Modelling development time of Lipaphis erysimi (Hemiptera: Aphididae) at constant and variable temperatures

The development period from birth to adult of virginoparae of the turnip aphid, Lipaphis erysimi (Kaltenbach), at 14 constant, 15 alternating and 15 natural temperature regimes were modelled to determine mathematical functions for simulating aphid development under a wide range of natural conditions. The day-degree model, the logistic equation, and the Wang model were used to describe the relationships between temperature and development rate at constant and alternating temperatures. The three models were then used with a Weibull function describing the distribution of development times, to simulate the development of individuals of cohorts at natural temperature regimes. Comparison of the observed with simulated distributions of adult emergence indicates that all three models can simulate the development of L. erysimi equally well when temperature does not go below 6 degrees C (the notional low temperature threshold of the day-degree model) or above 30 degrees C. When accumulation of temperatures below 6 degrees C becomes substantial, only the logistic curve offers accurate simulations; the other two models give falsely longer durations of development. When accumulation of temperatures above 30 degrees C becomes substantial, the logistic curve and the Wang model offer more accurate simulations than the day-degree model, which tends to produce shorter durations of development. Further analysis of the data reveals that development rate of this aphid at a given unfavourable high temperature may vary with time. Methods for accurately simulating the development time of L. erysimi in the field are suggested. The significance of modelling insect development at low and high temperatures by non-linear models is discussed.     

Effects of temperature on the development,growth, and survival of larvae and pupae of a north-temperate chrysomelid beetle

Summary Developoment, growth, and survival of larvae and pupae of the red turnip beetle, Entomoscelis americana Brown, were studied in 10 constant and four alternating temperature regimes (10 to 32.5° C), in field-cages, and in natural populations in Manitoba. This beetle has a northtemperate distribution in North America. Larval and pupal development occurs in spring and normally is completed before the end of June. Growth and development occurred at all constant temperatures tested, but survival was low at the extreme temperatures. Therefore, the threshold and upper limit were near 10 and 32.5° C. The developmental times of the sexes did not differ and decreased with temperature, except possibly at 32.5° C. The average weight of adult females increased with temperature up to 32.5° C and those of males up to 25° C. Considering developmental rate, survival, adult weight, and incidence of malformed adults, the optimum temperature was estimated to be near 27.5° C.Development was accelerated significantly (6 to 9%) in alternating regimes with temperatures differing by 10° C, but not in regimes differing by 5 and 15° C. All alternating regimes increased adult weight, 5 to 17% for females and 2 to 10% for males. Field cage studies confirmed the increase in adult weight, but not the acceleration in development.A three-parameter normal function described accurately the relationship between developmental rate and constant temperature. A computer simulation model based on this equation estimated developmental times in field cages to within one to five days. For natural populations the model overestimated the developmental times by five to 16 days. The discrepancies between model estimates and observed developmental times in natural populations apparently were due to the elevation of larval and pupal body temperatures above air temperatures by behavioral thermoregulation. The elevation of body temperature was estimated to be equivalent to the addition of 5 to 6° C to the maximum daily air temperature. The adaptations and responses of this beetle to the cool spring temperatures of the north-temperate region are discussed.Contribution No. 1164, Agriculture Canada, Research Station, Winnipeg, Manitoba, Canada     

How a thermal dichotomy in nesting environments influences offspring of the world's most northerly oviparous snake,Natrix natrix (Colubridae)

Temperature has a major influence on the rate of embryonic development in ectothermic organisms. While incubation experiments unambiguously show that constant high temperature accelerates development and shortens embryonic life, studies on the effect of fluctuating temperatures have generated contradictory results. Grass snakes (Natrix natrix) occur at latitudes and altitudes that are unusually cool for an oviparous reptile. In these cool climates females typically lay their eggs in heat‐generating anthropogenic microhabitats that provide either a highly fluctuating (compost piles) or a relatively constant (manure heaps) thermal nesting environment. A laboratory experiment with fluctuating and constant incubation temperatures mimicking those recorded in such nests in the field showed that this nest‐site dichotomy influences the development of the embryos, and the morphology and locomotor performance of the hatchlings. The incubation period increased at fluctuating temperatures and the fact that the rate of embryonic development showed a decelerating pattern with temperature suggests that periods of low temperature had a relatively larger influence on average development than periods of high temperature. Our study demonstrates how a dichotomy in the nesting environments available to female grass snakes in cool climates can affect variation in the duration of the incubation period and offspring phenotypes in ways that may have consequences for fitness. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

Interactive effects of rutin and constant versus alternating temperatures on performance ofManduca sexta caterpillars

The effects of different concentrations of rutin and constant temperature (20 °C) versus alternating temperatures (23∶15 °C) on growth, molting and food utilization efficiencies of third instar tobacco hornworms (Manduca sexta) were determined. Relative consumption rate (RCR) and relative growth rate (RGR) were significantly higher for larvae at the alternating thermal regime compared to those at the constant (representing the average) temperature. With increasing concentrations of rutin, the negative effect of rutin on RCR and RGR increased for the larvae in the alternating thermal regime; however, at the constant temperature, rutin had little effect. The alternating thermal regime promoted synchrony in the timing of spiracle apolysis (the earliest morphological marker of molt). Rutin disrupted that synchrony. I discuss how patterns of host plant resistance may be altered with a decrease, in amplitude of diurnal temperatures (as has been documented recently for temperate regions) through the uncoupling of herbivore performance and allelochemical concentration. I conclude that simultaneous consideration of fluctuating temperatures and allelochemicals is advisable when assessing the effects of temperature and allelochemicals on performance of insect herbivores because interactive effects between temperature and dietary components occur and perhaps are common.     

Effects of the egg incubation environment on turtle carapace development

Developing organisms are often exposed to fluctuating environments that destabilize tissue-scale processes and induce abnormal phenotypes. This might be common in species that lay eggs in the external environment and with little parental care, such as many reptiles. In turtles, morphological development has provided striking examples of abnormal phenotypic patterns, though the influence of the environment remains unclear. To this end, we compared fluctuating asymmetry, as a proxy for developmental instability, in turtle hatchlings incubated in controlled laboratory and unstable natural conditions. Wild and laboratory hatchlings featured similar proportions of supernumerary scales (scutes) on the dorsal shell (carapace). Such abnormal scutes likely elevated shape asymmetry, which was highest in natural nests. Moreover, we tested the hypothesis that hot and dry environments cause abnormal scute formation by subjecting eggs to a range of hydric and thermal laboratory incubation regimes. Shape asymmetry was similar in hatchlings incubated at five constant temperatures (26–30°C). A hot (30°C) and severely Dry substrate yielded smaller hatchlings but scutes were not overtly affected. Our study suggests that changing nest environments contribute to fluctuating asymmetry in egg-laying reptiles, while clarifying the conditions at which turtle shell development remains buffered from the external environment.     

Growth,stress, and acclimation responses to fluctuating temperatures in field and domesticated populations of Manduca sexta

Diurnal fluctuations in temperature are ubiquitous in terrestrial environments, and insects and other ectotherms have evolved to tolerate or acclimate to such fluctuations. Few studies have examined whether ectotherms acclimate to diurnal temperature fluctuations, or how natural and domesticated populations differ in their responses to diurnal fluctuations. We examine how diurnally fluctuating temperatures during development affect growth, acclimation, and stress responses for two populations of Manduca sexta: a field population that typically experiences wide variation in mean and fluctuations in temperature, and a laboratory population that has been domesticated in nearly constant temperatures for more than 300 generations. Laboratory experiments showed that diurnal fluctuations throughout larval development reduced pupal mass for the laboratory but not the field population. The differing effects of diurnal fluctuations were greatest at higher mean temperature (30°C): Here diurnal fluctuations reduced pupal mass and increased pupal development time for the laboratory population, but had little effect for the field population. We also evaluated how mean and fluctuations in temperature during early larval development affected growth rate during the final larval instar as a function of test temperature. At an intermediate (25°C) mean temperature, both the laboratory and field population showed a positive acclimation response to diurnal fluctuations, in which subsequent growth rate was significantly higher at most test temperatures. In contrast at higher mean temperature (30°C), diurnal fluctuations significantly reduced subsequent growth rate at most test temperatures for the laboratory population, but not for the field population. These results suggest that during domestication in constant temperatures, the laboratory population has lost the capacity to tolerate or acclimate to high and fluctuating temperatures. Population differences in acclimation capacity in response to temperature fluctuations have not been previously demonstrated, but they may be important for understanding the evolution of reaction norms and performance curves.     

Physiological adaptation ofMytilus edulis to cyclic temperatures

Summary Mytilus edulis adapted to cyclic temperatures by reducing the amplitude of response of oxygen consumption and filtration rate over a period of approximately two weeks, and thereby increasing their independence of temperature within the range of the fluctuating regime. When acclimated to cyclic temperature regimes within the range from 6 to 20°C, the metabolic and feeding rates, measured at different temperatures in the cycle, were not significantly different from the adapted response to equivalent constant temperatures.Physiological adaptation ofMytilus edulis to different thermal environments was reflected in their metabolic and feeding rate-temperature curves. Animals subjected to marked diel fluctuations in environmental temperature showed an appropriate region of temperature-independence, whereas animals from a population not experiencing large diel temperature fluctuations showed no region of temperature-independence.In a fluctuating thermal environment which extended above the normal environmental maxima, respiratory adaptation occurred at higher temperatures than was possible in a constant thermal environment. The feeding rate was also maintained at higher temperatures in a cyclic regime than was possible under constant thermal conditions. This represented a shortterm extension of the zone of activity in a fluctuating thermal environment. The net result of these physiological responses to high cyclic and constant temperatures has been assessed in terms of scope for growth. Animals acclimated to cyclic temperatures between 21 and 29°C had a higher scope for growth at 29°C and were less severely stressed than those maintained at the constant temperature of 29°C.     

Embryonic development rate and hatchling phenotypes in the Chinese three-keeled pond turtle (Chinemys reevesii): The influence of fluctuating temperature versus constant temperature

Although the effects of constant temperatures on hatchling traits have been extensively studied in reptiles, the effects of fluctuating temperatures remain poorly understood. Eggs of the Chinese three-keeled pond turtle (Chinemys reevesii) were incubated at a constant temperatures (28 °C) and two fluctuating temperatures (28±3 °C and 28±6 °C) to test for the influence of thermal environment on incubation duration, hatchling traits, and post-hatching growth. Incubation duration was shorter at constant temperature than at fluctuating temperatures. The sex ratio of hatchlings varied among temperature treatments, with more females from 28±6 °C than from 28 °C. The size and mass were greater for hatchlings from a constant temperature than from fluctuating ones, but this difference in body size disappeared when the hatchlings were 3 months old. In addition, the swimming ability, survival, and growth of hatchlings from fluctuating temperatures did not differ from those of hatchlings from constant temperature, when they were kept at an artificial environment without food scarcity or predation. Therefore, the thermal environments with various temperature fluctuations used in this study do not significantly affect fitness-related hatchling traits in this species.     

Development, survivorship, and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae) under constant and alternating temperatures

Laboratory studies were conducted to assess the effect of temperature on the survival, development, fecundity, and longevity of Helicoverpa armigera (Hübner) at 11 constant temperatures ranging from 12.5 to 40 degrees C, as well as at five alternating temperature regimes (25-10, 30-15, 32.5-17.5, 35-20, and 35-27.5 degrees C) and under a photoperiod of 16:8 (L:D) h. H. armigera reared at constant temperatures did not develop from egg to adult (emergence) outside the temperature range of 17.5-32.5 degrees C. The alternating conditions expanded this range from 10 to 35 degrees C. The lowest developmental thresholds of the immature stages were estimated by a linear model and ranged from 10.17 (pupal stage) to 11.95 degrees C (egg stage) at constant temperature regimes and from 1.1 to 5.5 degrees C, respectively at alternating temperatures. The values of developmental thresholds estimated using the nonlinear (Lactin-2) model were lower than those estimated by the linear model for constant and alternating temperature regimes except for larval and pupal stages at constant temperatures. Mean adult longevity fluctuated from 34.4 d at 15 degrees C to 7.6 d at 35 degrees C. Females reared under all alternating temperature regimes laid more eggs than females reared at any, except the 25 degrees C, constant temperature treatment. The intrinsic rate of increase was highest at 27.5 degrees C, at both the constant and the corresponding alternating temperature regimes (0.147 and 0.139, respectively). Extreme temperatures had a negative effect on life table parameters.     

变温对粘虫生殖及主要能源物质代谢的影响

【目的】明确变温与粘虫Mythimna separata(Walker)生长发育和生殖的关系及变温条件下粘虫主要能源物质代谢的变化规律。【方法】将粘虫卵置于光周期均为14L∶10D,温度分别为25℃和30℃日恒温和白天30℃、夜晚20℃日变温的条件下饲养,观察记录25℃和30/20℃下的成虫产卵及卵巢管发育情况,再取30℃和30/20℃下饲养获得的3龄幼虫、6龄幼虫、蛹和1日龄成虫,测定其糖原、海藻糖和甘油三酯3种能源物质的含量及海藻糖酶、3-磷酸甘油醛脱氢酶、3-磷酸甘油脱氢酶及3-羟酰辅酶A脱氢酶等4种主要能源物质代谢酶的活性。【结果】25℃与30/20℃饲养条件下相比,1日龄雌成虫卵巢管发育明显滞后,但单雌产卵量显著较多;蛹期糖原、海藻糖和甘油三酯的含量均高于3龄和6龄幼虫,成虫期各能源物质含量均较低。30/20℃日变温下粘虫体内供试3种能源物质的含量显著高于30℃日恒温(6龄幼虫和蛹期甘油三酯含量在两温度下无显著差异);温度变化对供试4种酶活性的影响差异显著。【结论】温度变化对粘虫的生长发育和繁殖具有显著的影响。在粘虫生长发育过程中以糖代谢为主;变温会加速糖代谢,减缓部分发育阶段的脂代谢,更有利能源物质的积累。     

Effects of Fluctuating Daily Temperatures at Critical Thermal Extremes on Aedes aegypti Life-History Traits

Background

The effect of temperature on insect biology is well understood under constant temperature conditions, but less so under more natural, fluctuating conditions. A fluctuating temperature profile around a mean of 26°C can alter Aedes aegypti vector competence for dengue viruses as well as numerous life-history traits, however, the effect of fluctuations on mosquitoes at critical thermal limits is unknown.

Methodology/Principal Findings

We investigated the effects of large and small daily temperature fluctuations at low (16°C) and high (35–37°C) mean temperatures, after we identified these temperatures as being thresholds for immature development and/or adult reproduction under constant temperature conditions. We found that temperature effects on larval development time, larval survival and adult reproduction depend on the combination of mean temperature and magnitude of fluctuations. Importantly, observed degree-day estimates for mosquito development under fluctuating temperature profiles depart significantly (around 10–20%) from that predicted by constant temperatures of the same mean. At low mean temperatures, fluctuations reduce the thermal energy required to reach pupation relative to constant temperature, whereas at high mean temperatures additional thermal energy is required to complete development. A stage-structured model based on these empirical data predicts that fluctuations can significantly affect the intrinsic growth rate of mosquito populations.

Conclusions/Significance

Our results indicate that by using constant temperatures, one could under- or over-estimate values for numerous life-history traits compared to more natural field conditions dependent upon the mean temperature. This complexity may in turn reduce the accuracy of population dynamics modeling and downstream applications for mosquito surveillance and disease prevention.     

Phenotypic responses of hatchlings to constant versus fluctuating incubation temperatures in the multi-banded krait, Bungarus multicintus (Elapidae)

Most studies on egg incubation in reptiles have relied on constant temperature incubation in the laboratory rather than on simulations of thermal regimes in natural nests. The thermal effects on embryos in constant-temperature studies often do not realistically reflect what occurs in nature. Recent studies have increasingly recognized the importance of simulating natural nest temperatures rather than applying constant-temperature regimes. We incubated Bungarus multicintus eggs under three constant and one fluctuating-temperature regimes to evaluate the effects of constant versus fluctuating incubation temperatures on hatching success and hatchling phenotypes. Hatching success did not differ among the four treatments, and incubation temperature did not affect the sexual phenotype of hatchlings. Incubation length decreased as incubation temperature increased, but eggs incubated at fluctuating temperatures did not differ from eggs incubated at constant temperatures with approximately the same mean in incubation length. Of the hatchling phenotypes examined, residual yolk, fat bodies and locomotor performance were more likely affected by incubation temperature. The maximal locomotor speed was fastest in the fluctuating-temperature and 30 degrees C treatments and slowest in the 24 degrees C treatment, with the 27 degrees C treatment in between. The maximal locomotor length was longest in the fluctuating-temperature treatment and shortest in the 24 degrees C and 27 degrees C treatments, with the 30 degrees C treatment in between. Our results show that fluctuating incubation temperatures do not influence hatching success and hatchling size and morphology any differently than constant temperatures with approximately the same mean, but have a positive effect on locomotor performance of hatchlings.     

Development of Rhodnius prolixus (Hemiptera: Reduviidae) under constant and cyclic conditions of temperature and humidity.

Development of Rhodnius prolixus after eclosion until the adult stage was studied at constant temperatures (T), 15, 20, 25, 28, 35 C, and relative humidities (RH), 75, 86 and 97%, and fluctuating (16/8 hr) temperatures, T I/II, 15/28 C, 20/25 C, 25/28 C and 25/35 C, and relative humidities, RH I/II, 86/75% and 97/75%. Eclosion or molting were not observed at 15 C and 86 or 97% RH, respectively. At 35 C and 75% RH only few insects molted. By alternating T I/II, 15/28 C and 25/35 C, insects developed at high frequency. Cumulating the average lengths of the interphases within independent groups for each instar, R. prolixus reached the adult stage most rapidly (86.7 days) and at highest frequency per instar (mean: 91.8%) at 28 C and 75% RH. Under fluctuating T I/II, development was completed within 100 days or less at 25/28 C and 25/35 C with high rates of hatch and molting. Development was slowest at fluctuating TI/II, 15/28 C and 20/25 C (>185 days), and at constant 20 C (>300 days). Mortality was higher at constant 97% RH or fluctuating RH I, 97%, than at constant or fluctuating 86% RH. Refeeding was minimal at optimal conditions of T and RH for development. The most refeeding was observed at a constant 35 C.     

Effects of constant and changing temperature conditions on diapause induction in Helicoverpa armigera (Lepidoptera: Noctuidae)

The effects of photoperiod and temperature on the induction and termination of facultative pupal diapause in Helicoverpa armigera (Lepidoptera: Noctuidae) were investigated under laboratory conditions. Exposing H. armigera larvae to both constant and fluctuating temperature regimes with a mean of 25°C and 20°C resulted in a type-III photoperiodic response curve of a short-long day insect. The long-day critical daylengths for diapause induction were ten hours and 12 hours at the constant temperatures of 25°C and 20°C, respectively. Higher incidences of diapause and higher values both for the longer and the shorter critical photoperiods for diapause induction were observed at fluctuating regimes compared with the corresponding constant ones. At alternating temperatures, the incidence of diapause ranged from 4.2% to 33.3% and was determined by the temperature amplitude of the thermoperiod and by the interaction of cryophase or thermophase with the photoperiod. Helicoverpa armigera larvae seem to respond to photoperiodic stimuli at temperatures >15°C and <30°C; all insects entered diapause at a constant temperature of 15°C, whereas none did so at a constant temperature of 30°C under all the photoperiodic regimes examined. Although chilling was not a prerequisite for diapause termination, exposure of diapausing pupae to chilling conditions significantly accelerated diapause development and the time of adult emergence. Therefore, temperature may be the primary factor controlling the termination of diapause in H. armigera.     

Population development of Frankliniella occidentalis and Thrips hawaiiensis in constant and fluctuating temperatures

Temperature fluctuations may influence the behaviour of insects. Frankliniella occidentalis and Thrips hawaiiensis are sympatric pests on flower and vegetable host plants in China. This study evaluated the influence of constant (23.0°C) and fluctuating temperatures (average of 23.0°C) on the population development of these two species. The results showed that both of these pests showed faster development and higher fecundity at a constant temperature than at fluctuating temperatures when fed on Rosa rugosa flowers, and F. occidentalis showed faster development and higher fecundity than T. hawaiiensis under both conditions. Under the constant and fluctuating temperatures, the development times from egg to adult were 9.57 and 10.62 day for F. occidentalis and 10.71 and 11.82 day for T. hawaiiensis, respectively. The total numbers of first instar nymph produced were 103.08 and 86.32 by F. occidentalis, 86.96 and 73.32 by T. hawaiiensis, under the constant and fluctuating temperatures, respectively, and a higher intrinsic rate of natural increase (r_m) (0.173 and 0.160) and R₀ (46.31 and 36.86) were obtained in F. occidentalis compared with T. hawaiiensis (r_m for 0.154 and 0.141 and R₀ for 34.46 and 27.81, respectively). Our results indicate that the constant temperature had a positive effect on the population development of both F. occidentalis and T. hawaiiensis. Furthermore, F. occidentalis showed a stronger adaptability over T. hawaiiensis at both constant and fluctuating temperatures, according to its faster development and higher fecundity. These results may contribute to the better understanding of the biology of different thrip species, especially the interspecific competition between invasive and native thrips under the changing environment. These findings also provide basic data for the thrip pests control by using fluctuating temperatures.     

恒定和波动温度下丽斑麻蜥孵出幼体的表型变异

作者以丽斑麻蜥(Eremias argus)为模型动物研究恒定和波动孵化温度对孵化成功率和孵出幼体表型的影响。卵在四个恒定[24 ,27 ,30 and 33 (±0·3)℃]、一个波动温度下孵化。不同温度处理下的孵化成功率相同,但孵出幼体表型不同。孵化期随孵化温度升高呈指数式缩短;在相同平均温度下,波动温度孵化卵的孵化期比恒温孵化卵长。在所有被检表型特征中,幼体的干重、剩余卵黄干重和运动表现更易受孵化温度影响。总体而言,低温(24℃、27℃)孵出幼体运动表现最佳,高温(33℃)孵出幼体最差、温和温度(30℃和波动温度)孵出幼体居中。本文研究数据显示: (1)丽斑麻蜥卵每日短期暴露于潜在致死的极端温度下对孵化成功率和孵出幼体形态特征无明显的不利效应; (2)温度波动对孵出幼体运动表现无促进作用,对孵化期的影响则不同于平均值相同的恒定温度。     

Influence of different temperatures on the tachinid parastite,Sturmiopsis inferens [Dip.]

The influence of constant temperatures of 27, 29, 31 and 33°C and alternating temperature of 31/33°C (18/6 h) onSturmiopsis inferens Townsend was studied during 12 successive generations. The larval and pupal periods for male parasites were 13.5±0.5 and 11.0±0.3 days respectively and for female 12.8±0.5 and 11.1±0.3 days respectively in the 1st generatioin at 27°C. It decreased progressively with increase in temperature. Survival of females, fertility and fecundity were adversely affected at higher temperatures. A temperature range of 27–29°C appeared to be optimum for mass rearing of the parasite in the laboratory. The higher premature mortality observed at a constant 33°C was not observed at temperatures fluctuating between 31/33°C. Presumably under field conditions, where temperature is constantly fluctuating, the flies will be able to withstand a comparatively higher temperature.     

Effects of variable and constant temperatures on the embryonic development and survival of a new grape pest, Xylotrechus arvicola (Coleoptera: Cerambycidae)

Xylotrechus arvicola Olivier (Coleoptera: Cerambycidae) has become a new expanding pest in grape (Vitis spp.) crops. To better improve control tactics, the consequences of 11 constant (12, 15, 18, 21, 24, 27, 30, 32, 34, 35 and 36°C) and nine variable temperatures (with equal mean temperatures at each of the nine constant rates ranging from 15 to 35°C) on survival and embryonic development were studied. The eggs were able to complete development at constant temperatures between 15 and 35°C, with mortality rates at the extremes of the range of two and 81.5%, respectively. Using variable temperatures a mortality rate of 38.9% at a mean temperature of 15°C and 99% at 35°C was observed. The range of time for embryonic development was 29.5 d at 15°C to 6 d at 32°C at constant temperatures, and from 29.6 d at 15°C to 7.2 d at 32°C at variable temperatures. The goodness-of-fit of different development models was evaluated for the relationship between the development rate and temperature. The models that gave the best fit were the Logan type III for constant temperatures and the Brière for variable temperatures. Optimum temperatures were estimated to be from 31.7 to 32.9°C. The models that best described embryo development under natural field conditions were the Logan type III model for constant temperatures (98.7% adjustment) and the Lactin model for variable temperatures (99.2% adjustment). Nonlinear models predicted faster development at constant temperatures and slower development at variable ones when compared with real field development, whereas the linear model always predicted faster development than what actually took place.