Development response of Spodoptera exigua to eight constant temperatures: Linear and nonlinear modeling

Temperature-dependent development of Spodoptera exigua (Hübner) were evaluated at eight constant temperatures of 12, 15, 20, 25, 30, 33, 34 and 36 °C with a variation of 0.5 °C on sugar beet leaves. No development occurred at 12 °C and 36 °C. Total developmental time varied from 120.50 days at 15 °C to 14.50 days at 33 °C. As temperature increased from 15 °C to 33 °C, developmental rate (1/developmental time) of S. exigua increased but declined at 34 °C. The lower temperature threshold (T_min) was estimated to be 12.98 °C and 12.45 °C, and the thermal constant (K) was 294.99 DD and 311.76 DD, using the traditional and Ikemoto–Takai linear models, respectively. The slopes of the Ikemoto–Takai linear model for different immature stages were different, violating the assumption of rate isomorphy. Data were fitted to three nonlinear models to predict the developmental rate and estimate the critical temperatures. The T_min values estimated by Lactin-2 (12.90 °C) and SSI (13.35 °C) were higher than the value estimated by Briere-2 (8.67 °C). The estimated fastest development temperatures (T_fast) by the Briere-2, Lactin-2 and SSI models for overall immature stages development of S. exigua were 33.4 °C, 33.9 °C and 32.4 °C, respectively. The intrinsic optimum temperature (T_Φ) estimated from the SSI model was 28.5 °C, in which the probability of enzyme being in its native state is maximal. The upper temperature threshold (T_max) values estimated by these three nonlinear models varied from 34.00 °C to 34.69 °C. These findings on thermal requirements can be used to predict the occurrence, number of generations and population dynamics of S. exigua.     

Temperature-dependent development of Lista haraldusalis (Walker) (Lepidoptera: Pyralidae) on Platycarya strobilacea

The effect of constant temperatures on development and survival of Lista haraldusalis (Walker) (Lepidoptera: Pyralidae), a newly reported insect species used to produce insect tea in Guizhou province (China), was studied in laboratory conditions at seven temperatures (19 °C, 22 °C, 25 °C, 28 °C, 31 °C, 34 °C, and 37 °C) on Platycarya strobilacea. Increasing the temperature from 19 °C to 31 °C led to a significant decrease in the developmental time from egg to adult emergence, and then the total developmental time increased at 34 °C. Egg incubation was the stage where L. haraldusalis experienced the highest mortality at all temperatures. The survival of L. haraldusalis was significantly higher at 25 °C and 28 °C, whereas none of the eggs hatched at 37 °C. Common and Ikemoto linear models were used to describe the relationship between the temperature and the developmental rate for each immature stage of L. haraldusalis. The estimated values of the lower temperature threshold and thermal constant of the total immature stages using Common and Ikemoto linear models were 11.34 °C and 11.20 °C, and 939.85 and 950.41 degree-days, respectively. Seven nonlinear models were used to fit the experimental data to estimate the developmental rate of L. haraldusalis. Based on the biological significance for model evaluation, Ikemoto linear, Logan-6, and SSI were the best models that fitted each immature stage of L. haraldusalis and they were used to estimate the temperature thresholds. These thermal requirements and temperature thresholds are crucial for facilitating the development of factory-based mass rearing of L. haraldusalis.     

Developmental temperature responses of Chrysoperla agilis (Neuroptera: Chrysopidae), a member of the European carnea cryptic species group

Chrysoperla agilis Henry et al. is one of the five cryptic species of the carnea group found in Europe. Identification of these species is mainly based on the distinct mating signals produced by both females and males prior to copulation, although there are also morphological traits that can be used to distinguish among different cryptic species. Ecological and physiological cryptic species-specific differences may affect their potential as important biological agents in certain agroecosystems. To understand the effects of temperature on the life-history traits of C. agilis preimaginal development, adult longevity and reproduction were studied at seven temperatures. Temperature affected the development, survival and reproduction of C. agilis. Developmental time ranged from approximately 62 days at 15 °C to 15 days at 30 °C. Survival percentages ranged from 42% at 15 °C to 76% at 27 °C. One linear and five nonlinear models (Briere I, II, Logan 6, Lactin and Taylor) used to model preimaginal development were tested to describe the relationship between temperature and developmental rate. Logan 6 model fitted the data of egg to adult development best according to the criteria adopted for the model evaluation. The predicted lower developmental threshold temperatures were 11.4 °C and 11.8 °C (linear model), whereas the predicted upper threshold temperatures (Logan 6 model) were 36.6 and 36.9 °C for females and males, respectively. Adult life span, preoviposition period and lifetime cumulative oviposition were significantly affected by temperature. The effect of rearing temperature on the demographic parameters is well summarized with the estimated values of the intrinsic rate of increase (r_m) which ranged from 0.0269 at 15 °C to 0.0890 at 32 °C and the highest value recorded at 27 °C (0.1530). These results could be useful in mass rearing C. agilis and predicting its population dynamics in the field.     

Estimation of developmental parameters for adult emergence of Gonatocerus morgani,a novel egg parasitoid of the glassy-winged sharpshooter,and development of a degree-day model

The effects of temperature on the development (egg–adult emergence) of Gonatocerus morgani Triapitsyn, a newly-described parasitoid of Homalodisca vitripennis (Germar), were determined at 14.8, 18.7, 23.5, 26.9, 28.7, 30.4, 32.8, and 33.8 °C in the laboratory. Survival rate (percent adult emergence from parasitized host eggs) varied significantly among the experimental temperatures, with the highest (59%) and lowest (0%) occurring at 30.4 and 33.8 °C, respectively. The survival rates (%) were fitted with a polynomial model to describe a temperature-dependent pattern. Developmental rates (1/d) across seven temperatures were fitted with the nonlinear Briere model, which estimated the lower threshold to be 8.06 °C, the optimal temperature to be 29.22 °C, and the upper threshold to be 33.49 °C. A linear model fitted to developmental rates at 14.8–28.7 °C indicated that 189.75 degree-days above the lower threshold of 9.71 °C were required to complete development. A simulation model of G. morgani adult emergence was constructed to predict daily counts over the entire range of constant temperatures by incorporating the survival rate model, the Briere model, and the Weibull model. In outdoor validation, a degree-day model for predicting adult emergence showed ?2 d differences between prediction and observation. Based on the observed temperature requirement, the insect could complete thirteen to sixteen generations per year in southern California, depending on weather and location.     

Temperature-dependent development of overwintering Sericinus montela Gray (Lepidoptera: Papilionidae) pupae and its validation

The developmental time and survival of overwintering Sericinus montela Gray pupae were studied at four constant temperatures (15.0, 20.0, 25.0, and 30.0 °C), 40 ± 10% relative humidity, and 10:14 h light:dark cycle. The developmental time of both sexes decreased with increasing temperature between 15.0 °C (70.18 days for females and 55.28 days for males) and 30.0 °C (19.60 days for females and 13.78 days for males). The development periods of females were longer than those of males at each constant temperature. The relationship between the developmental rate and temperature was fitted by a linear model and a nonlinear developmental rate model (Lactin 1). The mortality of overwintered S. montela pupae was lowest at 25.0 °C (16.7%) and highest at 15.0 °C (36.7%). The lower developmental thresholds were 12.38 and 12.16 °C for females and males, respectively. The distribution of development completion for females and males was described by the two-parameter Weibull distribution equation (r² = 0.87 for females and r² = 0.94 for males). The date for the cumulative 50% adult emergence was within one or two days of that predicted using the Lactin 1 model. The temperature-dependent developmental model for S. montela could be applied to predict the timing of spring emergence in different geographical locations and will be helpful in developing a full-cycle phenology model for S. montela.     

Impact of fluctuating temperatures on development of the koinobiont endoparasitoid Venturia canescens

The effect of temperature on the biology of Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae) is well understood under constant temperature conditions, but less so under more natural, fluctuating conditions. Herein we studied the influence of fluctuating temperatures on biological parameters of V. canescens. Parasitized fifth-instar larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were reared individually in incubators at six fluctuating temperature regimes (15–19.5 °C with a mean of 17.6 °C, 17.5–22.5 °C with a mean of 19.8 °C, 20–30 °C with a mean of 22.7 °C, 22.5–27.5 °C with a mean of 25 °C, 25.5-32.5 °C with a mean of 28.3 °C and 28.5–33 °C with a mean of 30 °C) until emergence and death of V. canescens adults. Developmental time from parasitism to adult eclosion, adult longevity and survival were recorded at each fluctuating temperature regime. In principle, developmental time decreased with an increase of the mean temperature of the fluctuating temperature regime. Upper and lower threshold temperatures for total development were estimated at 34.9 and 6.7 °C, respectively. Optimum temperature for development and thermal constant were 28.6 °C and 526.3 degree days, respectively. Adult longevity was also affected by fluctuating temperature, as it was significantly reduced at the highest mean temperature (7.0 days at 30 °C) compared to the lowest one (29.4 days at 17.6 °C). Survival was low at all tested fluctuating temperatures, apart from mean fluctuating temperature of 25 °C (37%). Understanding the thermal biology of V. canescens under more natural conditions is of critical importance in applied contexts. Thus, predictions of biological responses to fluctuating temperatures may be used in population forecasting models which potentially influence decision-making in IPM programs.     

Use of life table statistics and degree day values to predict the colonisation success of Hydrellia lagarosiphon Deeming (Diptera: Ephydridae), a leaf mining fly of Lagarosiphon major (Ridley) Moss (Hydrocharitaceae), in Ireland and the rest of Europe

Hydrellia lagarosiphon is a leaf mining fly of the submerged aquatic plant Lagarosiphon major and native to South Africa. With many favorable attributes this fly has the potential to be a valuable biological control agent of L. major, which has become a problematic weed in many parts of the world. Reproductive and developmental biology of H. lagarosiphon was determined at four constant temperatures (10, 13.5, 16.5, 20 °C) to evaluate the rate of increase and predicted colonisation success in areas where L. major occurs and areas where its continued spread is probable. Development rates increased with decreasing temperatures and were greatest at 10 °C taking 157.9 days. Linear regression of developmental rate data for temperatures 10–20 °C indicated that 517 degree days were required above a minimum of 7.5 °C to complete development. Between two and eight generations per year were estimated across the climatic regions of Europe using the degree day model. The fitted quadratic model for the net reproductive rate (R_o) indicated that R_o falls below 1.0 at 9.9 °C, suggesting a decline in population growth when fly populations are subjected to prolonged periods of temperatures below 10 °C. The values of R_o for selected sites range from 0 to 13, with all but a few sites in northern Europe being suitable for the establishment of H. lagarosiphon. A minimum of two generations were required each year to sustain population growth and most biogeographical regions in Europe appeared suitable for the establishment of permanent populations of H. lagarosiphon. The implications for the release strategy of the fly are discussed.     

Heat accumulation and development rate of massed maggots of the sheep blowfly,Lucilia cuprina (Diptera: Calliphoridae)

Blowfly larvae aggregate on exposed carcasses and corpses and pass through three instars before wandering from the carcass and pupating. The developmental landmarks in this process can be used by forensic entomologists to estimate the time since the insects colonised the carcass, which sets a minimum post mortem interval. Large aggregations of feeding larvae generate a microclimate with temperatures up to 15 °C above ambient conditions, which may accelerate larval development and affect forensic estimates of post-mortem intervals. This study investigated the effects of heat accumulated by maggot masses of Lucilia cuprina at aggregations of 20, 50 and 100 larvae, each at incubation temperatures of 18 °C, 24 °C and 30 °C, using body length and life stage as developmental indicators. Aggregation temperatures reached up to 18.7 °C above ambient temperature, with significant effects of both size and temperature of the aggregation on the development time of its larvae. Survivorship was highest for all life stages at 24 °C, which is near the developmental optimum of L. cuprina. The results of this study provide a broadly applicable method of quantifying heat accumulation by aggregations of a wide range of species of forensic importance, and the results obtained from such studies will demonstrate that ambient temperature cannot be considered the only source of heat that blowfly larvae experience when they develop on a carcass. Neglect of temperatures within larval aggregations will result in an overestimation of post-mortem intervals and thus have far-reaching medicolegal consequences.     

Effect of variable dew temperatures on infection of green foxtail by Pyricularia setariae,Drechslera gigantea,and Exserohilum rostratum

A thermogradient apparatus was used to investigate the effect of variable dew temperatures on infection of green foxtail by the indigenous pathogen Pyricularia setariae (Ps) and the exotic pathogens Drechslera gigantea (Dg), and Exserohilum rostratum (Er) from the southern USA that showed bioherbicide potential against several grassy weeds. This device is capable of creating multiple diurnal temperature cycles, mimicking daily temperature fluctuations that occur under field conditions. Seven temperature regimes, i.e., 15/10 °C, 20/5 °C, 20/15 °C, 25/10 °C, 25/20 °C, 30/15 °C, and 30/25 °C (maximum/minimum), were used with temperature cycling from maximum to minimum and then back up to maximum in a 24 h period. Ps and Dg were much more virulent than Er on green foxtail, resulting in higher levels of disease and weed control. Dg was little affected by the dew temperatures in terms of plant infection and was more efficacious than Ps under cooler dew temperatures (15/10 °C and 20/5 °C), causing twice as much disease. This greater amount of disease coincided with higher conidial germination, appressorial formation and infection-hypha frequency by Dg at the lower temperatures. The efficacy of Ps improved as dew temperature increased, accompanied by a higher percentage of germination and more frequent appressorial production. Dg caused severe disease 2 d after inoculation whereas Ps required 4 d to initiate disease symptoms. These observations suggest that Dg is a superior candidate than Ps for green foxtail control on the Canadian prairies.     

Effects of different temperatures on the life history of Evania appendigaster L. (Hymenoptera: Evaniidae), a solitary oothecal parasitoid of Periplaneta americana L. (Dictyoptera: Blattidae)

The influence of temperatures on the life parameters of the solitary oothecal parasitoid Evania appendigaster, was investigated in the laboratory. Parasitized oothecae of Periplaneta americana were left to develop under seven constant temperatures: 15, 17, 20, 25, 30, 35, and 40 °C. At the end, we found that: (i) E. appendigaster was able to complete development within the temperature range of 17–34 °C; (ii) mean adult longevity decreased as temperature increased, with the temperature of 40 °C being fatal in a matter of hours; (iii) males lived longer than females between 15 and 30 °C; (iv) adult emergence rate was the highest at 25 °C, and (v) no wasps emerged at 15 or 40 °C. Non-emerged oothecae contained either unhatched eggs or dead larvae. We determined the theoretical lower developmental threshold and thermal constant for the complete development as 12.9 °C and 584.8 day-degrees for males, and 13.1 °C and 588.2 day-degrees for females, respectively. A good balance between faster development, maximum adult longevity and good egg viability was obtained between 25–30 °C, and that would be the best temperature range for rearing E. appendigaster.     

Temperature-dependent development of Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) and their validation in semi-field condition

The developmental time and survival of the immature stages of Cnaphalocrocis medinalis Guenée were studied at nine constant temperatures (15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, and 35 °C), 40 ± 10% relative humidity, and a 16:8 h light:dark cycle. The total developmental time decreased with increasing temperature between 15 (115.6 days) and 32.5 °C (20.9 days), but increased above 32.5 °C. The relationship between the developmental rate and temperature was fitted by a linear model and three nonlinear developmental rate models (Logan 6, Briere 1, and Shi et al.). The nonlinear shape of temperature-dependent development was best described by the Briere 1 model (r² = 0.99), and this was supported by statistical information criteria. The total mortality of immature C. medinalis was lowest at 25 °C (67.2%) and highest at 35 °C (98.1%). The distribution of the developmental times of each stage was described by the two-parameter Weibull distribution equation (r² = 0.84–0.96). The predicted date for the cumulative 50% moth emergence was within a variation of one day using the Briere 1 model. The temperature-dependent developmental models for C. medinalis could be applied to determine an optimal management strategy for C. medinalis in paddy fields, and will be helpful in developing a full-cycle phenology model for C. medinalis.     

Incubation temperature affects hatching success,embryonic expenditure of energy and hatchling phenotypes of a prolonged egg-retaining snake,Deinagkistrodon acutus (Viperidae)

We used eggs of Deinagkistrodon acutus to study the effects of incubation temperature on hatching success, embryonic expenditure of energy and hatchling phenotypes. One egg from each of the 15 fertile clutches was dissected for determination of egg composition, and a total of 164 eggs were incubated at five constant temperatures. Embryonic mortality increased dramatically at 30 °C, and none of eggs incubated at 32 °C hatched. Within the range from 24 to 30 °C, temperature affected incubation length and most hatchling traits examined. The mean incubation length at 24, 26, 28 and 30 °C was 36.4, 28.7, 21.8 and 15.7 days, respectively. Embryos developing at higher temperatures (28 and 30 °C) consumed more energy but produced less developed (and hence smaller) hatchlings, which characteristically had larger residual yolks but smaller carcasses. A principal component analysis resolved two components (with eigenvalues ⩾1) from ten size (initial egg mass)-free hatchling variables, accounting for 79.3% of variation in the original data. The first component (43.8% variance explained) had high positive loading for size-free values of dry mass, lipid mass, energy contents and ash mass of hatchlings, and the second component (35.5% variance explained) had high positive loading for size-free values of SVL, carcass dry mass and fatbody dry mass. Hatchlings from different incubation temperatures did not differ in scores on the first axis of the principal component analysis, whereas hatchlings from higher incubation temperatures (28 and 30 °C) had significantly lower scores on the second axis than did those from lower incubation temperatures (24 and 26 °C). As the second axis mainly represents traits relating to the developmental condition at hatching, the analysis therefore provided further evidence that eggs incubated at higher temperatures produced less developed hatchlings. Taken together, our data show that the optimal temperatures for embryonic development are relatively low in D. acutus largely due to its use of relatively cool habitats.     

Parameter estimation for a temperature-dependent development model of Thrips palmi Karny (Thysanoptera: Thripidae)

Development of immature Thrips palmi Karny was investigated at 12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, and 35 °C, 20–40% RH and a photoperiod of 14:10 (L:D) h. Developmental time decreased with increasing temperature up to 32.5 °C in all stages. The total developmental time was longest at 12.5 °C (64.2 days) and shortest at 32.5 °C (9.2 days). The lower developmental threshold was 10.6, 10.6, 9.1, and 10.7 °C for egg, larva, prepupa, and pupa, respectively. The thermal constant required to complete the respective stage was 71.7, 59.2, 18.1, and 36.8DD. The lower threshold temperature and thermal constant were 10.6 °C and 183.3DD, respectively, for total immature development. The nonlinear relationship between developmental rate and temperature was well described by the modified Sharpe and DeMichele biophysical model (r² = 0.905–0.998). The distribution of developmental completion of each stage was described by the 3-parameter Weibull function (r² = 0.855–0.927). The temperature-dependent developmental models of T. palmi developed in this study could be used to predict its seasonal phenology in field and greenhouse vegetable crops.     

Effects of constant temperature,exposure period,and age on diapause induction in Trichogramma dendrolimi

Trichogramma dendrolimi can be successfully reproduced in fresh eggs dissected from ovaries of the Chinese tussah silkworm (Antheraea pernyi) and is widely used in biological control of lepidopteran agricultural and forest pests in China. Diapause induction of T. dendrolimi in A. pernyi eggs was investigated through exposing the parasitoid to six constant temperatures (16, 13, 10, 7, 4, and 1 °C) for 19 exposure periods between 10 and 46 days. The sensitive age of T. dendrolimi for diapause induction was explored through a separate experiment to examine the parasitoids that had developed for 2, 3, 4, 5, 6, 7, and 8 days at 26 °C after parasitization, under the six constant temperatures, respectively. Diapause was induced at 10 or 7 °C, and the induction period was 4–6 weeks. The sensitive age of T. dendrolimi to react at the induction temperature was 2–3 days (at 26 °C). At 7 and 10 °C, the diapause rate increased with increasing exposure period and decreased with increased T. dendrolimi age at exposure. The optimum method to induce diapause in T. dendrolimi consisted of exposing hosts for parasitization at 26 °C for 8 h, and then keeping them at 26 °C for 40 h, finally, moving them into 10 °C for 4 weeks.     

The effects of increased constant incubation temperature and cumulative acute heat shock exposures on morphology and survival of Lake Whitefish (Coregonus clupeaformis) embryos

Increasing incubation temperatures, caused by global climate change or thermal effluent from industrial processes, may influence embryonic development of fish. This study investigates the cumulative effects of increased incubation temperature and repeated heat shocks on developing Lake Whitefish (Coregonus clupeaformis) embryos. We studied the effects of three constant incubation temperatures (2 °C, 5 °C or 8 °C water) and weekly, 1-h heat shocks (+3 °C) on hatching time, survival and morphology of embryos, as these endpoints may be particularly susceptible to temperature changes. The constant temperatures represent the predicted magnitude of elevated water temperatures from climate change and industrial thermal plumes. Time to the pre-hatch stage decreased as constant incubation temperature increased (148 d at 2 °C, 92 d at 5 °C, 50 d at 8 °C), but weekly heat shocks did not affect time to hatch. Mean survival rates and embryo morphometrics were compared at specific developmental time-points (blastopore, eyed, fin flutter and pre-hatch) across all treatments. Constant incubation temperatures or +3 °C heat-shock exposures did not significantly alter cumulative survival percentage (~50% cumulative survival to pre-hatch stage). Constant warm incubation temperatures did result in differences in morphology in pre-hatch stage embryos. 8 °C and 5 °C embryos were significantly smaller and had larger yolks than 2 °C embryos, but heat-shocked embryos did not differ from their respective constant temperature treatment groups. Elevated incubation temperatures may adversely alter Lake Whitefish embryo size at hatch, but weekly 1-h heat shocks did not affect size or survival at hatch. These results suggest that intermittent bouts of warm water effluent (e.g., variable industrial emissions) are less likely to negatively affect Lake Whitefish embryonic development than warmer constant incubation temperatures that may occur due to climate change.     

Wheat quality related differential expressions of albumins and globulins revealed by two-dimensional difference gel electrophoresis (2-D DIGE)

Comparative proteomics analysis offers a new approach to identify differential proteins among different wheat genotypes and developmental stages. In this study, the non-prolamin expression profiles during grain development of two common or bread wheat cultivars (Triticum aestivum L.), Jing 411 and Sunstate, with different quality properties were analyzed using two-dimensional difference gel electrophoresis (2-D DIGE). Five grain developmental stages during the post-anthesis period were sampled corresponding to the cumulative averages of daily temperatures (°C: 156 °C, 250 °C, 354 °C, 447 °C and 749.5 °C). More than 400 differential protein spots detected at one or more of the developmental stages of the two cultivars were monitored, among which 230 proteins were identified by MS. Of the identified proteins, more than 85% were enzymes possessing different physiological functions. A total of 36 differential proteins were characterized between the two varieties, which are likely to be related to wheat quality attributes. About one quarter of the proteins identified expressed in multiple spots with different pIs and molecular masses, implying certain post-translational modifications (PTMs) of proteins such as phosphorylations and glycosylations. The results provide new insights into biochemical mechanisms for grain development and quality.     

Effect of temperature and host species on parasitism,development time and sex ratio of the egg parasitoid Trichogrammatoidea lutea Girault (Hymenoptera: Trichogrammatidae)

The developmental biology of Trichogrammatoidea lutea Girault (Hymenoptera: Trichogrammatidae) was studied at six constant temperatures (18, 21, 24, 27, 30 and 35 °C) on eggs of three lepidopteran host species: Helicoverpa armigera (Hübner) (Noctuidae), Chilo partellus (Swinhoe) (Crambidae) and Cadra cautella (Walker) (Pyralidae). T. lutea did not complete development at 35 °C on any of the three host species. Parasitism levels were highest on H. armigera at 27 °C (58%), C. cautella at 27 and 30 °C (31% and 28%) and C. partellus between 24 and 30 °C (13–17%). Realized progeny of T. lutea per parasitized host egg was influenced by host size. The number of progeny of T. lutea per parasitized host egg was highest on H. armigera, followed by C. partellus and lowest on C. cautella. The sex ratio was female biased on C. partellus, female biased on C. cautella with the exception of 21 °C and close to 1:1 on H. armigera. The rate of development from egg to pupa and egg to adult was fastest on H. armigera and slowest on C. partellus. Lower thresholds for development and degree days (DD) of T. lutea from egg to adult were 12.8 °C and 105.4 DD on H. armigera, 11.3 °C and 141.6 DD on C. partellus and 12.9 °C and 118.2 DD on C. cautella, respectively. Based on these results, H. armigera is the most suitable host for mass rearing of T. lutea for biological control of Lepidoptera pests because of the relatively high parasitism levels, short development time, greater clutch size and balanced sex ratio. C. cautella may also be used although longer exposure times might be required due to lower parasitism levels.     

Effect of thermal stress on metabolic and oxidative stress biomarkers of Hoplosternum littorale (Teleostei,Callichthyidae)

The present study aimed to investigate in Hoplosternum littorale (Hancock, 1828) the effects of different water temperatures (10 °C, 25 °C-control group- and 33 °C) on physiologic and metabolic traits following acute (1 day) and chronic (21 days) exposures. We analyzed several biomarker responses in order to achieve a comprehensive survey of fish physiology and metabolism under the effect of this natural stressor. We measured morphological indices, biochemical and hematological parameters as well as oxidative stress markers. To evaluate energy consumption, muscle and hepatic total lipid, protein and glycogen concentrations were also quantified. Extreme temperatures exposures clearly resulted in metabolic adjustments, being liver energy reserves and plasma metabolites the most sensitive parameters detecting those changes. We observed reduced hepatosomatic index after acute and chronic exposure to 33 °C while glycogen levels decreased at both temperatures and time of exposure tested. Additionally, acute and chronic exposures to 10 °C increased liver lipid content and plasma triglycerides. Total protein concentration was higher in liver and lower in plasma after chronic exposures to 10 °C and 33 °C. Acute exposition at both temperatures caused significant changes in antioxidant enzymes tested in the different tissues without oxidative damage to lipids. Antioxidant defenses in fish failed to protect them when they were exposed for 21 days to 10 °C, promoting higher lipid peroxidation in liver, kidney and gills. According to multivariate analysis, oxidative stress and metabolic biomarkers clearly differentiated fish exposed chronically to 10 °C. Taken together, these results demonstrated that cold exposure was more stressful for H. littorale than heat stress. However, this species could cope with variations in temperature, allowing physiological processes and biochemical reactions to proceed efficiently at different temperatures and times of exposure. Our study showed the ability of H. littorale to resist a wide range of environmental temperatures and contributes for the understanding of how this species is adapted to environments with highly variable physicochemical conditions.     

Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi larvae and juveniles

Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi Nikolsky larvae and juveniles was investigated. The fish (start at 12 d post hatch) were reared for nearly 6 months at five constant temperatures of 10, 14, 18, 22 and 26 °C. Then juvenile fish being acclimated at three temperatures of 14, 18 and 22 °C were chosen to determine their critical thermal maximum (CTMax) and lethal thermal maximum (LTMax) by using the dynamic method. Growth rate of S. kozlovi larvae and juveniles was significantly influenced by temperature and fish size, exhibiting an increase with increased rearing temperature, but a decline with increased fish size. A significant ontogenetic variation in the optimal temperatures for maximum growth were estimated to be 24.7 °C and 20.6 °C for larvae and juveniles of S. kozlovi, respectively. The results also demonstrated that acclimation temperature had marked effects on their CTMax and LTMax, which ranged from 32.86 °C to 34.54 °C and from 33.79 °C to 34.80 °C, respectively. It is suggested that rearing temperature must never rise above 32 °C for its successful aquaculture. Significant temperature effects on the growth rate and thermal tolerance both exhibit a plasticity pattern. Determination of critical heat tolerance and optima temperature for maximum growth of S. kozlovi is of ecological significance in the conservation and aquaculture of this species.     

Can acclimation of thermal tolerance,in adults and across generations,act as a buffer against climate change in tropical marine ectotherms?

Thermal acclimation capacity was investigated in adults of three tropical marine invertebrates, the subtidal barnacle Striatobalanus amaryllis, the intertidal gastropod Volegalea cochlidium and the intertidal barnacle Amphibalanus amphitrite. To test the relative importance of transgenerational acclimation, the developmental acclimation capacity of A. amphitrite was investigated in F₁ and F₂ generations reared at a subset of the same incubation temperatures. The increase in CT_max (measured through loss of key behavioural metrics) of F₀ adults across the incubation temperature range 25.4–33.4 °C was low: 0.00 °C (V. cochlidium), 0.05 °C (S. amaryllis) and 0.06 °C (A. amphitrite) per 1 °C increase in incubation temperature (the acclimation response ratio; ARR). Although the effect of generation was not significant, across the incubation temperature range of 29.4–33.4 °C, the increase in CT_max in the F₁ (0.30 °C) and F₂ (0.15 °C) generations of A. amphitrite was greater than in the F₀ (0.10 °C). These correspond to ARR's of 0.03 °C (F₀), 0.08 °C (F₁) and 0.04 °C (F₂), respectively. The variability in CT_max between individuals in each treatment was maintained across generations, despite the high mortality of progeny. Further research is required to investigate the potential for transgenerational acclimation to provide an extra buffer for tropical marine species facing climate warming.