Effect of photoperiod on development and growth in a pentatomid bug, Dolycoris baccarum

The effect of photoperiod on nymphal development, growth and adult size was examined in a pentatomid bug, Dolycoris baccarum , collected in Osaka (a warm temperate region) and Hokkaido (a subfrigid region), Japan. When insects were reared from eggs at 25°C, the developmental period was long and adult size was large under photoperiods close to the critical photoperiod for the induction of adult diapause. Adults of the Hokkaido population were larger than those of the Osaka population. There was no significant correlation between developmental period and adult size. Insects also showed variation in their growth rate: growth rate was low under photoperiods a little longer than the critical photoperiod for the induction of diapause. The ecological significance of variation in development and growth is discussed.     

Effect of gestational and postnatal environmental temperature on metabolic rate in the altricial rodent, Phyllotis darwini

1. In the altricial rodent, Phyllotis darwini, we found higher body temperatures and faster developmental rates of the thermoregulatory capacity in neonates born from cold- than warm-acclimated mothers.

2. This difference could be explained by maternal effects on the litter, such as high levels of catecholamines and thyroxin levels, high concentration of the uncoupled protein and larger quantity of brown adipose tissue as a consequence of cold acclimation.

3. The exposition of mothers and the maintenance of cold condition during the early development might be responsible of the high metabolism and better thermoregulatory capacity of newborns.

Effects of diet, photoperiod and temperature on the postdiapause reproduction in the cabbage bug,Eurydema rugosa

InEurydema rugosa Motschulsky (Heteroptera: Pentatomidae), the type of food supplied (i.e. seeds or leaves of the brown mustard,Brassica juncea Hemsel) and photoperiod, which control the induction of adult diapause, do not play a role in the initiation of reproduction after overwintering. A temperature above 13.2°C was required to start reproduction. After its initiation, however, short-day conditions on seeds induced diapause again in some adults. Although a diet of seeds under long-day conditions, in common with short-day conditions, induced diapause in young adults (Numata & Yamamoto, 1990), it did not reinduce diapause in adults after overwintering. Thus,E. rugosa that had overwintered became sensitive to diapause-inducing photoperiod again but not to dietary factors.     

Within- and between-generation effects of temperature on life-history traits in a butterfly

Non-genetic parental effects may largely affect offspring phenotype, and such plasticity is potentially adaptive. Despite its potential importance, little is known about cross-generational effects of temperature, at least partly because parental effects were frequently considered a troublesome nuisance, rather than a target of experimental studies. We here investigate effects of parental, developmental and acclimation temperature on life-history traits in the butterfly Bicyclus anynana. Higher developmental temperatures reduced development times and egg size, increased egg number, but did not affect pupal mass. Between-generation temperature effects on larval time, pupal time, larval growth rate and egg size were qualitatively very similar to effects of developmental temperature, and additionally affected pupal mass but not egg number. Parental effects are important mediators of phenotypic plasticity in B. anynana, and partly yielded antagonistic effects on different components of fitness, which may constrain the evolution of cross-generational adaptive plasticity.     

Effect of day length on oxidative capacities of mitochondria from red muscle of rainbow trout (Oncorhynchus mykiss)

In nature, seasons may be more reliably announced by changes in photoperiod than in temperature. To evaluate the role of day length in setting oxidative capacities of trout muscle mitochondria, we acclimated trout to summer (15 °C, 16L:8D), winter (5 °C, 8L:16D) and mixed conditions (15 °C, 8L:16D). Maximal oxidative capacities of isolated mitochondria at 5 and 15 °C were higher in mixed than summer conditions and higher again in winter conditions. At 5 °C, state 4 rates changed little with acclimation state whereas at 15 °C state 4 rates were lower in summer than in mixed or winter conditions. Using concentrations of the adenylate nucleotide translocase as the denominator for these rates gave much the same conclusions. By using inhibitors to block flux at specific points in the electron transport chain, we found that flux through Complexes II–IV was lowest in summer acclimated trout, increased upon acclimation to mixed and to winter conditions. Flux through complex IV was similar in trout acclimated to summer and mixed conditions, but increased significantly with acclimation to winter conditions. Flux through complex IV was 1.5 fold higher than state 3 rates for summer-acclimated trout but was similar to state 3 rates in trout acclimated to mixed or winter conditions. Our results indicate that a reduction in day length initiates increases in mitochondrial oxidative capacity typically associated with cold acclimation and that acclimation to both cold temperatures and short day lengths enhanced these changes. The overall similarity of the responses of state 3, of flux through complexes II–IV and of flux through complex IV suggests that a generalised mechanism such as changes in the phospholipid composition of the inner mitochondrial membrane may coordinate these changes.     

Multiple effects of temperature,photoperiod and food quality on the performance of a pine sawfly

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Seasonal effects on metabolism and thermoregulation abilities of the Red-winged Starling (Onychognathus morio)

Basal metabolic rate (BMR) of birds is beginning to be viewed as a highly flexible physiological trait influenced by environmental fluctuations, and in particular changes in ambient temperatures (T_a). Southern Africa is characterized by an unpredictable environment with daily and seasonal variation. This study sought to evaluate the effects of seasonal changes in T_a on mass-specific resting metabolic rate (RMR), BMR and body temperature (T_b) of Red-winged Starlings (Onychognathus morio). They have a broad distribution, from Ethiopia to the Cape in South Africa and are medium-sized frugivorous birds. Metabolic rate (VO₂) and T_b were measured in wild caught Red-winged Starlings after a period of summer and winter acclimatization in outdoor aviaries. RMR and BMR were significantly higher in winter than summer. Body mass of Starlings was significantly higher in winter compared with summer. The increased RMR and BMR in winter indicate improved ability to cope with cold and maintenance of a high T_b. These results show that the metabolism of Red-winged Starlings are not constant, but exhibit a pronounced seasonal phenotypic flexibility with maintenance of a high T_b.     

低温对小菜蛾实验种群的影响

研究了低温(<8℃)对小菜蛾的发育、存活和繁殖的影响.结果表明,卵和蛹在4℃和6℃下死亡率随处理时间的延长而增加,在分别处理55d和70d后,卵和蛹全部死亡;经4℃和6℃处理的蛹,在16℃下羽化成虫的平均产卵量随处理时间的延长而减少,处理45d时,产卵量均为0.小菜蛾幼期各虫态在0℃以下,死亡率随低温强度加大和处理时间的延长而增高.就耐寒力而言,3龄幼虫和蛹最强,其次是2龄和4龄幼虫,卵和1龄幼虫的耐寒力最弱.不同低温和时间处理小菜蛾幼期虫态对其后继虫态的发育历期有较大影响,总体说来,经过处理的小菜蛾幼期虫态,其后继虫态的发育历期普遍延长,一般处理某一虫态对其相邻虫态发育历期的影响最大.小菜蛾蛹经低温处理后其羽化成虫的产卵量随着蛹期所经历低温强度的增强和时间延长而减少.     

Seasonal variation in metabolic rate of a medium-sized frugivore, the Knysna Turaco (Tauraco corythaix)

Many seasonal thermoregulation studies have been conducted on Holarctic birds that live in predictable, highly seasonal climates with severe winters. However, relatively few studies have been conducted on their southern hemisphere Afrotropical counterparts that encounter less predictable climates with milder winters. These latter birds are expected to conserve energy in winter by downregulating their metabolic rates. Therefore in this study, metabolic rate was measured during summer and winter in Knysna Turaco, Tauraco corythaix (Musophagiformes, Musophagidae) (c. 310 g), a non-passerine, in order to test whether there is energy conservation in winter. No overall significant differences in resting metabolic rates over a range of ambient temperatures were observed between winter and summer. However, whole-organism basal metabolic rates were 18.5% higher (p=0.005) in winter than in summer (210.83±15.97 vs. 186.70±10.52 O₂ h⁻¹). Knysna Turacos had broad thermoneutral zones ranging from 20 to 28 °C in winter and 10 to 30 °C in summer. These results suggest that Knysna Turacos show seasonal thermoregulatory responses that represent cold defense rather than energy conservation, which is contrary to what was expected.     

The underestimated role of temperature–oxygen relationship in large‐scale studies on size‐to‐temperature response

The observation that ectotherm size decreases with increasing temperature (temperature‐size rule; TSR) has been widely supported. This phenomenon intrigues researchers because neither its adaptive role nor the conditions under which it is realized are well defined. In light of recent theoretical and empirical studies, oxygen availability is an important candidate for understanding the adaptive role behind TSR. However, this hypothesis is still undervalued in TSR studies at the geographical level. We reanalyzed previously published data about the TSR pattern in diatoms sampled from Icelandic geothermal streams, which concluded that diatoms were an exception to the TSR. Our goal was to incorporate oxygen as a factor in the analysis and to examine whether this approach would change the results. Specifically, we expected that the strength of size response to cold temperatures would be different than the strength of response to hot temperatures, where the oxygen limitation is strongest. By conducting a regression analysis for size response at the community level, we found that diatoms from cold, well‐oxygenated streams showed no size‐to‐temperature response, those from intermediate temperature and oxygen conditions showed reverse TSR, and diatoms from warm, poorly oxygenated streams showed significant TSR. We also distinguished the roles of oxygen and nutrition in TSR. Oxygen is a driving factor, while nutrition is an important factor that should be controlled for. Our results show that if the geographical or global patterns of TSR are to be understood, oxygen should be included in the studies. This argument is important especially for predicting the size response of ectotherms facing climate warming.     

Testing the beneficial acclimation hypothesis: temperature effects on mating success in a butterfly

Traditionally, it has been assumed that all acclimation changesto the phenotype enhance the performance of an individual organismin the environment in which those changes were induced (beneficialacclimation hypothesis [BAH]), a theory that has been repeatedlychallenged in recent years. We here use a full-factorial designwith 2 developmental and 2 acclimation temperatures to testtheir effects on reproductive performance in the tropical butterfly,Bicyclus anynana. Competition experiments among virgin malesfrom different thermal groups revealed that, at 20 °C, bothgroups acclimated to 20 °C achieved more than twice as manymatings as those acclimated to 27 °C, whereas at 27 °C,only one group (acclimated to 27 °C) outperformed all others.Chill-coma recovery times were also longer for butterflies thatdeveloped at higher temperatures, indicating that butterfliesresponded physiologically to the temperatures at which theywere reared. Our results support the BAH at least in part, anddo not support any alternative hypotheses.     

Effects of habitat drying on size at and time to metamorphosis in the tree hole mosquito Aedes triseriatus

Models of complex life cycles predict that greater mortality of immature stages should induce earlier metamorphosis at smaller sizes. We tested for effects of one source of mortality, habitat drying, on size at and time to metamorphosis of the tree hole mosquito Aedes triseriatus. In a laboratory experiment, we manipulated two variables associated with drying, volume of water and solute concentration, and recorded mean mass at and median days to eclosion for males and females in replicate cohorts. We also tested for treatment effects on the correlation of mass at and time to eclosion. For females, decreasing volume consistently induced metamorphosis at smaller sizes than did constant volume. Decreasing volume also led to earlier metamorphosis of females than did constant volume, but only in one of two experimental runs. For both sexes, increasing concentration led to greater size at metamorphosis and, for males, earlier metamorphosis than did constant volume, but again only in one of two experimental runs. Correlations of size at and time to metamorphosis tended to be positive for females and negative for males, and this difference was significant. For both sexes, decreasing volume led to larger (more positive) correlations than did constant volume, but only in one of two experimental runs. The effects of decreasing volume on females are consistent with the predictions of models of complex life cycles, and suggest that A. triseriatus can perceive volume changes and modify metamorphosis to escape a deteriorating habitat. The effects of increasing concentration are opposite to those predicted, and are consistent with enhanced growth rates, possibly due to enhanced microbial growth, as solutes become concentrated due to drying. The responses of these mosquitoes to habitat drying are complex, and we suggest that habitat drying increases both mortality and growth rates, yielding no simple predictions of how habitat drying will affect these mosquitoes in natural tree holes.     

Direct effects of incubation temperature on morphology,thermoregulatory behaviour and locomotor performance in jacky dragons (Amphibolurus muricatus)

Incubation temperature is one of the most studied factors driving phenotypic plasticity in oviparous reptiles. We examined how incubation temperature influenced hatchling morphology, thermal preference and temperature-dependent running speed in the small Australian agamid lizard Amphibolurus muricatus. Hatchlings incubated at 32 °C grew more slowly than those incubated at 25 and 28 °C during their first month after hatching, and tended to be smaller at one month. These differences were no longer significant by three months of age due to selective mortality of the smallest hatchlings. The cooler incubation treatments (25 °C and 28 °C) produced lizards that had deeper and wider heads. Hatchlings from 28 °C had cooler and more stable temperature preferences, and also had lower body temperatures during a 2-h thermoregulatory behaviour trial. Locomotor performance was enhanced at higher body temperatures, but incubation temperature had no measurable effect either independently or in interaction with body temperature. Our study demonstrates that incubation temperature has direct effects on morphology and thermoregulatory behaviour that appears to be independent of any size-dependent effects. We postulate a mechanistic link between these two effects.     

Predation induced changes in behavior and growth rate in three populations of the intertidal snail, Littorina sitkana (Philippi)

We investigated the sublethal effects of a predatory crab, Cancer productus (Randall), on the behavior and growth of its snail prey, Littorina sitkana, by setting up controlled rearing and prey-size selection experiments. L. sitkana were collected from three sites on San Juan Island, WA, USA. These sites varied in snail size, abundance, and vertical distribution, and in the abundance of the crab predator C. productus. Snails from all three populations were raised for 34 days under the following treatments: no-crab control, a non-feeding C. productus encased in mesh box, and an encased C. productus feeding on L. sitkana. The non-feeding crab treatment did not affect snail foraging behavior or growth rate in comparison with the no-crab control. In contrast, the presence of a feeding crab elicited escape behavior in the snails, halted grazing, and consequently reduced growth rates. A population difference in escape behavior was observed: upward migration in snails from rocky shores and hiding in crevices in snails from a mud flat. It thus appears that chemicals leaching from crushed conspecific snails, rather than the presence of the crab predator, act as the “alarm substance” to which L. sitkana react. The magnitude of the growth depression in the presence of feeding crabs was 85%, with no difference among the three populations. Once the feeding crab stimulus was removed, snails in all populations resumed normal growth, suggesting that this response to feeding predators is reversible with changing environmental conditions. Laboratory experiments were set up to determine if all size classes of L. sitkana are equally susceptible to C. productus predation. C. productus consistently selected the largest of three size classes of L. sitkana. These results suggest that slow growth rate and small size in L. sitkana may actually be an adaptation for coexisting with high C. productus abundance, rather than simply a cost of escape behavior.     

Interactions of environmental temperature with photoperiod in determining age at maturity in a semelparous polychaete Nereis (neanthes) virens sars

1. 1. Larger members of the Polychacta exhibit two contrasting life cycles: semelparous in the Nereidae, iteroparous in most others.

2. 2. In semelparous forms environmental interaction determines age at reproduction and fecundity in the single spawning event whereas in iteroparous forms such interaction influences the variable age specific reproductive effort.

3. 3. Development of aquaculture has created conditions where organisms are grown under conditions of optimum temperature for growth and unlimited food.

4. 4. We present data on the life history responses (reaction norms) of the semelparous Nereis virens in which age at death in natural populations varies between 3 to 8+ years.

5. 5. In Nereis virens minimum life span (= generation time) in culture is one year but the lifespan remains modular 12 months without manipulation of photoperiod.

6. 6. Environmental temperature plays two roles: i) in conjunction with energy availability to determine “age at first/only reproduction” and secondly as an element (with photoperiod) in the control of gametogenic processes imposing seasonality on the life cycle.

7. 7. The observations suggest that long generation time in natural populations of N. virens is associated with reduced growth rate and that low growth rate is associated with reproduction at a larger size.

     

Plasticity in the timing of physiological development: Physiological heterokairy — What is it, how frequent is it, and does it matter?

The study of developmental sequences of physiological traits could be an important way of placing comparative developmental physiology (CDP) within the research agenda being forged by work on developmental plasticity. Here we focus on the concept of heterokairy defined by Spicer & Burggren in 2003 as changes in the timing of physiological development in an individual. The role of this concept in the future of the CDP is discussed. First we provide an historical perspective of the ideas that have led to the investigation of sequences in CDP. This is followed by a re-examination and clarification of the definition of physiological heterokairy before empirical case studies that (explicitly or implicitly) demonstrate physiological heterokairy are reviewed. We suggest that physiological heterokairy can be demonstrated through a wide range of invertebrate and vertebrate examples. However, care must be taken when inferring that heterokairy as a pattern is always the result of heterokairic processes as there is evidence that physiological heterokairy could result from the altered timing of both homologous or analogous physiological mechanisms. We conclude by discussing the potential link between heterokairy and heterochrony and suggest that the investigation of this link should be a major goal for workers in both CDP and developmental plasticity.     

Influence of temperature and photoperiod on embryonic development in the dragonfly Sympetrum striolatum (Odonata: Libellulidae)

Temperature and photoperiod play major roles in insect ecology. Many insect species have fixed degree‐days for embryogenesis, with minimum and maximum temperature thresholds for egg and larval development and hatching. Often, photoperiodic changes trigger the transfer into the next life‐cycle stadium. However, it is not known whether this distinct pattern also exist in a species with a high level of phenotypic plasticity in life‐history traits. In the present study, eggs of the dragonfly Sympetrum striolatum Charpentier (Odonata: Libellulidae) are reared under different constant and fluctuating temperatures and photoperiodic conditions in several laboratory and field experiments. In general, and as expected, higher temperatures cause faster egg development. However, no general temperature or light‐days for eyespot development and hatching are found. The minimum temperature thresholds are distinguished for survival (2 °C), embryogenesis (6 °C) and larval hatching (above 6 °C). Low winter temperatures synchronize hatching. Above 36 °C, no eyespots are visible and no larvae hatch. In laboratory experiments, light is neither necessary for eyespot development, nor for hatching. By contrast to the laboratory experiments, the field experiment show that naturally changing temperature and photoperiod play a significant role in the seasonal regulation of embryonic development. The post‐eyespot development is more variable and influenced by temperature and photoperiod than the pre‐eyespot development. This developmental plasticity at the end of the embryogenesis might be a general pattern in the Libellulidae, helping them to cope with variation in environmental conditions.     

Effect of temperature on growth of juvenile Oreochromis mossambicus and Sarotherodon melanotheron

Synopsis Survival and competitive ability of juvenile fish is often dependent on their growth rate. Temperature is the physical component of their environment which most affects growth rate. To determine the effect of temperature on the growth rate of two exotic warm water species we measured growth of Oreochromis mossambicus and Sarotherodon melanotheron at 25, 30 and 35°C. There was a significant interaction of species and temperature on growth. The growth rate of O. mossambicus was faster than that of S. melanotheron at 25 and 30°C but slower at 35°C. Weight gain of S. melanotheron was significantly greater at 30°C than at 25°C. Weight gain of O. mossambicus at 25 and 30°C was significantly greater than at 35°C. Temperature had no effect on the weight-length relationship of either species.Scientific Series No. 1546-AEL from UM-CEES, Appalachian Environmental Laboratory     

Plasticity of life-cycle, physiological thermal traits and Hsp70 gene expression in an insect along the ontogeny: Effect of temperature variability

It is considered that extreme environmental temperature, rather than mean temperatures exert a selective pressure in ectotherms. Consequently, it is important to understand how the predicted increase in temperature variance with a higher frequency of extreme events in climate change is likely to impact on organisms. Thermal tolerance traits (i.e. chill-coma, recovery time, Hsp70 expression) are directly linked with performance in ectotherms and have consequences in life-history traits. We examined the effects of temperature variability on thermal tolerance and life-history traits through ontogeny of an insect with a complex life-cycle: the yellow mealworm beetle Tenebrio molitor. We established two common gardens with 100 recently ovoposited eggs each. Larvae were reared from hatching to adult on either a variable (mean=18 °C and a variance of 6.8 °C) or constant (18±1 °C) thermal environment. Development rate and growth rate were similar between thermal environments. Results indicate that larvae reared in a variable environment are more cold-tolerant than larvae of a constant environment. Interestingly, these results are reversed in the adult stage, outlining an inter-stage physiological cost. Gene expression pattern of an Hsp70 gene was well correlated with larval thermotolerance to cold in the variable environment but higher gene expression in adults is not correlated with individual's thermotolerance. We conclude that chill-coma, recovery time and Hsp70 gene expression are plastic in response to a thermal environment but also change significantly their responses depending on the ontogenetic stage, implying that the response of adult individuals is linked to early stages of the life-cycle.     

Effect of temperature,photoperiod, and feeding on the rate of tail regeneration in a semiaquatic plethodontid salamander

Salamander tail autotomy improves survival, but loss of the tail can subsequently be costly. For example, burst swimming speed is significantly slower after autotomy in desmognathan salamanders, which may increase predation risk in aquatic habitats. However, any long-term cost of tail loss is contingent on the rate of tail regeneration. To examine variation among seasons and environments in the cost of tail autotomy, we tested the effect of temperature, photoperiod, and feeding on tail-length re-growth in the semiaquatic plethodontid salamander Desmognathus conanti. Eight experimental groups (n=15 each, equivalent in body size) were tested. After acclimation for four weeks at one of two temperatures (either 10 °C or 20 °C) and one of two photoperiods (either L:D 9.5:14.5 h or 14.5:9.5 h), 60% of the tail length was autotomized for each individual. After autotomy, each experimental group was maintained under unique conditions of temperature (either 10 °C or 20 °C), photoperiod (either L:D 9.5:14.5 h or 14.5:9.5 h), and feeding (either fasting or weekly feeding). The length of the regenerated tail portion for each individual was measured each week until the group with the fastest re-growth had regenerated 50% of the lost tail length. Low temperature had a large, negative effect, fasting had a small, negative effect, but photoperiod had no significant effect on tail re-growth. The large thermal effect resulted from a combination of delayed initiation of tail-length re-growth and reduced regeneration rate thereafter at low temperature. We conclude that the cost of salamander tail autotomy differs among seasons and environments based on variation in temperature and food availability.