Reverse Acclimation Research Articles

Thermal acclimation of flies from three populations of Drosophila melanogaster fails to support the seasonality hypothesis

In seasonal environments, natural selection should favor genotypes that acclimate to slow and predictable changes in temperature. Selective pressure for acclimation should be especially strong for animals that complete many generations per year, because seasonal warming or cooling causes offspring to experience different temperatures than their parents did. Here, we studied variation in acclimation capacity among three populations of Drosophila melanogaster. We used a reverse acclimation design to see whether developmental acclimation persisted throughout adulthood. Flies developed from fertilization to adulthood at either 16° or 26 °C. Then, flies either remained at the same temperature or moved to the other temperature for 7 days. We measured fecundity at seven temperatures ranging from 14° to 36°C. Genotypes from North Carolina and Vermont laid more eggs at 16 °C after spending the larval and adult stages at 16 °C, instead of 26 °C. In both populations, the benefit of acclimation to 16 °C during development was erased by acclimation to 26 °C during adulthood. In contrast to our prediction, genotypes from Indiana laid fewer eggs at 16 °C or 26 °C after developing at this temperature. Overall, these data provide only weak support for the models of optimal acclimation in seasonal environments.

Phenotypic flexibility in body mass, basal metabolic rate and summit metabolism in southern red bishops (Euplectes orix): Responses to short term thermal acclimation

Avian basal metabolic rate (BMR) and summit metabolism (Msum) vary within individuals in response to seasonal acclimatization in free-ranging birds, and thermal acclimation under laboratory conditions. We examined relationships between acclimation air temperature (Tacc) and body mass (Mb), BMR and Msum in female southern red bishops (Euplectes orix) from a relatively mild coastal site and a seasonally colder, inland site. Following acclimation for 21days to Tacc=10, 22 or 35°C, Mb, BMR and Msum were all significantly and negatively related to Tacc. The significant relationship between BMR and Tacc did not remain after Mb was included as a covariate, whereas that between Msum and Tacc did. A subsequent reverse acclimation protocol, where bishops were acclimated to a second Tacc value and then re-acclimated to the first, revealed that short-term changes in Mb and BMR were completely reversible, but changes in Msum were only partially reversible. Following the reverse-acclimation protocol, metabolic expansibility (Msum/BMR) varied significantly with air temperature, being greatest at Tacc=35°C. Our data suggest that the intraspecific variation in seasonal metabolic variation previously reported for this species is at least partly driven by factors other than temperature.

Seasonal and Geographical Differences in Oxygen Consumption with Temperature ofCerastoderma glaucum(Poiret) and a Comparison withC. edule(L.)

A comparison was made of the oxygen consumption over the temperature range 5–45°C ofCerastoderma glaucum(Poiret) with season [summer (S) and winter (W)] and with latitude [Ireland (I), France (F)]. Maximum oxygen consumption rates for IW, IS, FW and FS groups were measured at 10–20°C, 20–30°C, 15–25°C and 20–35°C, respectively, reflecting the differences in the water temperatures at the time of collection of 5·5, 21·0, 6·7 and 23·5°C respectively. Upper temperature limits were estimated at between 40 and 45°C for the FS, FW and IS groups and between 35 and 40°C for the IW group. The oxygen consumption rates of both the summer groups were substantially lower than the winter rates at the same temperature, indicating a considerable degree of reverse acclimation. However the rates of the French (FW, FS) groups were lower at low temperatures, but consistently higher at high temperatures than those of the Irish (IS, IW) groups, indicating no latitudinal compensation. A major difference, that is the restriction of the Irish (IS, IW) population to one age cohort compared to at least three in the French (FS, FW) population was confirmed. Overall, the French animals, especially the smaller individuals, were slightly heavier (dry flesh weight) than their Irish counterparts.In comparison withCerastoderma edule(L.),C. glaucumhad markedly lower oxygen consumption rates at high temperatures in both summer groups, although the distinction was much less clear in the winter groups. High summer temperatures in lagoons and similar habitats could therefore be a major factor separating the distributions of the two species.

Behavioral Thermoregulation Increases Growth Rate in a Nocturnal Lizard

We tested the hypothesis that thermoregulation increases growth rate in nocturnal lizards. Leopard geckos (Eublepharis macularius) maintained from hatching at 25 C grew at a rate of 0.11 g/day, while geckos allowed to thermoregulate at preferred body temperatures (30 C for 13.5 h per day) grew 1.5 times as fast (0.16 g/day). Long-term thermal treatment had a significant reverse acclimation effect on preferred body temperature (Tp): Tp was 1.2 C lower in thermoregulatory individuals than in those kept at 25 C. Feeding and time of day also had significant but minor effects on Tp. Despite their nocturnal ecology, leopard geckos seem to be typical among lizards in requiring a diurnal heat source for maximal growth. This result provides a physiological explanation for the observation that some nocturnal lizards thermoregulate in burrows during the day, and may have implications for the biogeography of nocturnal ectotherms.

Tolerances to high temperature of infaunal bivalves and the effect of geographical distribution, position on the shore and season

There are four important influences on the temperature tolerance displayed by infaunal bivalves, namely their position on the shore, the depth to which they burrow, their geographical distribution and the seasonal cycle.The temperature tolerance of a species is closely related to shore position and burrowing depth, since these both modify the actual range of temperatures to which the organism is exposed and the tidal variation in temperature. As one might expect, southern populations of a species tend to be lower on the shore than equivalents in northern Europe, but at any one location it is difficult to detect a difference in tolerance between individuals from the top of the shore and those from the bottom. Southern populations do have a higher tolerance to high temperatures than northern, despite the shift in littoral distribution. A similar pattern of response and shift in tolerance is shown between summer- and winter-acclimated specimens.However, the seasonal shift in response to temperature is not entirely as might be expected, as oxygen consumption measurements show reverse acclimation (i.e. winter respiration rates lower than summer). Reverse acclimation has been demonstrated in a number of bivalve species, and the degree of reverse acclimation is here suggested to be related to the degree of deposit- or filter-feeding habit.There is evidence that bivalves are capable of regulating to some extent their metabolic rate, independent of temperature. Six groups of Macoma balthica were investigated, of which the four from relatively high temperature environments regulated from 20°C, while the other two did not, suggesting that this capability can be acquired.

Thermal acclimation and tolerance to lethal high temperature in the mountain stream amphipod Paramelita nigroculus (Barnard)

1. 1. Rates of upward and reverse acclimation were studied in Paramelita nigroculus (Barnard) from a mountain stream using a modification of the Critical Thermal Maximum (CTM) method. The upper lethal temperatures were measured using the LT 50 method. 2. 2. Acclimation rates were found to be typical of most crustaceans, with a gain of resistance to high temperature, following transfer from 8.5 to 20°C, being completed in 1–2 days. Loss of heat resistance took slightly longer (3 days). 3. 3. The species is strongly sexually dimorphic, males being significantly smaller than females. Neither sex, body length nor feeding status was found to affect tolerance levels. 4. 4. The LT 50 (min) for animals acclimated to 13.5°C ranged from approximately 300 min at 27°C to 4 min at 31°C. 5. 5. LT 50 values for 20°C-acclimated individuals were significantly higher than those acclimated at 13.5°C at corresponding test temperatures.

THE EFFECT OF ENVIRONMENTAL VARIABLES ON THE OXYGEN CONSUMPTION OF THE PROTOBRANCH BIVALVE NUCULA TURGIDA (LECKENBY AND MARSHALL)

The oxygen consumption of the protobranch bivalve Nucula turgida was measured in relation to size and to variation in temperature and ambient oxygen tension. The slope of the line relating log size and log oxygen uptake varied from 0.539 to 0.884 over the range 5°C to 40°C in summer – conditioned (S) animals but for winter – conditioned (W) animals the slope varied from 0.561 to 0.762 over the range 5°C to 15°C only; from 20°C to 35°C the values for the slope fell from 0.298 to 0.092. There was evidence of reverse acclimation, since the absolute rate of oxygen consumption was greater in S animals than in W over the temperature range studied. The lethal limit for both groups appeared to be between 30°C and 35°C. At all temperatures (5°C–25°C) N. turgida was found to be a near complete oxyconformer with b 2 × 10 3 values ranging from +0.0754 to −0.0234. The responses to temperature differ little from those of eulamellibranch bivalves, but the lack of ability to oxyregulate does demonstrate a difference which may be linked to the different gill structure.

Thermal acclimation in the fresh water planarians, Dugesia tigrina and D. dorotocephala

The planarians Dugesia tigrina and D. dorotocephala show well developed resistance adaptation responses following transfer from 5 to 25 °C or the reverse. Their rates of thermal acclimation are typical of most organisms, but the magnitudes of their responses are impressively large. Thermal acclimation in these two species is generally similar, although somewhat more rapid and perhaps more extensive in D. tigrina. Forward and reverse acclimation rates are similar and there is evidence of overshoot and undershoot time course patterns respectively. Our heat resistance data, although based on a different methodology (the CTM method, using loss of equilibrium as the end point criterion) agree well with published values for these triclads. The temperature tolerance and thermal acclimation responses of D. tigrina and D. dorotocephala correlate well with their apparent eurythermy and their widespread distributions.

Thermal acclimation in the crayfish, Orconectes rusticus and O. virilis

1. 1. Both Orconectes rusticus and O. virilis show a pronounced thermal acclimation response. Their heat resistance is in the upper portion of the range of literature values for crayfish and other crustaceans. 2. 2. The thermal acclimation time courses for the two species are somewhat similar. The smaller magnitude of the response for the Northern species ( O. virilis) stems from an increased heat resistance for cold acclimated animals rather than from a lowered heat resistance for 25°C acclimated crayfish. 3. 3. Two methods (CTM and LT 50) of measuring heat resistance in O. rusticus yield similar acclimation rates and time course patterns, but markedly different rates for reverse acclimation. 4. 4. Quantitative methods for acclimation time course analysis are described and applied both to the crayfish data and to derived literature values.

Some seasonal and laboratory-induced changes in the oxygen consumption of the freshwater pulmonate Lymnaea stagnalis (L.)

1. 1.|The slope of the common regression line relating size and oxygen consumption in Lymnaea stagnalis (L.) changes with exposure temperature and with season, but is not apparently affected by acclimation to different constant temperatures. 2. 2.|Oxygen consumption is generally higher in summer than in winter when measured at the same exposure temperature. This indicates an apparent reverse acclimation in response to seasonal changes in environmental temperature. Acclimation to constant temperature in the laboratory however, does not induce such changes, suggesting that the apparent reverse acclimation response is not a direct temperature effect. 3. 3.|Both the seasonal and laboratory studies show complex changes in the form of the oxygen consumption rate-temperature curves, with areas of reduced temperature sensitivity often apparent. 4. 4.|Possible factors responsible for the observed seasonal changes are discussed.

RESPIRATORY VARIATION AND ACCLIMATION IN THE FRESHWATER LIMPET,LAEVAPEX FUSCUS

1. From three populations of Laevapex fuscus samples were collected bi-weekly through 1970 to 1972. Oxygen consumption rates at ambient temperature and at 10° C and at 20° C were determined. Other respiration experiments involved decreasing O2 tension at 20° C and the consequences of low oxygen stress.2. At ambient temperatures, respiration during the summer is normally 26 to 36 times the winter respiratory rate.3. After treatment with low oxygen stress there is no overt payment of an oxygen debt in Laevapex, instead there is a general increase in respiratory rate at all oxygen tensions. These rates are maintained for up to 135 hours after return to fully saturated conditions and appear to be in part a short-term acclimation of respiratory rates to low oxygen tensions.4. Measured at 100% oxygen tension at 10° and 20° C, respiration rates are higher in the summer than in the winter for all three populations. Such a respiratory response to temperature has been called reverse acclimation. Laevapex lives in conditions of low oxygen tension during the winter. The respiration experiments with decreasing oxygen tension show that at low oxygen tensions winter-conditioned specimens have a higher respiratory rate than summer-conditioned individuals. Such a response to low oxygen tensions may be interpreted as a positive rather than reverse acclimation.5. A hypothesis is advanced regarding "reverse" acclimation in this species. Reverse acclimation appears to be merely one manifestation of a more general acclimatory change in winter-conditioned Laevapex. These limpets, when winter-conditioned, have a higher respiratory rate at low oxygen tension than do summer-conditioned limpets. Although this acclimatory process appears to be triggered by decreasing temperature, its adaptational significance involves the survival of the inactive overwintering limpet in contact with reducing mud.

Biomass Turnover, Respiration, and Interpopulation Variation in the Stream Limpet Ferrissia rivularis (Say)

The stream limpet Ferrissia rivularis, which occurs extensively in North America and is ubiquitous in streams of upper New York State, was studied from two distinct populations, one located in the Canandaigua Outlet at Alloway, N. Y. (AL) and the other in Black Creek at Cleveland, N. Y. (BC). These environments differ substantially, that at AL being the more eutrophic. At BC there is one generation per year, but at AL there are two generations per year and more rapid growth rates. Thirteen months is the adult life span for BC limpets, whereas at AL 11 and 3 months are normal for spring and summer adults respectively. At BC 8.4 eggs per limpet are laid, and 34.8 eggs per limpet are laid by spring adults at AL. Biomass and egg production are assessed as total carbon (equivalent to calorific measures) and expressed as biomass—turnover rates (growth and egg production). Egg—production rates can be double those for growth at AL; at BC egg—production rates are usually less than those for growth. This is partly a consequence of greater primary productivity at AL, but may also reflect implied genetic differences. Limpets at BC build up carbon during late summer and early fall; an increase in the C:N ratio (to 4.8) indicates an accumulation of storage compounds. During the winter (lower temperature, solar input, and primary productivity) the C:N ratio decreases, and during spring breeding there is a more marked loss of carbon associated with egg laying. In field—acclimated BC animals, respiration is lowest during the winter; during the spring, respiratory rate is closely correlated with temperature and egg—laying intensity. Oxygen—consumption measurements at 10° and 20°C for all seasons reveal that these limpets show reverse acclimation at low temperature (qualitative and quantitative downward adjustment of metabolism). This acclimation pattern is accompanied by a decrease in Q10 (3.3 to 2.1) which can act to dampen the effects of winter temperature fluctuations. Energy balance (respiration, growth, egg production) is expressed as rates of carbon turnover for the population at BC. Respiration rates are greatest during the summer and spring and reflect increased assimilation due to growth or reproduction or both. The total carbon turnover per year is approximately 1.25 g/m2. Data on energy balance emphasize the adaptive importance of reverse acclimation at times of low energy input.