Pre-adult Duration Research Articles

Effect of elevated CO2 on interactions between the host plant Phaseolus vulgaris and the invasive western flower thrips, Frankliniella occidentalis

Elevated CO2 can alter the growth and development of herbivorous insects by changing the host plants, including nutrient quality and defensive chemicals/metabolites. The western flower thrips, Frankliniella occidentalis, is a highly destructive invasive pest in agriculture worldwide. In this study, we investigated the effect of elevated CO2 on the growth, development and reproduction of F. occidentalis by changing its host plant of kidney bean Phaseolus vulgaris and, in particular, the hormonal regulation of the transcription factors in F. occidentalis. Elevated CO2 increased the contents of total amino acids, soluble sugar and soluble protein in P. vulgaris. Besides, elevated CO2 shortened the pre-adult duration (PAD) and longevity of F. occidentalis, lowered their survival rate and increased the weight and fecundity. PAD was positively correlated with the expression levels of br, Krh-1, JHEH and EIP in F. occidentalis larvae. The longevity of F. occidentalis female adults was negatively correlated with JHEH, but positively correlated with ER and EIP. The fecundity of F. occidentalis female adults was negatively correlated with ER and Vg, but positively correlated with JHEH. We have demonstrated that elevated CO2 could enhance the nutrient quality of host plants and, therefore, accelerate the development and reproduction of F. occidentalis, which is regulated by JH, MH and Vg.

Sublethal and transgenerational effects of dinotefuran on biological parameters and behavioural traits of the mirid bug Apolygus lucorum

The mirid bug, Apolygus lucorum, has become a major pest of many crops and fruit trees since the widespread adoption of Bt cotton in northern China. Neonicotinoid insecticides, such as dinotefuran, applied to control this pest may show sublethal effects, but evidence for such effects is lacking. Here, we investigated the sublethal and transgenerational effects of dinotefuran on biological parameters and feeding behavioural traits of A. lucorum using the age-stage, two-sex life table and electrical penetration graphs (EPGs), respectively. The LC10 and LC30 of dinotefuran against 3rd-instar nymphs of A. lucorum were 14.72 and 62.95 mg L−1, respectively. These two concentrations significantly extended the development duration from 3rd-instar nymph to adult in parent generation (F0). LC30 also increased the oviposition period and male adult longevity and reduced nymphal survival rate in the F0. For offspring generation (F1), the egg duration, preadult duration, and total preoviposition period were significantly lower at LC10 than in the control, and the egg duration, duration of 4th-instar nymphs, preadult duration, oviposition period, and fecundity were also decreased at LC30. However, the four demographic parameters of F1 generation, namely, net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T), were not affected by dinotefuran. The significant differences in the number of probes and duration of each of four feeding waveforms failed to be detected when A. lucorum nymphs treated by dinotefuran feed on Bt cotton plants without insecticide exposure. Overall, the dinotefuran concentrations tested here have sublethal, but no transgenerational impacts on A. lucorum.

Toxicity and sublethal effects of two plant allelochemicals on the demographical traits of cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae).

Plant allelochemicals are a group of secondary metabolites produced by plants to defend against herbivore. The mortality of two plant allelochemicals (tannic acid and gossypol) on the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), were investigated using feeding assays and the sublethal effects were evaluated using the age-stage, two-sex life table approach. Tannic acid and gossypol have deleterious effects on A. gossypii, and as the concentrations increased, the mortality of cotton aphid increased. The life history traits of A. gossypii including the developmental duration of each nymph stage, the longevity, oviposition days, total preadult survival rate and adult pre-oviposition period were not significantly affected by sublethal concentration of tannic acid (20 mg/L) and gossypol (50 mg/L), while the population parameters (r, λ and R0) were significantly affected by these two plant allelochemicals. Furthermore, tannic acid can increase the pre-adult duration time and TPOP but reduce the fecundity of A. gossypii significantly compared to the control and gossypol treatment groups. These results are helpful for comprehensively understanding the effects of plant allelochemicals on A. gossypii.

Downregulation of imidacloprid resistant genes alters the biological parameters in Colorado potato beetle, Leptinotarsa decemlineata Say (chrysomelidae: Coleoptera)

Colorado potato beetle, Leptinotarsa decemlineata Say (coleoptera: chrysomelidae), is the important pest of potato all over the world. This insect pest is resistant to more than 50 active compounds belonging to various chemical groups. Potential of RNA interference (RNAi) was explored to knock down transcript levels of imidacloprid resistant genes in Colorado potato beetle (CPB) under laboratory conditions. Three important genes belonging to cuticular protein (CP), cytochrome P450 monoxygenases (P450) and glutathione synthetase (GSS) families encoding imidacloprid resistance were targeted. Feeding bio-assays were conducted on various stages of imidacloprid resistant CPB lab population by applying HT115 expressing dsRNA on potato leaflets. Survival rate of insects exposed to CP-dsRNA decreased to 4.23%, 15.32% and 47.35% in 2nd, 3rd and 4th instar larvae respectively. Larval weight and pre-adult duration were also affected due to dsRNAs feeding. Synergism of RNAi with imidacloprid conducted on the 2nd instar larvae, exhibited 100% mortality of larvae when subjected to reduced doses of GSS and CP dsRNAs along with imidacloprid. Utilization of three different dsRNAs against imidacloprid resistant CPB population reveal that dsRNAs targeting CP, P450 and GSS enzymes could be useful tool in management of imidacloprid resistant CPB populations.

Sub-lethal concentrations of the entomopathogenic fungus, Beauveria bassiana increase fitness costs of Helicoverpa armigera (Lepidoptera: Noctuidae) offspring.

We assessed the effects of exposure of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae to the entomopathogenic fungus Beauveria bassiana (isolate DC2) on life history parameters of the subsequent generation. Mortality assays against second instar larvae showed B. bassiana isolates to be significantly virulent, causing high mortality. Life history parameters such as developmental time, fecundity and survivorship were affected in the offspring of survivors of exposure to LC25 and LC50 concentrations of B. bassiana DC2. Pre-adult duration of H. armigera was significantly extended and total longevity and female progeny fecundity were decreased. Oviposition duration was shortened compared to offspring of untreated controls. All population parameters including intrinsic (r) and finite (λ) rates of increase and net (R0) and gross (GRR) reproductive rates were significantly decreased in offspring derived from H. armigera larvae treated with B. bassiana DC2. The intrinsic rate of increase (r) was 0.198 d-1, 0.120 d-1 and 0.111 d-1, respectively, for the F1 generation of controls (untreated), LC25- and LC50-treated cotton bollworm. The morphogenetic effects of B. bassiana observed due to the indirect effect of sub-lethal concentrations included abnormal pupae and adults and mortality resulted from the malformations. Pupal weight was reduced in offspring of treated individuals but sex ratios did not differ. Our results revealed that B. bassiana increased fitness costs of H. armigera in both direct (mortality) and indirect (disruption of normal development) ways. Adverse effects of sub-lethal fungal treatments on the parent generation carried over to the next generation.

Quantitative Analysis of Long-Term Mass Rearing of Neoseiulus californicus (Acari: Phytoseiidae) on Almond Pollen.

Long-term feeding effects of the almond pollen on the life table parameters of Neoseiulus californicus McGregor were assessed after 5, 10, and 20 generations after introduction in the rearing arena. Furthermore, to evaluate behavioral characteristics of the mass-reared predator (strain A) in face with the real prey, functional and numerical responses of the predator to different densities of the twospotted spider mite nymphs were determined, and the obtained data were compared with those reared on twospotted spider mite (strain T). Long-term rearing did not significantly affect total fecundity of N. californicus (ranged from 37.79 to 41.91 eggs). Nevertheless, preadult duration in the 5th generation was significantly longer than the 10th and 20th generations. The intrinsic rate of increase (r) in the 10th (0.2056 d-1) and 20th (0.2201 d-1) generations had not significant difference together. However, the r value slightly dropped in the 5th generation (0.1706 d-1) because of the irregular offering of fresh pollen to the rearing colonies before that. Both strains of N. californicus exhibited a type II functional response; however, the N. californicus reared on the almond pollen (strain A) had a higher attack rate (a) and shorter handling time (Th). The individuals reared on the almond pollen had a greater size than those reared on twospotted spider mite; its higher predation potential is probably due to this characteristic. Consequently, the rearing of N. californicus on the almond pollen positively affected its attributes including high survivorship, body size, and fecundity, and subsequently higher potential to control twospotted spider mite.

Ecological impact of a secondary bacterial symbiont on the clones of Sitobion avenae (Fabricius) (Hemiptera: Aphididae)

Many insects harbor heritable endosymbionts, whether obligatory or facultative, and the role of facultative endosymbionts in shaping the phenotype of these species has become increasingly important. However, little is known about whether micro-injected endosymbionts can have any effects on aphid clones, which was measured using various ecological parameters. We examined the effects between symbiotic treatments and the vital life history traits generated by Regiella insecticola on the life table parameters of Sitobion avenae. The results showed that R. insecticola can decrease the intrinsic rate of increase (r), the finite rate of increase (λ) and birth rate and can increase the mean generation times (T) of S. avenae clones, suggesting that R. insecticola may decelerate the normal development of the hosts. No significant differences of these parameters were observed between the examined Sitobion avenae clones, and the symbiont treatment by genotype interaction affected only the net reproduction rate R0, pre-adult duration and total longevity but not the other parameters. Additionally, a population projection showed that R. insecticola decelerated the growth of the S. avenae clones. The evocable effects of R. insecticola on the S. avenae clones may have significant ramifications for the control of S. avenae populations under field/natural conditions.

Linking pollen quality and performance of Neoseiulus californicus (Acari: Phytoseiidae) in two-spotted spider mite management programmes.

It has been shown that pollen as a dietary supplement may increase the establishment of generalist predatory mites, and therefore pest control by these mites can be provided. Life table studies were performed to evaluate the nutritional value of seven different pollens (almond, castor-bean, date-palm, maize, bitter-orange, sunflower and mixed bee pollen) as a supplementary food source for the spider mite predator Neoseiulus californicus McGregor. In addition, the nutritional quality of each pollen species was assessed through morphological and chemical analysis. Preadult duration was longer when the predator fed on castor-bean pollen (10.01 days) and bee pollen (9.94 days) compared with the others (5.58-7.27 days). The cohort reared on almond pollen had the highest intrinsic rate of increase (r) (0.231 day-1 ), and those on mixed bee pollen had the lowest r (0.005 day-1 ). The levels of nutritional content (sugar, lipid and protein) were significantly different among tested pollens. Comparison of N. californicus life table parameters on different diets revealed that the almond pollen (and after that the maize pollen) was a more suitable diet than the others. These findings will be useful in developing appropriate strategies for conservation of N. californicus to control spider mites. © 2016 Society of Chemical Industry.

Life-history traits of Drosophila melanogaster populations exhibiting early and late eclosion chronotypes.

BackgroundThe hypothesis that circadian clocks confer adaptive advantage to organisms has been proposed based on its ubiquity across almost all levels of complexity and organization of life-forms. This thought has received considerable attention, and studies employing diverse strategies have attempted to investigate it. However, only a handful of them have examined how selection for circadian clock controlled rhythmic behaviors influences life-history traits which are known to influence Darwinian fitness. The ‘early’ and ‘late’ chronotypes are amongst the most widely studied circadian phenotypes; however, life-history traits associated with these chronotypes, and their consequences on Darwinian fitness remain largely unexplored, primarily due to the lack of a suitable model system. Here we studied several life-history traits of Drosophila melanogaster populations that were subjected to laboratory selection for morning (early) and evening (late) emergence.ResultsWe report that the late eclosion chronotypes evolved longer pre-adult duration as compared to the early eclosion chronotypes both under light/dark (LD) and constant dark (DD) conditions, and these differences appear to be mediated by both clock dependent and independent mechanisms. Furthermore, longer pre-adult duration in the late chronotypes does not lead to higher body-mass at pupariation or eclosion, but the late females were significantly more fecund and lived significantly shorter as compared to the early females.ConclusionsCoevolution of multiple life-history traits in response to selection on timing of eclosion highlights correlations of the genetic architecture governing timing of eclosion with that of fitness components which suggests that timing ecologically relevant behaviors at specific time of the day might confer adaptive advantage.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0622-3) contains supplementary material, which is available to authorized users.

Development of Bradysia odoriphaga (Diptera: Sciaridae) as affected by humidity: an age–stage, two-sex, life-table study

The gnat Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae) is an important pest of Chinese chive (Allium tuberosum Rottler ex Sprengel). Although B. odoriphaga outbreaks are thought to depend on soil humidity, the mechanism by which humidity affects the outbreaks is poorly understood. In this study, the life history of B. odoriphaga (Diptera: Sciaridae) on Chinese chive was studied with an age–stage, two-sex life table and with relative humidity (RH) at 50, 60, 70, or 80 %. The developmental time of eggs and larvae, total preoviposition duration, and total preadult duration were longer at 50 % RH than at higher RH values. The mean total preadult duration was 34.16 days at 50 % RH and ranged from 27.34 to 31.81 days at 60–80 % RH. The mean fecundity was significantly higher at 70 % RH (as high as 62.88 eggs/female) than at 50, 60, or 80 % RH (from 33.41 to 50.52 eggs/female). The intrinsic capacity of increase (r), net production rate (R 0), and finite rate of increase (λ) increased as RH increased from 50 to 80 %, and mean generation time (T) showed the opposite trend. This study provides insight into the phenology of B. odoriphaga and shows that high RH promotes outbreaks of B. odoriphaga.

Population statistics and biological traits of Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae) affected by LC30 of thiamethoxam and pirimicarb

Although selective pesticides are recommended to use in integrated pest management (IPM) programmes, they could adversely affect biological agents. So, the aim of the current study was to investigate the LC30 of pirimicarb and thiamethoxam on Hippodamia variegata. Two pesticides, pirimicarb and thiamethoxam, when applied at concentrations of 1522.8 and 251.3 mg (ai)/L, respectively, on the third instar larvae of the insect, produced 30% mortality. Also, results showed that neither pirimicarb nor thiamethoxam affect stage age distribution (cx), fecundity (eggs/female) and adult development time. These two pesticides extended preadult duration significantly (p < 0.0001, F = 31.22, df = 122). Also, survival rate (lx) and age-specific reproductive value (vx) decreased and some changes in age-specific life expectancy (ex) happened. Generally, more adverse effects were found in the population treated by thiamethoxam. The results showed that pirimicarb and thiamethoxam have potential to harm the predatory ladybird in IPM programme, though in sublethal doses.

Environmentally-induced modulations of developmental rates do not affect the selection-mediated changes in pre-adult development time of fruit flies Drosophila melanogaster

In a previous study we had shown that 55 generations of selection for faster egg-to-adult development in fruit flies Drosophila melanogaster results in shortening of pre-adult duration by ∼29-h (∼12.5%) and speeding-up of circadian clock period (τ) by ∼0.5-h, implying a positive correlation between development time and τ(. In Drosophila, change in ambient temperature is known to alter the rate of pre-adult development but not the speed of circadian clocks whereas 12:12-h warm/cold (WC) cycles are likely to alter both pre-adult development rate and τ( (via entrainment). To study the effect of overall speeding-up/slowing-down of pre-adult development and circadian clocks on the selection-mediated difference in pre-adult development time, we subjected developing flies to the following conditions: (i) different ambient temperatures (18, 25 and 29°C) under constant darkness (DD) to alter the rate of pre-adult development, or (ii) cyclic WC conditions (WC1–-25:18 or WC2–-29:25°C) to alter rate of development and τ(. The results revealed that the selected (FD) stocks develop faster than controls (BD) by ∼52, 28 and 21-h, at 18, 25 and 29°C, respectively, and by 28 and 26-h under WC1 and WC2, respectively. The τ( of activity/rest rhythm decreased considerably at 18°C but it did not differ between the FD and BD flies, which suggests a break-down of correlation between development time and τ(, seen under their normal rearing conditions (constant darkness - – DD at 25°C). While the absolute difference in development time between FD and BD stocks increased or decreased under cooler or warmer conditions, the relative difference in their pre-adult development time remained largely unaltered. These results suggest that manipulations in ambient conditions independently changes development time and τ(, resulting in a break-down of the genetic correlation between them.