Effect of temperature on germination,growth, and infectivity of the mosquito pathogen Tolypocladium cylindrosporum (deuteromycotina; hyphomycetes)

The mosquito pathogen Tolypocladium cylindrosporum was examined with regard to its response to temperature. Similar temperature ranges were found for growth, germination, and infectivity of blastospores and conidia. Germination occurred at 8° and 33°C but not at 6° and 35°C. Optimal germination and growth was noted between 24° and 27°C for both spore types. Infectivity of blastospores and conidia at different temperatures was examined by exposing L₂Aedes sierrensis larvae to concentrations of 5 × 10⁵ blastospores/ml or 5 × 10⁶ conidia/ml. Larvae were incubated at 12°, 15°, 25°, and 30°C. Infection occurred at all temperatures tested with LT₅₀ values ranging from 22.7 days (12°C) to 5.6 (25°C) days for conidia and 4.7 days (12°C) to 0.6 day (25°C) for blastospores. These results confirmed earlier findings that blastospores infected and killed host larvae more rapidly than conidia and suggested that this difference is largely due to the more rapid germination rate of blastospores. These experiments demonstrated that T. cylindrosporum can be active against mosquito larvae over a broad range of temperatures encompassing both the cold-water habitat of certain temperate mosquito species as well as the habitat of tropical vector species.     

The importance of fluctuating thermal regimes for repairing chill injuries in the tropical beetle Alphitobius diaperinus (Coleoptera: Tenebrionidae) during exposure to low temperature

Abstract. In this study, the impact of acclimation (1 month at 15 °C vs. breeding at 30 °C) and fluctuating thermal regimes (daily transfers from low temperatures to various higher temperatures for 2 h) on the cold tolerance of the tropical beetle, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae) was examined. Acclimation increased significantly the duration of survival (Lt₅₀) at a constant 5 °C (7.7 ± 0.3 days to 9.7 ± 0.5 days). Survival of acclimated and nonacclimated beetles increased slightly at alternating temperatures of 5 °C/10 °C or 5 °C/15 °C. When daily transfer to 20 °C was applied, survival (Lt₅₀) was improved markedly (nonacclimated: 15.5 ± 0.7 days, acclimated: 19.6 ± 0.6 days). The higher temperatures may allow progressive repair of injuries, and the effects of chilling may be repaired completely at 25 and 30 °C, a phenomenon recorded here for the first time. It is estimated that the theoretical upper threshold of chill injury (Th) of nonacclimated beetles is 15.1 °C whereas it is shifted down to 11.2 °C in acclimated beetles, which might enable this temperature to allow effective repair of injury.     

Survival of cabbage stem flea beetle larvae,Psylliodes chrysocephala,exposed to low temperatures

The cabbage stem flea beetle, Psylliodes chrysocephala (L.) (Coleoptera: Chrysomelidae), is a major pest of winter oilseed rape. The larvae live throughout winter in leaf petioles and stems. Winter temperatures might play an important role in survival during winter and hence population dynamics, yet to what degree is unknown. This study investigates the effect of exposure time, cold acclimation, and larval stage on survival at ?5 and ?10 °C. Exposure time at ?5 °C was 1, 2, 4, 8, 12, 16, and 20 days and 6, 12, 24, 36, 48, 72, 96, 120, and 144 h at ?10 °C. Mortality increased with increasing exposure time and was significantly lower for cold‐acclimated larvae. Estimated time until an expected mortality of 50% (LT₅₀) and 90% (LT₉₀) of larvae exposed to ?5 °C was 7.4 and 9.6 days (non‐acclimated) and 11.0 and 15.1 days (acclimated), respectively. Estimated LT₅₀ for non‐acclimated and acclimated larvae exposed to ?10 °C was 32.6 and 70.5 h, respectively, and estimated LT₉₀ 66.8 and 132.2 h. Significant differences in mortality between larval stages were observed only at ?5 °C. When exposed to ?5 °C for 8 days, mortality of first and second instars was 81.2 and 51.3%, respectively. When exposed to ?10 °C for 2 days, mortality of first and second instars was 70.5 and 76.1%. Data on winter temperatures in Denmark from 1990 to 2013 showed that larvae were rarely exposed to a number of continuous days at ?5 or ?10 °C causing a potential larval mortality of 50–90%.     

Temperature-dependent development, diapause and cold tolerance of Gratiana graminea, a potential biological control agent of Solanum viarum in Florida, USA

The objectives of this study were to examine temperature-dependent development, diapause and cold tolerance of Gratiana graminea Klug (Chrysomelidae), a candidate biological control agent of tropical soda apple, Solanum viarum Dunal (Solanaceae). Immature development was examined at six constant temperatures ranging from 15°C to 30°C. Diapause induction was determined by exposing adults to either long or short photoperiods at 20°C and cold tolerance was assessed by exposing adults to 0°C. G. graminea completed development at temperatures ranging from 20°C to 30°C. Linear regression estimated a lower temperature threshold of 11.7°C and 312 degree-days were required to complete development. Diapause was induced when adults were exposed to short photoperiods (10:14 L:D h) at 20°C. The lethal times for diapausing adults of G. graminea at 0°C (LT₅₀?=?19?days, LT₉₀?=?41?days) were two times higher compared to Gratiana boliviana Spaeth, a biological control agent already established in south and central Florida, USA. The presence of diapause and the greater cold tolerance suggest that G. graminea may establish and perform better than G. boliviana in northern Florida.     

Impact of different acclimation temperatures and duration on the chill coma temperature and oxygen consumption in the tenebrionid beetle Alphitobius diaperinus

When the ambient temperature is lowered to an insect's lower thermal limit, the insect enters into chill coma. Chill coma temperature and chill coma recovery can vary within species as a result of thermal acclimation, although the physiological basis of the onset of chill coma remains poorly understood. The present study investigates how the temperature of acclimation (0, 5, 10, 15 and 20 °C for 2 or 7 days) affects chill coma temperature and oxygen consumption in adult Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae). It is hypothesized that the threshold decline in metabolic rate corresponds to the entry into chill coma. Oxygen consumption (as a proxy of metabolism) is measured across the chill coma temperature threshold, and a strong decline in oxygen consumption is expected at entry into chill coma. The acclimation decreases the chill coma temperature significantly from 6.6 ± 1.1 °C in control insects to 3.1 ± 0.7 °C in those acclimated to 10 °C. The change in metabolic rate (Q₁₀) after acclimation to temperatures ranging from 10 to 20 °C is 3.7. Despite acclimation, the metabolic rate of A. diaperinus conforms to Arrhenius kinetics, suggesting that the response of this beetle does not show metabolic compensation. The data suggest the existence of a threshold decline in metabolic rate during cooling that coincides with the temperature at which an insect goes into chill coma.     

The role of temperature in enhancing the insecticidal activity of Bacillus thuringiensis against Spodoptera littoralis larvae

The present study scrutinised how far temperature would affect the velocity of the insecticidal activity of Bacillus thuringiensis, as the rapidity of pest control achievements is of a great concern. Third instar Spodoptera littoralis larvae were treated with Bt at three concentration levels under five different temperatures (15°C, 20°C, 25°C, 30°C and 35°C). LT₅₀s were evaluated in each case. The LT₅₀ values showed various levels of reductions as temperature and/or Bt concentration increased, indicating that the velocity of mortality (1/LT₅₀) and/or the rapidity of Bt activity was almost temperature dependant. However, relatively high and low reduction percentages in the LT₅₀ values on the elevation of 5°C were obtained at lower and higher temperature ranges, respectively. The temperature coefficient, Q ₁₀ values, determined within narrow ranges (5°C) showed great reductions when temperature increased from 15°C to 20°C at all Bt concentrations. Raising temperature by 5°C above 20°C or 25°C almost caused similar Q ₁₀ values indicating constant increase in the response of Bt activity within 20–30°C temperature range. Q ₁₀ values over 30°C were comparatively very low. This proved that decrease in Q ₁₀ values due to the rise of temperature was dependant on the starting temperature.     

Effect of nuclear polyhedrosis virus inNeodiprion sertifer (Geoffr.) [Hymenoptera: Diprionidae] at different temperatures

Larvae ofNeodiprion sertifer (Geoff.) were reared on twigs from Scots pine at three different temperatures, 12°C, 18°C and 24°C. The LT₅₀ of virus-infected larvae was 19.3, 9.5 and 4,6 days respectively. In the control the median length of the larval period was 45.7, 29.8 and 22.1 days at the same temperatures. From this results it is concluded that both the LT₅₀ and the length of the larval period are prolonged by low temperature. The medium length of the larval period, however, is relatively more prolonged than is the LT₅₀. Therefore, nuclear polyhedrossis virus may be an effective control agent againstN. sertifer in cool areas even if the LT₅₀ is relatively long.     

Induced expression of the class II chitinase gene during cold acclimation and dehydration of bermudagrass (Cynodon sp.)

Bermudagrass cultivars vary greatly in their ability to survive freezing temperatures as a result of a differential ability to cold acclimate (CA) at temperatures slightly above 0°C. Little information exists on the genetic and physiological mechanisms associated with the cold acclimation process in bermudagrass. Experiments were conducted to study the changes in chitinase gene expression during cold acclimation of freeze-tolerant bermudagrass cultivars. A chitinase gene (CynCHT1) was isolated from ’Midiron’ bermudagrass. Because the hydrophilic protein putatively encoded by the gene lacked an N-terminal cysteine-rich domain and a hydrophobic C-terminal extension, it was classified a class II chitinase. The expression patterns of this and related chitinase genes in response to CA, drought, and ABA were investigated in freeze-tolerant ’MSU’ (LT₅₀=?11°C), Midiron (LT₅₀=?10°C) and ’Uganda’ (LT₅₀=?8°C) bermudagrasses. Northern-blot analysis indicated expression in the crown tissues induced by CA at 8°C/2°C day/night temperature cycles. Induction of gene expression was evident in tissues sampled at 2 and 28 days after initiating CA. Expression after 2-days de-acclimation at 28°C/24°C was similar to control levels. Significantly higher levels of CA-induced chitinase gene expression were observed in MSU and Midiron, compared to Uganda. Similar expression patterns were observed among the cultivars in responses to drought and ABA. These results suggest that chitinases have important roles in bermudagrass response to low temperature and dehydration stresses.     

Influence of temperature on the biological parameters of the anholocyclic species Cinara tujafilina (Hemiptera: Aphidoidea)

Aphids are a good model to study insect reaction to habitat change. Temperature is one of the main factors that influences insects. This paper examines the influence of temperature on developmental stages, fecundity, survival rate and demographic parameters of Cinara tujafilina (Hemiptera: Aphidoidea, Lachnidae), connected with decorative plants of the Cupressaceae family. C. tujafilina was reared in a laboratory on T. orientalis at five constant temperatures of 10, 15, 20, 25 and 28°C, 70% humidity and 14L:10D. The pre-reproduction stage varied from 7 at 25°C to 19 days at 10°C. Developmental threshold was assigned at 3.5°C. The longest reproduction stage for the aphids developing was recorded at 25°C, namely 33 days, while the shortest, at the temperature of 10°C, lasted 8 days. At 25°C this species is characterised by the shortest pre-reproduction stage, the highest fecundity, the highest survival rate and the highest demographic parameters, particularly r_m (0.17). The results suggest that the optimal temperature for the species is 25°C, and indicate that climatic change will favourably influence its development and increase its role as a pest of decorative plants.     

Thermal dependence of clearance and metabolic rates in slow- and fast-growing spats of manila clam Ruditapes philippinarum

Thermal dependence of clearance rate (CR: l h^?1), standard (SMR: J h^?1) and routine metabolic rates (RMR: J h^?1), were analyzed in fast (F)- and slow (S)-growing juveniles of the clam Ruditapes philippinarum. Physiological rates were measured at the maintenance temperature (17 °C), and compared with measurements performed at 10 and 24 °C after 16 h and 14 days to analyze acute and acclimated responses, respectively. Metabolic rates (both RMR and SMR) differed significantly between F and S seeds, irrespective of temperature. Mass-specific CRs were not different for F and S seeds but were significantly higher in F clams for rates standardized according to allometric size-scaling rules. Acute thermal dependency of CR was equal for F and S clams: mean Q ₁₀ were ≈3 and 2 in temperature ranges of 10–17 and 17–24 °C, respectively. CR did not change after 2 weeks of acclimation to temperatures. Acute thermal effects on SMR were similar in both groups (Q ₁₀ ≈ 1 and 1.6 in temperature ranges of 10–17 and 17–24 °C, respectively). Large differences between groups were found in the acute thermal dependence of RMR: Q ₁₀ in F clams (≈1.2 and 1.9 at temperature ranges of 10–17 and 17–24 °C, respectively) were similar to those found for SMR (Q ₁₀ = 1.0 and 1.7). In contrast, RMR of S clams exhibited maximum thermal dependence (Q ₁₀ = 3.1) at 10–17 °C and become depressed at higher temperatures (Q ₁₀ = 0.9 at 17–24 °C). A recovery of RMR in S clams was recorded upon acclimation to 24 °C. Contrasting metabolic patterns between fast and slow growers are interpreted as a consequence of differential thermal sensitivity of the fraction of metabolism associated to food processing and assimilation.     

Time-course for attainment and reversal of acclimation to constant temperature in two Ceratitis species

Acclimation in the thermal tolerance range of insects occurs when they are exposed to novel temperatures in the laboratory. In contrast to the large number of studies that have tested for the ability of insects to acclimate, relatively few have sought to determine the time-course for attainment and reversal of thermal acclimation. In this study the time required for the Mediterranean fruit fly, Ceratitis capitata Wiedemann, and the Natal fruit fly, Ceratitis rosa Karsch, to acclimate to a range of constant temperatures was tested by determining the chill-coma recovery time and heat knock-down time of flies that had been exposed to novel benign temperatures for different durations. The time required for reversal of acclimation for both Ceratitis species was also determined after flies had been returned to the control temperature. Acclimation to 31 °C for only one day significantly improved the heat knock-down time of C. capitata, but also led to slower recovery from chill-coma. Heat knock-down time indicated that acclimation was achieved after only one day in C. rosa, but it took three days for C. rosa to exhibit a significant acclimation response to a novel temperature of 33 °C when measured using chill-coma recovery time. Reversal of acclimation after return to initial temperature conditions was achieved after only one day in both C. capitata and C. rosa. Adult C. capitata held at 31.5 °C initially exhibited improved heat knock-down times but after 9 days the heat knock-down time of these flies had declined to levels not significantly different from that of control flies held at the baseline temperature of 24 °C. In both Ceratitis species, heat knock-down time declined with age whereas chill-coma recovery time increased with age, indicating an increased susceptibility to high and low temperatures, respectively.     

Effect of latitude and acclimation on the lethal temperatures of the peach‐potato aphid Myzus persicae

• 1 Aphids, similar to all insects, are ectothermic and, consequently, are greatly affected by environmental conditions. The peach potato aphid Myzus persicae (Sulzer) has a global distribution, although it is not known whether populations display regional adaptations to distinct climatic zones along its distribution and vary in their ability to withstand and acclimate to temperature extremes. In the present study, lethal temperatures were measured in nine anholocyclic clones of M. persicae collected along a latitudinal cline of its European distribution from Sweden to Spain. The effects of collection origin and intra‐ and intergenerational acclimation on cold and heat tolerance, as determined by upper and lower lethal temperatures (ULT₅₀ and LLT₅₀, respectively), were investigated.
• 2 Lethal temperatures of M. persicae were shown to be plastic and could be altered after acclimation over just one generation. Lower lethal temperatures were significantly depressed in eight of nine clones after acclimation for one generation at 10°C (range: ?13.3 to ?16.2°C) and raised after acclimation at 25°C (range: ?10.7 to ?11.6°C) compared with constant 20°C (range: ?11.9 to ?12.9°C). Upper lethal temperatures were less plastic, although significantly increased after one generation at 25°C (range: 41.8–42.4°C) and in five of nine clones after acclimation at 10°C. There was no evidence of intergenerational acclimation over three generations.
• 3 Thermal tolerance ranges were expanded after acclimation at 10 and 25°C compared with constant 20°C, resulting in aphids reared at 10°C surviving over a temperature range that was approximately 2–6°C greater than those reared at 25°C.
• 4 There was no clear relationship between lethal temperatures and latitude. Large scale mixing of clones may occur across Europe, thus limiting local adaption in thermal tolerance. Clonal type, as identified by microsatellite analysis, did show a relationship with thermal tolerance, notably with Type O clones being the most thermal tolerant. Clonal types may respond independently to climate change, affecting the relative proportions of clones within populations, with consequent implications for biodiversity and agriculture.

     

Low substrate temperature imposes higher limitation to photosynthesis of orange plants as compared to atmospheric chilling

The aim of this study was to evaluate the effects of low air temperature during nocturnal (T_N) and diurnal (T_D) periods as well as the substrate temperature (T_S) on photosynthesis of ‘Valencia’ orange tree grafted on Rangpur lime rootstock. The experiment was carried out in a growth chamber with seven-month-old plants. The plants were exposed to the following temperature regimes: low substrate temperature (LTS, with: T_D = 28°C, T_N = 20°C, T_S = 10°C); low air temperature during night (LT_N, with: T_D = 28°C, T_N = 10°C, T_S = 26°C); low temperature during nighttime and also low substrate temperature (LT_SN, with: T_D = 28°C, T_N = 10°C, T_S = 10°C); low air temperature during both diurnal and nocturnal periods (LT_ND, with: T_D = 17°C, T_N = 10°C, T_S = 26°C); and finally to low air temperature (night and day) and low substrate temperature (LT_SND, with: T_D = 17°C, T_N = 10°C, T_S = 10°C). As reference (control), plants were subjected to T_D = 28°C, T_N = 20°C, and T_S = 26°C. Measurements of leaf gas exchange, photochemical activity and carbohydrate concentrations were performed after six days of exposure to each thermal treatment. Compared to the control, all thermal regimes caused reductions in photosynthesis due to diffusive and metabolic limitations. The photoinhibition was transient in plants exposed to night and substrate low temperatures, whereas it was severe and chronic in plants subjected to chilling during the diurnal period. However, the lowest photosynthesis was observed in plants with low substrate temperature of 10°C (in LT_S, LT_SND and LT_SN treatments), regardless of air temperature. The occurrence of cold night and/or its combination with low substrate temperature caused accumulation of starch in leaves. When considering carbohydrate concentrations in stems and roots, it was not possible to establish a clear response pattern to chilling. In conclusion, the low substrate temperature causes a greater reduction of CO₂ assimilation in citrus plants as compared to the occurrence of low air temperature, being such response a consequence of diffusive and biochemical limitations.     

Dehydrin, alcohol dehydrogenase, and central metabolite levels are associated with cold tolerance in diploid strawberry (Fragaria spp.)

The use of artificial freezing tests, identification of biomarkers linked to or directly involved in the low-temperature tolerance processes, could prove useful in applied strawberry breeding. This study was conducted to identify genotypes of diploid strawberry that differ in their tolerance to low-temperature stress and to investigate whether a set of candidate proteins and metabolites correlate with the level of tolerance. 17 Fragaria vesca, 2 F. nilgerrensis, 2 F. nubicola, and 1 F. pentaphylla genotypes were evaluated for low-temperature tolerance. Estimates of temperatures where 50 % of the plants survived (LT₅₀) ranged from ?4.7 to ?12.0 °C between the genotypes. Among the F. vesca genotypes, the LT₅₀ varied from ?7.7 °C to ?12.0 °C. Among the most tolerant were three F. vesca ssp. bracteata genotypes (FDP821, NCGR424, and NCGR502), while a F. vesca ssp. californica genotype (FDP817) was the least tolerant (LT₅₀ ?7.7 °C). Alcohol dehydrogenase (ADH), total dehydrin expression, and content of central metabolism constituents were assayed in select plants acclimated at 2 °C. The LT₅₀ estimates and the expression of ADH and total dehydrins were highly correlated (r _adh = ?0.87, r _dehyd = ?0.82). Compounds related to the citric acid cycle were quantified in the leaves during acclimation. While several sugars and acids were significantly correlated to the LT₅₀ estimates early in the acclimation period, only galactinol proved to be a good LT₅₀ predictor after 28 days of acclimation (r _galact = 0.79). It is concluded that ADH, dehydrins, and galactinol show great potential to serve as biomarkers for cold tolerance in diploid strawberry.     

Heat tolerance of early developmental stages of glacier foreland species in the growth chamber and in the field

In glacier forelands, seeds readily germinate, however, a high proportion of seedlings die shortly after their appearance. We hypothesized that besides drought, frost and missing safe sites, heat on the ground surface could be one of the major threats for seedlings. The heat strain in different ground strata was assessed from 2007 to 2010. The heat tolerance (LT₅₀) of eleven alpine species from different successional stages was tested considering imbibed (G1) and germinated seeds (G2) as well as seedlings (G3). Additionally, the heat hardening capacity of seedlings was determined in the field. Across all species, LT₅₀ decreased significantly by 9 K from G1 (55 °C) to G3 (46 °C), similarly in all species of the successional stages. Field-grown seedlings had mostly an increased LT₅₀ (2K). Intraspecifically, LT₅₀ of seedlings varied between 40.6 and 52.5 °C. Along the chronosequence, LT₅₀ in G1 was similar, but was higher in G2 and G3 of early successional species. The highest temperatures occurred at 0–0.5 cm in air (mean/absolute maximum: 42.6/54.1 °C) posing a significant heat injury risk for seedlings when under water shortage transpirational cooling is prevented. Below small stones (0–0.5 cm), maxima were 4 K lower, indicating heat safer microsites. Maxima >30 °C occurred at 32.3, >40 °C at 6.2 %. Interannually, 2010 was the hottest year with heat exceeding LT₅₀ at all microsites (0–0.5 cm). Temperature maxima on sandy surfaces were lower than on microsites with gravel (diameter <5–10 mm). The hot summer of 2010 may be a small foretaste of in future more severe and frequent heat waves. Ground surface temperature maxima at the pioneer stage are already now critical for heat survival and may partly explain the high seedling mortality recognized on recently deglaciated terrain.     

Susceptibility of the cigarette beetle Lasioderma serricorne (Coleoptera: Anobiidae) to hypoxia

The susceptibility of the cigarette beetle Lasioderma serricorne (F.) to hypoxia was examined at three different oxygen concentrations (0.5?C0.8, 1.0?C1.3, and 2.0?C2.3?%) and four different temperature/humidity (RH) conditions: 30?°C/75?% RH, 25?°C/75?% RH, 20?°C/43?% RH, and 15?°C/43?% RH. The influence of humidity on mortality was also examined at three humidity levels (21, 43, and 75?% RH) at 1.0?C1.3?% oxygen (O₂) and 25?°C. Our results revealed that adult beetles were the most tolerant at 2.0?C2.3?% O₂ and that the larvae were the most tolerant at O₂ levels <1.0?C1.3?%. Mortality increased with increasing temperatures and decreasing O₂ concentrations. At 30?°C, 75?% RH, and 0.5?C0.8?% O₂, the 99?% lethality (LT₉₉) of larvae was 6.9?days; however, it increased to 20?days when the temperature was decreased to 25?°C or when O₂ levels were increased to 1.0?C1.3?%. Humidity also influenced mortality of both larval and adult beetles. LT₉₉ values for larvae at 25?°C and 1.0?C1.3?% O₂ were 24.0, 44.6, and 50.2?days at 21, 43, and 75?% RH, respectively. Results of this study indicate that a controlled atmosphere (CA) with reduced oxygen levels (<0.5?C0.8?% O₂) represents an effective measure for disinfesting stored tobacco as an alternative to conventional phosphine fumigation at temperatures >30?°C.     

The sea urchin Lytechinus variegatus lives close to the upper thermal limit for early development in a tropical lagoon

Thermal tolerance shapes organisms' physiological performance and limits their biogeographic ranges. Tropical terrestrial organisms are thought to live very near their upper thermal tolerance limits, and such small thermal safety factors put them at risk from global warming. However, little is known about the thermal tolerances of tropical marine invertebrates, how they vary across different life stages, and how these limits relate to environmental conditions. We tested the tolerance to acute heat stress of five life stages of the tropical sea urchin Lytechinus variegatus collected in the Bahía Almirante, Bocas del Toro, Panama. We also investigated the impact of chronic heat stress on larval development. Fertilization, cleavage, morula development, and 4‐armed larvae tolerated 2‐h exposures to elevated temperatures between 28–32°C. Average critical temperatures (LT₅₀) were lower for initiation of cleavage (33.5°C) and development to morula (32.5°C) than they were for fertilization (34.4°C) or for 4‐armed larvae (34.1°C). LT₅₀ was even higher (34.8°C) for adults exposed to similar acute thermal stress, suggesting that thermal limits measured for adults may not be directly applied to the whole life history. During chronic exposure, larvae had significantly lower survival and reduced growth when reared at temperatures above 30.5°C and did not survive chronic exposures at or above 32.3°C. Environmental monitoring at and near our collection site shows that L. variegatus may already experience temperatures at which larval growth and survival are reduced during the warmest months of the year. A published local climate model further suggests that such damaging warm temperatures will be reached throughout the Bahía Almirante by 2084. Our results highlight that tropical marine invertebrates likely have small thermal safety factors during some stages in their life cycles, and that shallow‐water populations are at particular risk of near future warming.     

Photosynthesis in cold acclimated leaves of plants with various degrees of freezing tolerance

The objective of this study was to compare the photosynthetic changes during cold acclimation in various plant types able to acquire different degrees of freezing tolerance. Four herbaceous and six woody plants were hardened under natural or artificial conditions and – after determination of their frost resistance (LT₅₀) – the net photosynthetic rate at an ambient CO₂ of 33 Pa (P_n33), the dependencies of P_n to light and to CO₂ and the room temperature chlorophyll a fluorescence were recorded under optimal conditions. Herbaceous plants acquired freezing tolerances to temperatures between ?10 and ?15°C when hardened at temperatures around 0°C. Most leaves fully developed prior to frost hardening exhibited typical symptoms of senescence after frost hardening. In non-senescing leaves P_n33 was reduced by 15 to 50% mainly due to a reduced stomatal conductance. After hardening at temperatures around ?10°C Brassica survived down to ?24°C, but P_n33 was almost abolished as a result of disturbances in the chloroplasts. After transferring the plants to 20/15°C P_n33 recovered completely within a few days. Woody plants hardened at temperatures around 0°C tolerated – 15 to ?36°C: P_n33 was reduced by 25 to 60% and hardly recovered at 20/15°C. Hardening at ?10°C induced a tolerance of ?32 to n33 was almost totally blocked, but at 20/15°C it returned to the values of the plants hardened at 0°C within a few days. In woody plants disturbances were invariably localized in the chloroplasts. Thus, conifers, and especially Pinus cembra, can survive much lower temperatures than herbaceous plants and, at the same level of freezing tolerance, exhibit appreciably less restriction in relative P_n33.     

Performance of the Striped Mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae) under Variable Conditions of Temperature and Mating

Mealybugs have strong associations with their host plants due to their limitations for dispersal. Thus, environmental conditions and host quality may impact the biological traits of mealybugs. To the best of our knowledge, we are the first to report on the biology of a Brazilian population of the striped mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae), which has recently been reported to infest cotton in Brazil. We evaluated the development and reproductive performance of F. virgata reared under different temperatures (25, 27, and 28°C) and mating status. The type of reproduction was also studied with insects reared on a factitious host and on cotton plants. Shorter development was obtained at 28°C as follows: nymphs generating males and females exhibited three and four instars with a mean duration of 19.1 and 20.5 days, respectively. The nymphal viability ranged from 77 to 96%, and was highest at 25°C. Females reared at 28°C initiated reproduction earlier (16.4 days), but the reproductive period was similar in all temperatures (～16.2 days). Females produced more nymphs at 27 and 28°C (440 and 292 neonates) than at 25°C (277 neonates), although they lived longer at 25°C (63 days). Ferrisia virgata females exhibited only sexual reproduction. Thus, only mated females produced offspring, whereas unmated females died without reproducing. Therefore, the studied population of F. virgata exhibited only sexual reproduction with high survival and offspring production when fed cotton. Furthermore, pumpkin is a feasible host for mass rearing this mealybug species in the laboratory, an opening avenue for future studies.