at all developmental temperatures in the laboratory before and after exposure to a cold shock and in the field for their ability to locate resources after a cold shock. Both test (15, 25, and 31 °C) and developmental temperatures strongly affected locomoter activity, with flies developed at 25 °C having the highest activity at all three test temperatures before the cold shock. After the cold shock flies developed at 15 °C had higher activity compared with flies developed at 25 and 31 °C when tested at 15 and 25 °C, and flies developed at 25 °C had the highest activity when tested at 31 °C. Furthermore, flies developed at 31 °C showed longer recovery times following the cold shock at test temperatures of 15 and 25 °C. However, flies acclimated at 15 °C during development did not recover faster at 15 and 25 °C compared with flies developed at 25 °C. There were no significant correlations between recovery time and locomotor activity at any of the test temperatures. Flies developed at 15 °C and exposed to a cold shock before release in the field were much more successful in locating a resource at low field temperatures compared with flies developed at 25 and 31 °C. Our results provide support for both the beneficial acclimation hypothesis and the optimal developmental temperature hypothesis, but the results are highly context dependent and change with the temperature experienced by the individual during its lifetime.     

The effects of acclimation on thermal tolerance, desiccation resistance and metabolic rate in Chirodica chalcoptera (Coleoptera: Chrysomelidae)

Despite much focus on species responses to environmental variation through space and time, many higher taxa and geographic areas remain poorly studied. We report the effects of temperature acclimation on thermal tolerance, desiccation rate and metabolic rate for adult Chirodica chalcoptera (Coleoptera: Chrysomelidae) collected from Protea nerifolia inflorescences in the Fynbos Biome in South Africa. After 7 days of acclimation at 12, 19 and 25 degrees C, critical thermal maxima (mean+/-s.e.: 41.8+/-0.2 degrees C in field-fresh beetles) showed less response (<1 degrees C change) to temperature acclimation than did the onset of the critical thermal minima (0.1+/-0.2, 1.0+/-0.2 and 2.3+/-0.2 degrees C, respectively). Freezing was lethal in C. chalcoptera (field-fresh SCP -14.6 degrees C) and these beetles also showed pre-freeze mortality. Survival of 2 h at -10.1 degrees C increased from 20% to 76% after a 2 h pre-exposure to -2 degrees C, indicating rapid cold hardening. Metabolic rate, measured at 25 degrees C and adjusted by ANCOVA for mass variation, did not differ between males and females (2.772+/-0.471 and 2.517+/-0.560 ml CO2 h(-1), respectively), but was higher in 25 degrees C-acclimated beetles relative to the field-fresh and 12 degrees C-acclimated beetles. Body water content and desiccation rate did not differ between males and females and did not respond significantly to acclimation. We place these data in the context of measured inflorescence and ambient temperatures, and predict that climate change for the region could have effects on this species, in turn possibly affecting local ecosystem functioning.     

Locomotor performance of Drosophila melanogaster: interactions among developmental and adult temperatures, age, and geography

We explored the extent to which a phenotypic trait (walking speed) of Drosophila melanogaster is influenced by population, developmental temperature, adult temperature, and age. Our goals were to estimate the importance of these factors and to test the beneficial acclimation hypothesis. We measured speed of flies from two populations (the Congo and France) that developed at different temperatures (18, 25, and 29 degrees C) and were tested at different temperatures (18, 25, and 29 degrees C) and ages (2, 7, 13 days). Not surprisingly, speed increased strongly with test temperature. Speed was generally greatest for flies reared at an intermediate developmental temperature, contrary to the beneficial acclimation hypothesis, which predicts that speed would be greatest when influenced by interactions involving population. For example, speed was greatest for flies from France that developed at a low temperature, but for flies from the Congo that developed at a high temperature. The impact of developmental temperature declined with age. Surprisingly, speed actually increased with age for flies raised and maintained at a low temperature, but decreased with age for flies raised and maintained at an intermediate or at a high temperature. Thus, walking performance is highly dynamic phenotypically, complicating potential attempts to predict responses to selection on performance.     

Cold tolerance in Drosophila: adaptive variations revealed by the analysis of starvation survival reaction norms

Three species of Drosophila were investigated for their capacity to survive without food (starvation tolerance) at seven different temperatures ranging from 0 to 25 degrees C. In all cases biphasic response curves (reaction norms) were observed, corresponding either to special deleterious effects of cold or to a progressive exhaustion of reserves proportional to metabolic rate. The temperature at which survival was longest was called the threshold temperature. The position of the threshold exhibited adaptive changes, either due to acclimation in the same species, or to genetic variations evidenced between species. In D. melanogaster, adults grown at lower temperature (12 degrees C) were more tolerant to cold than adults grown at higher temperatures (21, 25 or 30 degrees C). This acclimation process shifted, in an adaptive way, the position of the threshold temperature from 6.2 to 7.5 degrees C. A comparison of three different species grown at a single developmental temperature (21 degrees C) revealed similar but greater adaptive differences in their threshold temperature: 4.8 degrees C in the temperate D. subobscura, 7 degrees C in the cosmopolitan D. melanogaster and 14.6 degrees C in the tropical D. ananassae.     

Changes in membrane lipid composition following rapid cold hardening in Drosophila melanogaster

Naturally occurring diurnal variations in temperature are sufficient to induce a rapid cold hardening (RCH) response in insects. RCH can increase cold tolerance by 1-2 degrees C and extend the temperature interval at which insects can remain active. While the benefits of RCH are well established, the underlying physiological mechanisms remain unresolved. In this study we investigated the role of RCH on expression of heat shock proteins (Hsp70) after a cold shock, and the effect of RCH on the composition of phospholipid fatty acids (PLFAs) in membranes of Drosophila melanogaster. These experiments were performed on both "control" flies and flies selected for cold resistance in order to additionally examine a possible target for selection for cold tolerance. RCH improved survival following cold shock at -4, -6 and -8 degrees C. No induction of Hsp70 was found following cold shock irrespective of the pre-treatment. In contrast, a 5h RCH treatment was sufficient to induce small, but significant, changes in the composition of PLFAs. Here, the polyunsaturated linoleic acid, 18:2(n-6), increased while monounsaturated (18:1) and saturated (14:0) PLFAs decreased in abundance. These changes were observed in both selection groups and caused a significant increase in the overall degree of unsaturation. This response is consistent with the membrane response typically found during cold acclimation in ectothermic animals and it is likely adaptive to maintain membrane function during cold. Cold selection resulted in PLFA changes (decrease of 18:0 and 18:1 and increase of 14:0 and 16:1), which may improve the ability to harden during RCH.     

Temperature acclimation and the expression of contractile protein isoforms in the skeletal muscles of the common carp (Cyprinus carpio L.)

Summary Common carp (Cyprinus carpio L.) were acclimated to either 2, 5, 8, 11, 15, 20, or 23°C for 12 weeks (12 h light: 12 h dark). Fish did not feed after 6 weeks at temperatures below 8°C. Skinned fibres were prepared from fast myotomal muscle by freeze-drying. Measured at 0°C unloaded contraction velocity (Vmax) and maximum isometric tension generation (Po) were 2–3 times higher in the 11°C-than 23°C-acclimated groups, and had intermediate values in 15 °C-acclimated fish. Po and Vmax at 0°C were not significantly different for carp maintained at 2, 5, 8, or 11°C. Measured at the acclimation temperature of each group Vmax and Po were 51% and 71% lower for fibres from 2°C- than 23°C-acclimated fish. The results indicate a partial capacity adaptation of muscle power output in fish acclimated between 11°C and 23°C. At 8°C the ATPase activity of myofibrils was 2 times higher in fish acclimated to 8°C than to 20°C. The effects of temperature acclimation on the protein composition of myofibrils was investigated using one- and two-dimensional electrophoresis. Peptide maps of purified myosin heavy chains and actin prepared by proteolytic digestion with either Staphylococcus aureus V8 protease or chymotrypsin were similar for both acclimation groups. The molecular weights and isoelectric points of the major isoforms of tropomyosin, troponin C, troponin I, troponin T, and myosin light chains (MLC1, MLC2 and MLC3) were also similar in 8°C- and 20°C-acclimated carp. A 20 kDa molecular weight protein with a pI intermediate between that for MLC2 and MLC3 was found in myofibrils and single fibres from carp acclimated to 8°C but was not present in carp acclimated to 20°C. It is suggested that this band corresponds to a myosin light chain isoform unique to cold-acclimated fish. Evidence was also obtained that myofibrils from warm-acclimated fish contained a second minor isoform of troponin I.     

Effects of acclimation temperature on enzymatic capacities and mitochondrial membranes from the body wall of the earthworm Lumbricus terrestris

Many ectotherms respond to low temperature by adjusting capacities of enzymes from energy metabolism, restructuring membrane phospholipids and modulating membrane fluidity. Although much is known about the temperature biology of earthworms, it is not known to what extent earthworms employ compensatory changes in enzymatic capacities and membrane physical properties after exposure to low temperature. We examined activities of enzymes from glycolysis and central oxidative pathways as well as fluidity and phospholipid fatty acid composition of mitochondrial membranes prepared from the body wall of the temperate oligochaete Lumbricus terrestris after a one month acclimation to 5 degrees and 15 degrees C. No compensation occurs in central pathways of oxidative metabolism since activities of cytochrome-c oxidase and citrate synthase, when measured at a common temperature, are similar for 5 degrees C and 15 degrees C-acclimated animals. In contrast, activity of pyruvate kinase is elevated 1.3-fold after acclimation to 5 degrees C. Mitochondrial membranes display inverse compensation with respect to temperature (membranes from 5 degrees C animals are more ordered than membranes from 15 degrees C animals). Our results, in combination with earlier reports, indicate that routine metabolism in L. terrestris may be maintained at reduced temperatures with little or no change in enzymatic capacities and inverse compensation of mitochondrial membranes.     

Effects of acclimation and egg-incubation temperature on selected temperature by hatchling western painted turtles (Chrysemys picta bellii)

The ability of hatchling turtles to detect environmental temperature differences and to effectively select preferred temperature is a function that critically impacts survival. In some turtle species, temperature preference may be influenced by embryonic and post-hatching conditions, such as egg-incubation and acclimation temperature. We tested for effects of embryonic incubation temperature (27.5 °C, 30 °C) and acclimation temperature (20 °C, 25 °C) on the selected temperature and movement patterns of 32 Chrysemys picta bellii (Reptilia: Emydidae) hatchlings in an aquatic thermal gradient of 14-34 °C and in single-temperature (20 °C, 25 °C) control tests. Among 10-11 month old hatchlings, acclimation temperature and egg-incubation temperature influenced temperature selection and movement patterns. Acclimation temperature affected activity and movement: in thermal gradient and single-temperature control tests, 25 °C-acclimated turtles relocated between chambers significantly more frequently than individuals acclimated to 20 °C. Acclimation temperature also affected temperature selection: 20 °C-acclimated turtles selected a specific temperature during gradient tests, but 25 °C-acclimated turtles did not. Among 20 °C-acclimated turtles, egg-incubation temperature was inversely related to selected temperature: hatchling turtles incubated at 27.5 °C selected the warmest temperature available (34 °C); individuals incubated at 30 °C selected the coldest temperature (14 °C). These results suggest that interactions of environmental conditions may influence post-hatching thermoregulatory behavior in C. picta bellii, a factor that ultimately affects fitness.