•Fluctuating thermal and hydration regimes (FTR and FHR) were investigated.•Water and lipid content, metabolic rate, total protein and HSP70 were measured.•FTR are protective and increases HSP70, but ...show long-term fitness consequences.•FHR decreases cuticular water loss but survival is similar to constant controls.•Regulation of metabolic rate is likely responsible for FTR and FHR protection.
Fluctuating thermal regimes (FTR), consisting of cycles between stressful low and benign temperatures, are known to improve survival and fecundity in a variety of insects. By contrast, fluctuating hydration regimes (FHR) consisting of cycles between dehydrating and benign conditions have been less comprehensively researched. Hypothetically, either repeated stress accumulates damage and reduces survival, or the recovery periods may act as a protective mechanism by allowing low temperature- or dehydration-induced damage to be repaired. Using false codling moth (Thaumatotibia leucotreta) larvae, we investigated whether FTR and FHR resulted in protection, or accumulated damage, at the cellular and whole-organism levels. Time- and age-matched controls were used to verify that the effects were due to the fluctuating stressors and not age- or time-dependent responses. Results showed that larval body water-(BWC) and lipid content (BLC) remained unchanged in response to FTR. Importantly though, FTR are protective when compared to constant low temperature exposures, potentially due to an increase in heat shock protein 70 (HSP70). However, larvae may suffer long-term fitness consequences compared to constant benign exposures. Results for FHR appear equivocal when compared to constant controls, due to high survival rates for all experiments, although the physiological responses to FHR included a decrease in larval BWC and BLC, a decrease in cuticular water loss rates, and a depletion of HSP70 during the final dehydration cycle. In conclusion, it appears that fluctuating stressors are protective in T. leucotreta when compared to constant stress conditions, likely through regulation of whole-animal metabolic rate and HSP70, although other mechanisms (e.g. ion homeostasis) are also implicated.
•Acclimation capacity is critically important for thermal tolerance of insects.•Thermal acclimation is unlikely to rescue species currently challenged by global warming.•Plasticity (acclimation ...capacity) in thermal limits is weakly correlated with latitude.•Plasticity in thermal limits evolves slowly.•Simple laboratory measures do often not capture the complexity of plasticity.
Phenotypic plasticity of temperature tolerance (thermal acclimation) is often highlighted as an important component of the acute and evolutionary adaptation to temperatures in insects. For this reason, it is often suggested that thermal acclimation ability could be important for buffering the consequences of climate change. Based on data from Drosophila we discuss if and how phenotypic plasticity is likely to mitigate the effects of climate change. We conclude that plasticity of upper thermal limits is small in magnitude, evolves slowly and that acclimation ability is weakly correlated with latitude and environmental heterogeneity. Accordingly plasticity in upper thermal limits is unlikely to effectively buffer effects of global warming for species already close to their upper thermal boundaries.
Organisms are exposed to temperatures that vary, for example on diurnal and seasonal time scales. Thus, the ability to behaviorally and/or physiologically respond to variation in temperatures is a ...fundamental requirement for long-term persistence. Studies on thermal biology in ectotherms are typically performed under constant laboratory conditions, which differ markedly from the variation in temperature across time and space in nature. Here, we investigate evolutionary adaptation and environmentally induced plastic responses of
to no fluctuations (constant), predictable fluctuations or unpredictable fluctuations in temperature. We whole-genome sequenced populations exposed to 20 generations of experimental evolution under the three thermal regimes and examined the proteome after short-term exposure to the same three regimes. We find that unpredictable fluctuations cause the strongest response at both genome and proteome levels. The loci showing evolutionary responses were generally unique to each thermal regime, but a minor overlap suggests either common laboratory adaptation or that some loci were involved in the adaptation to multiple thermal regimes. The evolutionary response, i.e., loci under selection, did not coincide with induced responses of the proteome. Thus, genes under selection in fluctuating thermal environments are distinct from genes important for the adaptive plastic response observed within a generation. This information is key to obtain a better understanding and prediction of the effects of future increases in both mean and variability of temperatures.
Cold exposure depolarizes cells in insects due to a reduced electrogenic ion transport and a gradual increase in extracellular K
+
concentration (K
+
). Cold-induced depolarization is linked to cold ...injury in chill-susceptible insects, and the locust, Locusta migratoria, has been shown to improve cold tolerance following cold acclimation through depolarization resistance. Here we investigate how cold acclimation influences depolarization resistance and how this resistance relates to improved cold tolerance. To address this question, we investigated if cold acclimation affects the electrogenic transport capacity and/or the relative K
+
permeability during cold exposure by measuring membrane potentials of warm- and cold-acclimated locusts in the presence and absence of ouabain (Na
+
-K
+
pump blocker) or 4-aminopyridine (4-AP; voltage-gated K
+
channel blocker). In addition, we compared the membrane lipid composition of muscle tissue from warm- and cold-acclimated locust and the abundance of a range transcripts related to ion transport and cell injury accumulation. We found that cold-acclimated locusts are depolarization resistant due to an elevated K
+
permeability, facilitated by opening of 4-AP-sensitive K
+
channels. In accordance, cold acclimation was associated with an increased abundance of Shaker transcripts (gene encoding 4-AP-sensitive voltage-gated K
+
channels). Furthermore, we found that cold acclimation improved muscle cell viability following exposure to cold and hyperkalemia even when muscles were depolarized substantially. Thus cold acclimation confers resistance to depolarization by altering the relative ion permeability, but cold-acclimated locusts are also more tolerant to depolarization.
English abstract: This article has a double focus. First, and in line with the special theme of this issue, it will address and discuss the celebrated, later rebuked and finally almost forgotten ...‘hero’ from our discipline’s historical cabinet of curiosity, the Dutch phenomenologist of religion and theologian, Gerardus van der Leeuw (1890-1950). Van der Leeuw’s work had its primary impact in the first part of the 20th century, but came to play a special role in Denmark when his Introduction to the Phenomenology of Religion was published in Danish in 1969 – a book which influenced a whole generation of Danish high school teachers. Second, taking my departure from van der Leeuws emphasis, I reevaluate the concept of mana in order to explore its relevance in the contemporary, academic study of religion. My point of departure is, that we need a concept covering broad notions of force. Further I argue that a rejuvenated notion of mana should build upon results from the cognitive sciences regarding causal representation as well as from the notion of force-dynamic representations argued in cognitive linguistics. Finally, in a more speculative manner, I shall present a number of hypotheses concerning the relation between social organization and mana and argue that this relation can be understood as a driving factor in a general history of religion. Dansk resume: Denne artikels formål er dobbelt. For det første vil den, i tråd med dette nummers overordnede tema, diskutere en hyldet, udskældt og nu nærmest glemt ’helt’ fra det forskningshistoriske raritetskabinet, den hollandske religionsfænomenolog og teolog, Gerardus van der Leeuw (1890-1950). Van der Leeuw havde sit virke i første halvdel af det 20. århundrede, men fik en særlig i indflydelse i Danmark fra 1969, hvor hans indføring i religionsfænomenologien udkom på dansk under titlen Mennesket og Mysteriet – en bog, som fik stor indflydelse på en hel generation gymnasielærere. For det andet vil den, med afsæt i van der Leeuws brug af mana som central eksplanatorisk kategori, revurdere dette begreb for at undersøge dets relevans for den moderne religionsvidenskab. Udgangspunktet er, at religionsvidenskaben har brug for et begreb, der dække kraftforestillinger bredt forstået, og at nyere kognitive forklaringer på kausale forestillinger samt den kognitive lingvistiks fokus på kraftdynamik i sproget kan fungere som udgangspunkt for et moderne mana-begreb. Afslutningsvis vil artiklen mere spekulativt udkaste en række hypoteser om forholdet mellem social organisering og mana som en central drivkraft i den generelle religionshistorie.
To determine the prevalence of residual β-cell function (RBF) in children after 3-6 years of type 1 diabetes, and to examine the association between RBF and incidence of severe hypoglycemia, glycemic ...control, and insulin requirements.
A total of 342 children (173 boys) 4.8-18.9 years of age with type 1 diabetes for 3-6 years were included. RBF was assessed by testing meal-stimulated C-peptide concentrations. Information regarding severe hypoglycemia within the past year, current HbA1c, and daily insulin requirements was retrieved from the medical records and through patient interviews.
Ninety-two children (27%) had RBF >0.04 nmol/L. Patients with RBF <0.04 nmol/L were significantly more likely to have severe hypoglycemia than patients with RBF >0.04 nmol/L (odds ratio, 2.59; 95% CI, 1.10-7.08; P < 0.03). HbA1c was significantly higher in patients with RBF <0.04 nmol/L compared with patients with RBF >0.04 nmol/L (mean, 8.49 ± 0.08% 69.3 ± 0.9 mmol/mol vs. 7.92 ± 0.13% 63.1 ± 1.4 mmol/mol; P < 0.01), and insulin requirements were significantly lower in patients with RBF >0.2 nmol/L (mean ± SE: 1.07 ± 0.02 vs. 0.93 ± 0.07 units/kg/day; P < 0.04).
We demonstrated considerable phenotypic diversity in RBF among children after 3-6 years of type 1 diabetes. Children with RBF are at lower risk for severe hypoglycemia, have better diabetes regulation, and have lower insulin requirements compared with children without RBF. There appears to be a lower limit for stimulated RBF of ∼0.04 nmol/L that confers a beneficial effect on hypoglycemia and metabolic control.
Low temperatures limit the distribution and abundance of ectotherms. However, many insects can survive low temperatures by employing one of two cold tolerance strategies: freeze avoidance or freeze ...tolerance. Very few species can employ both strategies, but those that do provide a rare opportunity to study the mechanisms that differentiate freeze tolerance and freeze avoidance. We showed that overwintering pupae of the cabbage white butterfly Pieris rapae can be freeze tolerant or freeze avoidant. Pupae from a population of P. rapae in northeastern Russia (Yakutsk) froze at c. −9.3 °C and were freeze-tolerant in 2002–2003 when overwintered outside. However, P. rapae from both Yakutsk and southern Canada (London) acclimated to milder laboratory conditions in 2014 and 2017 froze at lower temperatures (< −20 °C) and were freeze-avoidant. Summer-collected P. rapae larvae (collected in Yakutsk in 2016) were partially freeze-tolerant, and decreased the temperature at which they froze in response to starvation at mild low temperatures (4 °C) and repeated partial freezing events. By comparing similarly-acclimated P. rapae pupae from both populations, we identified molecules that may facilitate low temperature tolerance, including the hemolymph ice-binding molecules and several potential low molecular weight cryoprotectants. Pieris rapae from Yakutsk exhibited high physiological plasticity, accumulating cryoprotectants and almost doubling their hemolymph osmolality when supercooled to −15 °C for two weeks, while the London P. rapae population exhibited minimal plasticity. We hypothesize that physiological plasticity is an important adaptation to extreme low temperatures (i.e. in Yakutsk) and may facilitate the transition between freeze avoidance and freeze tolerance.
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•Pieris rapae can be either freeze tolerant or freeze avoidant.•Cold tolerance strategy varied with developmental stage, population and acclimation.•P. rapae from an extreme climate (Siberia) exhibited high metabolomic plasticity.•Cryoprotectants and ice-binding agents may facilitate extreme cold tolerance.
Insects are mass-reared for release for biocontrol including the sterile insect technique. Insects are usually reared at temperatures that maximize the number of animals produced, are chilled for ...handling and transport, and released into the field, where temperatures may be considerably different to those experienced previously. Insect thermal biology is phenotypically plastic (i.e. flexible), which means that there may exist opportunities to increase the performance of these programmes by modifying the temperature regimes during rearing, handling, and release. Here we synthesize the literature on thermal plasticity in relation to the opportunities to reduce temperature-related damage and increase the performance of released insects. We summarize how and why temperature affects insect biology, and the types of plasticity shown by insects. We specifically identify aspects of the production chain that might lead to mismatches between the thermal acclimation of the insect and the temperatures it is exposed to, and identify ways to harness physiological plasticity to reduce that potential mismatch. We address some of the practical (especially engineering) challenges to implementing some of the best-supported thermal regimes to maximize performance (e.g. fluctuating thermal regimes), and acknowledge that a focus only on thermal performance may lead to unwanted trade-offs with other traits that contribute to the success of the programme. Together, it appears that thermal physiological plasticity is well-enough understood to allow its implementation in release programmes.
We studied the food quality of the aphid Rhopalosiphum padi to the pirate bug Orius majusculus using Ephestia eggs as high‐quality comparison prey. Several performance parameters were tested on ...individuals that had been reared and maintained on each of the two single‐prey diets or on a mixed diet. All fitness parameters were lower in individuals fed aphids only, indicating poor food quality of this prey. Compared with the pure Ephestia egg diet, the mixed diet enhanced teneral mass, while adult survival and female starvation tolerance were negatively affected and all other traits were unaffected. Body protein proportions were constant across diets, whereas lipid proportion was low in the aphid treatment. Preference for aphids was lower following a monotypic aphid diet than when reared on Ephestia eggs or a mixed diet. The results confirm that R. padi is low‐quality food for O. majusculus as it is for other generalist predators, even though O. majusculus may contribute significantly to population suppression of the aphid.
Means and variances of the environmental thermal regime play an important role in determining the fitness of terrestrial ectotherms. Adaptive phenotypic responses induced by heterogeneous ...temperatures have been shown to be mediated by molecular pathways independent of the classic heat shock responses; however, an in-depth understanding of plasticity induced by fluctuating temperatures is still lacking. We investigated high and low temperature acclimation induced by fluctuating thermal regimes at two different mean temperatures, at two different amplitudes of fluctuation and across the developmental and adult life stages of
For developmental acclimation, we found mildly detrimental effects of high-amplitude fluctuations for critical thermal minima, while the critical thermal maxima showed a beneficial response to higher amplitude fluctuations. For adult acclimation involving shifts between fluctuating and constant regimes, cold tolerance was shown to be dictated by developmental temperature conditions irrespective of the adult treatments, while the acquired heat tolerance was readily lost when flies developed at fluctuating temperature were shifted to a constant regime as adults. Interestingly, we also found that the effect of fluctuations at any life stage was gradually lost with prolonged adult maintenance, suggesting a more prominent effect of fluctuations during developmental compared with adult acclimation in
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