Hsp70 and lipid peroxide levels following heat stress in Xeropicta derbentina (Krynicki 1836) (Gastropoda,Pulmonata) with regard to different colour morphs

Terrestrial snails which live under dry and hot conditions need efficient mechanisms of adaptation to counteract the problems of desiccation and over-heating. A profoundly heat tolerant snail species is the Mediterranean Xeropicta derbentina, exhibiting different shell colour morphs ranging from pale white to darkly banded. Considering that dark-pigmented snails are believed to have a disadvantage due to faster heating, we investigated possible differences in the stress markers Hsp70 and lipid peroxideation between four pre-defined colour morphs which were exposed to different temperatures for eight hours. The highest Hsp70 levels were observed in response to 38-40 °C. Levels decreased when this temperature was exceeded. Snails of a pre-defined colour category 3 (with a large black band at the umbilicus side of the shell) showed the most prominent Hsp70 response. Lipid peroxideation levels also showed a maximum at 38 °C but displayed a second peak at rather high temperatures at which the Hsp70 level already had decreased (45-48 °C). Particularly pure white snails (category 1) and the most pigmented ones (category 4) were found to have different levels of lipid peroxidation at 38 °C and 45 °C compared to the other morphs. A hypothesis involving a combined two-phase defence mechanism, to which both, the Hsp70 protection system and the antioxidant defence system, may contribute, is discussed.     

Effects of Temperature on Resistance in Phaseolus vulgaris Genotypes and on Development of Meloidogyne Species

Phaseolus vulgaris lines with heat-stable resistance to Meloidogyne spp. may be needed to manage root-knot nematodes in tropical regions. Resistance expression before and during the process of nematode penetration and development in resistant genotypes were studied at pre- and postinoculation temperatures of 24 °C and 24 °C, 24 °C and 28 °C, 28 °C and 24 °C, and 28 °C and 28 °C. Resistance was effective at all temperature regimes examined, with fewer nematodes in roots of a resistant line compared with a susceptible line. Preinoculation temperature did not modify resistance expression to later infections by root-knot nematodes. However, postinoculation temperatures affected development of Meloidogyne spp. in both the resistant and susceptible bean lines tested. The more rapid development of nematodes to adults at the higher postinoculation temperature of 28 °C in both bean lines suggests direct temperature effects on nematode development instead of on resistance expression of either of two gene systems. Also, resistance was stable at 30 °C and 32 °C.     

Subtropical mouse-tailed bats use geothermally heated caves for winter hibernation

We report that two species of mouse-tailed bats (Rhinopoma microphyllum and R. cystops) hibernate for five months during winter in geothermally heated caves with stable high temperature (20°C). While hibernating, these bats do not feed or drink, even on warm nights when other bat species are active. We used thermo-sensitive transmitters to measure the bats’ skin temperature in the natural hibernacula and open flow respirometry to measure torpid metabolic rate at different ambient temperatures (T_a, 16–35°C) and evaporative water loss (EWL) in the laboratory. Bats average skin temperature at the natural hibernacula was 21.7 ± 0.8°C, and no arousals were recorded. Both species reached the lowest metabolic rates around natural hibernacula temperatures (20°C, average of 0.14 ± 0.01 and 0.16 ± 0.04 ml O₂ g⁻¹ h⁻¹ for R. microphyllum and R. cystops, respectively) and aroused from torpor when T_a fell below 16°C. During torpor the bats performed long apnoeas (14 ± 1.6 and 16 ± 1.5 min, respectively) and had a very low EWL. We hypothesize that the particular diet of these bats is an adaptation to hibernation at high temperatures and that caves featuring high temperature and humidity during winter enable these species to survive this season on the northern edge of their world distribution.     

The Effect of Increasing Water Temperatures on Schistosoma mansoni Transmission and Biomphalaria pfeifferi Population Dynamics: An Agent-Based Modelling Study

Introduction

There is increasing interest in the control and elimination of schistosomiasis. Little is known, however, about the likely effects of increasing water-body temperatures on transmission.

Methods

We have developed an agent-based model of the temperature-sensitive stages of the Schistosoma and intermediate host snail life-cycles, parameterised using data from S. mansoni and Biomphalaria pfeifferi laboratory and field-based observations. Infection risk is calculated as the number of cercariae in the model, adjusted for their probability of causing infection.

Results

The number of snails in the model is approximately constant between 15–31°C. Outside this range, snail numbers drop sharply, and the snail population cannot survive outside the range 14–32°C. Mean snail generation time decreases with increasing temperature from 176 days at 14°C to 46 days at 26°C. Human infection risk is highest between 16–18°C and 1 pm and 6–10 pm in calm water, and 20–25°C and 12–4 pm in flowing water. Infection risk increases sharply when temperatures increase above the minimum necessary for sustained transmission.

Conclusions

The model suggests that, in areas where S. mansoni is already endemic, warming of the water at transmission sites will have differential effects on both snails and parasites depending on abiotic properties of the water-body. Snail generation times will decrease in most areas, meaning that snail populations will recover faster from natural population reductions and from snail-control efforts. We suggest a link between the ecological properties of transmission sites and infection risk which could significantly affect the outcomes of interventions designed to alter water contact behaviour – proposing that such interventions are more likely to reduce infection levels at river locations than lakes, where infection risk remains high for longer. In cooler areas where snails are currently found, increasing temperatures may significantly increase infection risk, potentially leading to new, high-intensity foci of infection.     

Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa

Development times of eggs, larvae and pupae of vectors of onchocerciasis (Simulium spp.) and of Onchocerca volvulus larvae within the adult females of the vectors decrease with increasing temperature. At and above 25°C, the parasite could reach its infective stage in less than 7 days when vectors could transmit after only two gonotrophic cycles. After incorporating exponential functions for vector development into a novel blackfly population model, it was predicted that fly numbers in Liberia and Ghana would peak at air temperatures of 29°C and 34°C, about 3°C and 7°C above current monthly averages, respectively; parous rates of forest flies (Liberia) would peak at 29°C and of savannah flies (Ghana) at 30°C. Small temperature increases (less than 2°C) might lead to changes in geographical distributions of different vector taxa. When the new model was linked to an existing framework for the population dynamics of onchocerciasis in humans and vectors, transmission rates and worm loads were projected to increase with temperature to at least 33°C. By contrast, analyses of field data on forest flies in Liberia and savannah flies in Ghana, in relation to regional climate change predictions, suggested, on the basis of simple regressions, that 13–41% decreases in fly numbers would be expected between the present and before 2040. Further research is needed to reconcile these conflicting conclusions.     

Adaptive phenotypic plasticity and local adaptation for temperature tolerance in freshwater zooplankton

Many organisms have geographical distributions extending from the tropics to near polar regions or can experience up to 30°C temperature variation within the lifespan of an individual. Two forms of evolutionary adaptation to such wide ranges in ambient temperatures are frequently discussed: local adaptation and phenotypic plasticity. The freshwater planktonic crustacean Daphnia magna, whose range extends from South Africa to near arctic sites, shows strong phenotypic and genotypic variation in response to temperature. In this study, we use D. magna clones from 22 populations (one clone per population) ranging from latitude 0° (Kenya) to 66° North (White Sea) to explore the contributions of phenotypic plasticity and local adaptation to high temperature tolerance. Temperature tolerance was studied as knockout time (time until immobilization, T_imm) at 37°C in clones acclimatized to either 20°C or 28°C. Acclimatization to 28°C strongly increased T_imm, testifying to adaptive phenotypic plasticity. At the same time, T_imm significantly correlated with average high temperature at the clones’ sites of origin, suggesting local adaptation. As earlier studies have found that haemoglobin expression contributes to temperature tolerance, we also quantified haemoglobin concentration in experimental animals and found that both acclimatization temperature (AccT) and temperature at the site of origin are positively correlated with haemoglobin concentration. Furthermore, Daphnia from warmer climates upregulate haemoglobin much more strongly in response to AccT, suggesting local adaptation for plasticity in haemoglobin expression. Our results show that both local adaptation and phenotypic plasticity contribute to temperature tolerance, and elucidate a possible role of haemoglobin in mediating these effects that differs along a cold–warm gradient.     

Paramphistomum daubneyi: characteristics of infection in three lymnaeid species

Experimental infections of two South American lymnaeids (Lymnaea neotropica and L. viatrix var. ventricosa) with Paramphistomum daubneyi were carried out to determine if these snail species could sustain larval development of this digenean and, if so, to specify their potential for cercarial production. A French population of Galba truncatula infected and raised according to the same protocol served as controls. In both experiments, prevalence of P. daubneyi infections in snails did not significantly differ from each other. In snail groups evaluated for cercarial shedding (first experiment), a significantly lower number of shed cercariae was noted for L. neotropica, while those from G. truncatula and L. v. ventricosa did not differ significantly from each other. Dissection of infected snails at day 65 post-exposure at 20 °C (second experiment) found significantly lower burdens of P. daubneyi rediae and cercariae in the bodies of L. neotropica than in those of G. truncatula and L. v. ventricosa. Compared to total cercarial production observed in dissected snails, the percentage of cercariae which exited from snails was 75.6% for G. truncatula, 21.6% for L. neotropica, and 91.4% for L. v. ventricosa. This last species seems to be a good candidate for metacercarial production of P. daubneyi.     

Temperature response of photosynthesis in different drug and fiber varieties of Cannabis sativa L.

The temperature response on gas and water vapour exchange characteristics of three medicinal drug type (HP Mexican, MX and W1) and four industrial fiber type (Felinq 34, Kompolty, Zolo 11 and Zolo 15) varieties of Cannabis sativa, originally from different agro-climatic zones worldwide, were studied. Among the drug type varieties, optimum temperature for photosynthesis (T_opt) was observed in the range of 30–35 °C in high potency Mexican HPM whereas, it was in the range of 25–30 °C in W1. A comparatively lower value (25 °C) for T_opt was observed in MX. Among fiber type varieties, T_opt was around 30 °C in Zolo 11 and Zolo 15 whereas, it was near 25 °C in Felinq 34 and Kompolty. Varieties having higher maximum photosynthesis (P_{N max}) had higher chlorophyll content as compared to those having lower P_{N max}. Differences in water use efficiency (WUE) were also observed within and among the drug and fiber type plants. However, differences became less pronounced at higher temperatures. Both stomatal and mesophyll components seem to be responsible for the temperature dependence of photosynthesis (P_N) in this species, however, their magnitude varied with the variety. In general, a two fold increase in dark respiration with increase in temperature (from 20 °C to 40 °C) was observed in all the varieties. However, a greater increase was associated with the variety having higher rate of photosynthesis, indicating a strong association between photosynthetic and respiratory rates. The results provide a valuable indication regarding variations in temperature dependence of P_N in different varieties of Cannabis sativa L.     

Effect of temperature and cycle length on microbial competition in PHB-producing sequencing batch reactor

The impact of temperature and cycle length on microbial competition between polyhydroxybutyrate (PHB)-producing populations enriched in feast-famine sequencing batch reactors (SBRs) was investigated at temperatures of 20 °C and 30 °C, and in a cycle length range of 1–18 h. In this study, the microbial community structure of the PHB-producing enrichments was found to be strongly dependent on temperature, but not on cycle length. Zoogloea and Plasticicumulans acidivorans dominated the SBRs operated at 20 °C and 30 °C, respectively. Both enrichments accumulated PHB more than 75% of cell dry weight. Short-term temperature change experiments revealed that P. acidivorans was more temperature sensitive as compared with Zoogloea. This is particularly true for the PHB degradation, resulting in incomplete PHB degradation in P. acidivorans at 20 °C. Incomplete PHB degradation limited biomass growth and allowed Zoogloea to outcompete P. acidivorans. The PHB content at the end of the feast phase correlated well with the cycle length at a constant solid retention time (SRT). These results suggest that to establish enrichment with the capacity to store a high fraction of PHB, the number of cycles per SRT should be minimized independent of the temperature.     

Interaction of Fusarium oxysporum f. sp. ciceri and Meloidogyne javanica on Cicer arietinum

Interaction of Meloidogyne javanica and Fusarium oxysporum f. sp. ciceri was studied on Fusarium wilt-susceptible (JG 62 and K 850) and resistant (JG 74 and Avrodhi) chickpea cultivars. In greenhouse experiments, inoculation of M. javanica juveniles prior to F. oxysporum f. sp. ciceri caused greater wilt incidence in susceptible cultivars and induced vascular discoloration in roots of resistant cultivars. Nematode reproduction was greatest (P = 0.05) at 25 °C. Number of galls and percentage of root area galled increased when the temperature was increased from 15 °C to 25 °C. Wilt incidence was greater at 20 °C than at 25 °C. Chlorosis of leaves and vascular discoloration of plants did not occur at 15 °C. The nematode enhanced the wilt incidence in wilt-susceptible cultivars only at 25 °C. Interaction between the two pathogens on shoot and root weights was significant only at 20 °C, and F. o. ciceri suppressed the nematode density at this temperature. Wilt incidence was greater in clayey (48% clay) than in loamy sand (85% sand) soils. The nematode caused greater plant damage on loamy sand than on clayey soil. Fusarium wilt resistance in Avrodhi and JG 74 was stable in the presence of M. javanica across temperatures and soil types.     

Influence of Temperature on Multiplication and Egg Hatching of Longidorus africanus

Longidorus africanus multiplication on tomato was highest at 29 °C. Few nematodes were recovered after 6 weeks at soil temperatures of 35 °C or below 23 °C. The time to egg hatching was shortest and the percentage of eggs hatching was highest at 29 °C. The minimum temperature and the heat sum above this temperature required for egg development were calculated to be 14.3 °C and 94.08 degree-days, respectively. The thermal times required for egg development by L. africanus and L. elongatus were nearly identical. For both species the product of the base temperature and the heat sum was near constant, and at a temperature of 22.3 °C the rates of egg development were equal.     

Ditylenchus dipsaci Infestation of Trifolium repens. I. Temperature Effects,Seedling Invasion,and a Field Survey

Rates of development of stem nematode (Ditylenchus dipsaci) in white clover (Trifolium repens) seedlings were found to be linearly related to temperature. Basal developmental temperature (T_b) was 3 °C, and the thermal constant (S) for development of gravid adult females from freshly laid eggs was 270 accumulated day-degrees above the T_b. Only 12% at 20 °C and 4% at 4 °C of the gravid female nematodes inoculated into seedling axils successfully penetrated seedling epidermis. These nematodes slowly migrated within the seedling and after a lag of 5 days at 20 °C started to lay eggs. The maximal rate of egg production was temperature-dependent, being 0.8 and 3.1 eggs female⁻¹ day⁻¹ at 10 and 20 °C, respectively. Nematodes emigrated rapidly from infested stolons when they were immersed in water, with rates being highest at 25 °C and lowest at 4 °C. The sensitivity to temperature of many of the parameters that govern nematode population dynamics indicates that climatic changes will have a marked effect upon this host-parasite system. A study of infested stolons from the field indicated that nematode numbers increased up to 3,000 or more before tissue senesence, triggered by nematode damage, caused a mass emigration of nematodes from the stolon.     

Factors influencing seed germination of medicinal plant Salvia aegyptiaca L. (Lamiaceae)

Salvia aegyptiaca is a xerophytic perennial herb belongs to the Lamiaceae family commonly used for medicinal purposes. Laboratory experiments were carried out to assess the effects of temperature and salinity on seed germination and recovery responses after transferring to distilled water. Temperatures between 10 and 40 °C seem to be favourable for the germination of this species. Germination was inhibited by either an increase or decrease in temperature from the optimum (30 °C). The highest germination percentages were obtained at 0 mM NaCl; however, the increase of solution osmolalities progressively inhibited seed germination. The germination rate decreased with an increase in salinity for most of tested temperatures, but comparatively higher rates were obtained at 30 °C. Salt stress decreased both the percentage and the rate of germination. An interaction between salinity and temperature yielded no germination at 300 mM NaCl. By experimental transfer to distilled water, S. aegyptiaca seeds that were exposed to moderately saline conditions recovered and keep their ability to germinate mostly at low temperatures. At 300 mM NaCl, germination recovery decreased with increasing temperature and it was completely inhibited at 40 °C.     

Temperature Effects on the Attachment of Pasteuria penetrans Endospores to Meloidogyne arenaria Race 1

Pasteuria penetrans is a gram positive bacterium that prevents Meloidogyne spp. from reproducing and diminishes their ability to penetrate roots. The attachment of the endospores to the cuticle of the nematodes is the first step in the life cycle of the bacterium and is essential for its reproduction. As a preliminary study to a field solarization test, the effects of temperature on the attachment of P. penetrans on Meloidogyne arenaria race 1 were investigated. Preexposing second-stage juveniles (J2) of M. arenaria to approximately 30 °C in water before exposing them to endospores increased their receptivity to endospore attachment when compared to treating J2 at 25 °C or 35 °C. In tests with soil, highest attachment occurred when J2 were incubated in soil infested with endospores and maintained at 20 °C to 30 °C for 4 days. Heating J2 in soil to sublethal temperatures (35 °C to 40 °C) decreased endospore attachment. Incubating P. penetrans endospores in soil at 30 °C to 70 °C for 5 hours a day over 10 days resulted in reductions of endospore attachment to nematodes as temperatures of incubation increased to 50 °C and higher.     

Effect of Conditioning Treatments on the Survival of Radopholus similis at High Temperatures

Heat treatments are an environmentally safe method for eliminating quarantine pests from tropical foliage. Conditioning heat treatments can induce thermotolerance against subsequent and otherwise phytotoxic temperatures in tropical foliage, allowing heat treatments to be even more effective. However, if thermotolerance is also induced in nematodes of quarantine significance like Radopholus similis, heat treatments would be rendered ineffective. A lethal thermal death point (LT_99.9) was established for R. similis by recording mortality at 25 (control temperature), 43°C, 45°C, 47°C, or 49°C after a 0, 1-, 2-, 4-, 6-, 8-, 10-, 12-, or 15-minute exposure. In a second experiment, nematodes were conditioned at 35, 40, or 45°C for 0, 15, 30, 60, 120, and 180 minutes, allowed to rest for 3 hours, and then challenged at 47°C for 5 minutes. No nematodes survived the challenge heat treatment; rather, nematode mortality was hastened by the conditioning treatment itself. In a third experiment, R. similis inside anthurium roots were conditioned at 25°C or 40°C for 15 minutes and then treated at 45°C for up to 8 minutes. Mortality of conditioned and unconditioned nematodes was similar (P > 0.1). Conditioning treatments increase plant thermotolerance but do not induce thermotolerance in R. similis. Heat treatments have promise as disinfection protocols for quarantines.     

Temperature-Dependent Development of Pasteuria penetrans in Meloidogyne arenaria

Pasteuria penetrans is a promising biological control agent of plant-parasitic nematodes. This study was conducted to determine effects of temperature on the bacterium''s development in Meloidogyne arenaria. Developmental stages of P. penetrans were viewed with a compound microscope and verified with scanning electron microscopy within each nematode at 100 accumulated degree-day intervals by tracking accumulated degree-days at three temperatures (21, 28, and 35 °C). Five predominant developmental stages of P. penetrans were identified with light microscopy: endospore germination, vegetative growth, differentiation, sporulation, and maturation. Mature endospores were detected at 28, 35, and >90 calendar days at 35, 28, and 21 °C, respectively. The number of accumulated degree-days required for P. penetrans to reach a specific developmental stage was different for each temperature. Differences were observed in the development of P. penetrans at 21, 28, and 35 °C based on regression values fitted for data from 100 to 600 accumulated degree-days. A linear response was observed between 100 to 600 accumulated degree-days; however, after 600 accumulated degree-days the rate of development of P. penetrans leveled off at 21 and 28 °C, whereas at 35 °C the rate decreased. Results suggest that accumulated degree-days may be useful only in predicting early-developmental stages of P. penetrans.     

Warming reduces metabolic rate in marine snails: adaptation to fluctuating high temperatures challenges the metabolic theory of ecology

The universal temperature-dependence model (UTD) of the metabolic theory of ecology (MTE) proposes that temperature controls mass-scaled, whole-animal resting metabolic rate according to the first principles of physics (Boltzmann kinetics). Controversy surrounds the model''s implication of a mechanistic basis for metabolism that excludes the effects of adaptive regulation, and it is unclear how this would apply to organisms that live in fringe environments and typically show considerable metabolic adaptation. We explored thermal scaling of metabolism in a rocky-shore eulittoral-fringe snail (Echinolittorina malaccana) that experiences constrained energy gain and fluctuating high temperatures (between 25°C and approximately 50°C) during prolonged emersion (weeks). In contrast to the prediction of the UTD model, metabolic rate was often negatively related to temperature over a benign range (30–40°C), the relationship depending on (i) the temperature range, (ii) the degree of metabolic depression (related to the quiescent period), and (iii) whether snails were isolated within their shells. Apparent activation energies (E) varied between 0.05 and −0.43 eV, deviating excessively from the UTD''s predicted range of between 0.6 and 0.7 eV. The lowering of metabolism when heated should improve energy conservation in a high-temperature environment and challenges both the theory''s generality and its mechanistic basis.