Adult Fecundity Research Articles

The direct and indirect effects of copper on vector-borne disease dynamics

Metal pollution is a growing concern that affects the health of humans and animals globally. Copper is an essential insect micronutrient required for respiration, pigmentation and oxidative stress protection but can also act as a potentially toxic trace element. While several studies have focused on the negative fitness effects of copper on the aquatic larvae of mosquitoes, the effects of larval copper exposure on adult mosquito fitness (i.e., survival and fecundity) and their ability to transmit parasites (i.e., vector competence) remains unclear. Here, using a well-studied model vector-parasite system, the mosquito Aedes aegypti and parasite Dirofilaria immitis, we show that sublethal copper exposure in larval mosquitoes alters adult female fecundity and vector competence. Specifically, mosquitoes exposed to copper had a hormetic fecundity response and mosquitoes exposed to 600μg/L of copper had significantly fewer infective parasite larvae than control mosquitoes not exposed to copper. Thus, exposure of mosquito larvae to copper levels far below EPA-mandated safe drinking water limits (1300μg/L) can impact vector-borne disease dynamics not only by reducing mosquito abundance (through increased larval mortality), but also by reducing parasite transmission risk. Our results also demonstrated that larval copper is retained through metamorphosis to adulthood in mosquitoes, indicating that these insects could transfer copper from aquatic to terrestrial foodwebs, especially in urban areas where they are abundant. To our knowledge this is the first study to directly link metal exposure with vector competence (i.e., ability to transmit parasites) in any vector-parasite system. Additionally, it also demonstrates unequivocally that mosquitoes can transfer contaminants from aquatic to terrestrial ecosystems. These results have broad implications for public health because they directly linking contaminants and vector-borne disease dynamics, as well as linking mosquitoes and contaminant dynamics.

Methoxyfenozide, a Molting Hormone Agonist, Affects Autogeny Capacity, Oviposition, Fecundity, and Fertility in Culex pipiens (Diptera: Culicidae).

The current study aimed to evaluate the effects of methoxyfenozide (RH-2485), an insect growth disrupter (IGD) belonging to molting hormone agonist class, against female adults of Culex pipiens L. under laboratory conditions. Lethal concentrations (LC50 = 24.54 µg/liter and LC90 = 70.79 µg/liter), previously determined against fourth instar larvae, were tested for adult female fertility, fecundity and oviposition after tarsal contact before mating and any bloodmeal. Methoxyfenozide was found to alter negatively their autogeny capacity and oviposition. A strong reduction of 56% and 72% (P < 0.001) in females' autogeny capacity was observed in both treated series, respectively. Alteration in oviposition were found to be higher with LC90 (OAI-LC90 = -0.62) than with the LC50 (OAI-LC50 = -0.42). Also fecundity and hatching rate (fertility) were significantly reduced in treated series as compared to controls. A significant reduction of 37.65 and 28.23% in fecundity and decrease of 56.85 and 71.87% in fertility were found, respectively in LC50 and LC90 treated series. Obtained data clearly demonstrated that methoxyfenozide have significant depressive effect on reproductive potential against medically important vector with minimizing ecotoxicological risks in mosquitoes management.

Bioassay Essential Oils on Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae)

Background: Tribolium confusum and Tribolium castaneum are pests spread inside the stores and homes. These pests infest stored grains and many others seeds in the stores and bakery. These controlled by insecticides. The essential have a promising research results in controlling these pests and decreasing the insect infestations. The natural essential oils have a low effect on the human, non-target insects, and do not pollute the environments. This research is an alternative approach to natural control these two stored product pests. Methods: Four essential oils namely, Lantana camara, Acorus calamus, caraway oil and Ammi majus were estimated on two stored product insects T. confusum and T. castaneum. Encapsulation method by the technology of polymerization was followed. The nano oils at 0.5% were estimated on the 3rd larval instars. Percentages of accumulative mortality were calculated after seven days of the experiments. The effect of nano-oils on oviposition experiments made by spraying two grams of foams of the tested oils and their nano formulations mixed with 100 gram of wheat. Results data obtained detected that, the Percentage of larval mortality increase by increasing the concetrations for both insects T. confusum and T. castaneum. T. confusum tested larvae were more susceptible to the treatments than T. castaneum larvae. Nano A. majus oil showed a stronger effecte than that L. camara or A. calamus oil. Adult emergence percent and fecundity showed a highly decreasing after treatments with nano-oil L. camara, A. calamus, A. majus oils under storage conditions, compared to those of the controls or non-nano-oils. The results suggested that nano A. majus can be used as a valuable tool in pest management programs of T. confusum and T. castaneum Conclusion: The results of this work indicate that some essential oils might be helpful management of pests in the stores because of their fumigant and odor action. Essential oils of plant origin contain active ingredients which are effective against many insects. Nano formulations of essential oils, through controlled release, prevent speed violate and decay and, also increase the stability of the oils. Treated foam, using L. camara, A. majus, caraway, and A. calamus oils gave protectthe wheat seeds from two pests infestations.

Influence of Temperature on the Life-Cycle Dynamics of Aedes albopictus Population Established at Temperate Latitudes: A Laboratory Experiment

Simple SummaryMosquitoes represent a potential major public health concern, as they are capable of transmitting several pathogens when biting humans. It is well known that temperature is a crucial factor affecting mosquito biology: for instance, warmer conditions can increase survival and fecundity. Here, we quantify the influence of different temperatures on the bionomics of Aedes albopictus, which is a mosquito species native to Southeast Asia that has been able to spread worldwide during the last forty years. We used specimens collected from northern Italy to assess if temperate individuals are characterized, possibly thanks to an adaptation process, by a different thermal response with respect to subtropical individuals. We found that immature stages are well adapted to colder temperatures, which nonetheless seem to prevent any blood-feeding activity. Adult longevity and fecundity were substantially greater at mild conditions. This thermal adaptation might increase the length of the breeding season and could allow the colonization of areas at higher altitude, resulting in an overall increased risk for potential transmission of Ae. albopictus-borne pathogens.The mosquito species Aedes albopictus has successfully colonized many areas at temperate latitudes, representing a major public health concern. As mosquito bionomics is critically affected by temperature, we experimentally investigated the influence of different constant rearing temperatures (10, 15, 25, and 30 °C) on the survival rates, fecundity, and developmental times of different life stages of Ae. albopictus using a laboratory colony established from specimens collected in northern Italy. We compared our results with previously published data obtained with subtropical populations. We found that temperate Ae. albopictus immature stages are better adapted to colder temperatures: temperate larvae were able to develop even at 10 °C and at 15 °C, larval survivorship was comparable to the one observed at warmer conditions. Nonetheless, at these lower temperatures, we did not observe any blood-feeding activity. Adult longevity and fecundity were substantially greater at 25 °C with respect to the other tested temperatures. Our findings highlight the ability of Ae. albopictus to quickly adapt to colder environments and provide new important insights on the bionomics of this species at temperate latitudes.

Effects of Low Temperature Exposure on Diapause, Development, and Reproductive Fitness of the Emerald Ash Borer (Coleoptera: Buprestidae): Implications for Voltinism and Laboratory Rearing.

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), native to Northeast Asia, is the most destructive invasive ash (Fraxinus spp.) pest in the United States. In the present study, we evaluated the effect of exposure of diapausing mature fourth instars (J-shaped larvae, JL) of EAB to cool temperatures, either 1.7 or 12.8°C for 1-9 mo, on their post-chill development including adult emergence, longevity, and lifetime fecundity under standard rearing conditions (26 ± 0.5°C, 16:8 h L:D). In addition, we determined the effect of different stages of the larvae chilled at 12.8°C for 3 mo on the subsequent post-chill development to EAB adults. Findings from the study revealed that a period (≥2 mo) of chill at 12.8°C is required for the termination of the EAB diapause. However, chill treatment of the larvae at the near zero temperature (1.7°C) does not result in the post-diapause larval development to adults, regardless of the chill time (1-9 mo). In addition, our results showed that chill treatment of immature young larvae (L1-L4 prior to JL) results in little production of EAB adults, indicating that EAB diapause predominantly as JL. Findings of this study may be useful to laboratory rearing of EAB from eggs through continuous generations and help us understand the pest's voltinism resulting from the diapause and post-diapause development under different climatic conditions.

Aphicidal activity of Bacillus thuringiensis strain AH‐2 against cotton aphid (Aphis gossypii)

AbstractBacillus thuringiensis (Bt) is the most commercialized entomopathogenic species. However, the low efficacy against notorious sap‐sucking Hemipteran pests and the high costs of production, reduce the applicability of Bt biopesticides. In this context, B. thuringiensis AH‐2 (Bt‐2) isolated from soil was found to release parasporal inclusions and aphicidal activity. Bt‐2 showed optimal growth at pH 8 and 30°C in tryptic soy broth (TSB) and maintained normal growth when cultured in cost‐effective test media, pink brown (PB), supplemented with either glucose (PBG) or sucrose (PBS). To study aphicidal activity against cotton aphid (Aphis gossypii), Bt‐2 and a commercial B. thuringiensis subspecies kurstaki (Btk) were used. Using third nymph (3 N) instars, treatment with Bt‐2 caused 70.2, 78.1 and 88.4% mortality at 10, 25 and 50% culture concentrations, respectively. Similarly, Btk resulted in 79.9, 80.4 and 92.9% mortality at 10, 25 and 50%, respectively. When cultured in TSB, PBG and PBS media, Bt‐2 culture (50%) resulted in 85.9, 82.9 and 82.2% 3 N mortality, respectively. Equally, Btk caused a mortality of 79.9, 78.9 and 78.9% in TSB, PBG and PBS, respectively. Bt‐2 exerted a notably higher aphicidal efficacy at 24 h after treatment compared to Btk, especially at low concentration. Moreover, both Bt strains significantly suppressed adult fecundity compared to control. At 50% culture concentration, Bt‐2 and Btk suppressed adult fecundity by 98.3 and 91.1%, respectively. Our result demonstrates a strong aphicidal efficacy of Bt‐2, and its potential production using cost‐effective PB medium.

From individual vital rates to population dynamics: An integral projection model for European native oysters in a marine protected area

Abstract Following an 85% decline in global oyster populations, there has been a recent resurgence in interest in the restoration of the European native oyster Ostrea edulis. Motivations for restoration from environmental stakeholders most often include recovering lost habitats and associated biodiversity and supporting ecosystem function. In coastal communities, another important justification is recovery of traditional and low‐impact fisheries but this has received less attention. Many restoration projects across Europe focus on the translocation of adult stocks, under the assumption that the limit to population growth and recovery is adult growth and survival. This may not necessarily be the case, especially where knowledge of large extant adult populations exists as in the Blackwater, Crouch, Roach and Colne Marine Conservation Zone in Essex, UK. Identifying what limits population growth for restoration and recovery is an important conservation tool. Here, the first size‐dependent survival, growth and fecundity data for free‐living O. edulis from a novel field experiment are used to parameterize an Integral Projection Model that examines the sensitivity of a flat oyster population to variation in individual vital rates and to potential harvesting – an original objective of a coastal community‐led restoration project. Given the high adult fecundity in this species, population recovery is most sensitive to changes in recruitment success; however, elasticity (proportional sensitivity of the population) is more evenly spread across other parameters when recruitment is already high. Based on locally agreed management objectives, recovery to double the current stock biomass should take 16–66 years (mean = 30 years) without active intervention. At that point, harvest rates could be sustained below 5% of the harvestable adult size whilst ensuring λs remains above 1.

Involvement of apolipoprotein D in desiccation tolerance and adult fecundity of Acyrthosiphon pisum

Apolipoprotein D (ApoD) is a lipocalin superfamily member that plays important roles in the transport of small hydrophobic molecules, lipid metabolism, and stress resistance. Cuticular hydrocarbons are the principal components of the epicuticular lipid layer and play a critical role in water retention against environmental desiccation stress; however, the mechanism underlying the role of ApoD in insect desiccation tolerance has not yet been elucidated. Here, we report the molecular constitution, functional analysis, and phylogenetic relationship of the ApoD gene in Acyrthosiphon pisum (ApApoD). We found that ApApoD was transcribed throughout the life cycle of A. pisum, but was prominently expressed in the embryonic period and abdominal cuticle. In addition, we optimized the dose and silencing duration of RNAi, observing that RNAi against ApApoD significantly reduced the levels of both internal and cuticular hydrocarbons and adult fecundity. Moreover, cuticular hydrocarbon deficiency increased the sensitivity of aphids to desiccation stress and reduced their survival time, while desiccation stress significantly increased ApApoD expression. Together, it is confirmed that ApApoD participates in regulating cuticular hydrocarbon content of aphids under desiccation stress and is crucial for aphid reproduction. Therefore, the ApApoD gene of A. pisum may be a potential target for RNAi-based insect pest control due to its involvement in cuticular hydrocarbon accumulation and reproduction.

Encapsulation of sea fennel (Crithmum maritimum) essential oil in nanoemulsion and SiO2 nanoparticles for treatment of the crop pest Spodoptera litura and the dengue vector Aedes aegypti

Crithmum maritimum L. (Apiaceae), also known as sea fennel, is a halophythe plant colonizing cliffs and coastal dunes and pebble of the Mediterranean sea and Atlantic ocean. Based on previous reports, this herb produces an essential oil endowed with insecticidal effects against various pests and insect vectors. In the present work, we investigated the insecticidal effectiveness of the seed essential oil and its encapsulated forms (nanoemulsion and SiO2 nanoparticles, SiNPs) against larvae of the mosquito Aedes aegypti and cotton leafworm Spodoptera litura, in terms of larval contact toxicity and reduction of adult longevity and fecundity. The essential oil composition was characterized by the phenylpropanoids dillapiole and myristicin and oxygenated monoterpenes γ-terpinene and thymol methyl ether. Based on the insecticidal assays, we noticed that all developed products, namely sea fennel essential oil, nanoemulsion and encapsulated silica nanoparticles, showed significant toxicity against larvae and pupae of Ae. aegypti and S. litura. Notably, the SiNPs showed LC50 values ranging from 8.823 (I instar) to 17.911 μL/L (pupa) on Ae. aegypti (I instar-pupa) and from 24.610 (I instar) to 64.546 μL/L (pupa) on S. litura. Furthermore, all three selected bioinsecticides reduced longevity and fecundity in both targets. Overall the sea fennel essential oil and its encapsulated forms, i.e. nanoemulsion and SiNPs, are promising alternatives for the control of insects causing human diseases and damages in agriculture.

Changes in prey, turbidity, and competition reduce somatic growth and cause the collapse of a fish population

AbstractSomatic growth exerts strong control on patterns in the abundance of animal populations via effects on maturation, fecundity, and survival rates of juveniles and adults. In this paper, we quantify abiotic and biotic drivers of rainbow trout growth in the Colorado River, Arizona, USA, and the resulting impact on spatial and temporal variation in abundance. Inferences are based on ~10,000 observations of individual growth rates obtained through an intensive mark–recapture effort conducted over 5 yrs (2012–2016) in a 130‐km long study segment downstream of Glen Canyon Dam. Prey availability, turbidity‐driven feeding efficiency, and intraspecific competition were the dominant drivers of rainbow trout growth. Discharge, water temperature, and solar insulation were also evaluated but had a smaller influence. Mixed‐effect models explained 79–82% of the variability in observed growth rates, with fixed covariate effects explaining 79–87% of the total variation in growth parameters across five reaches and 18 quarterly sampling intervals. Reductions in growth owing in part to a phosphorous‐driven decline in prey availability, led to a substantive loss in mass and poor fish condition. This in turn lowered survival rates and delayed maturation, which led to a rapid decline in abundance and later recruitments. Reductions in feeding efficiency, due to episodic inputs of fine sediment from tributaries, and warmer water temperatures, contributed to reduced growth in downstream reaches, which led to more severe declines in abundance. Somatic growth rates increased following the population collapse due to reduced competition, and in the absence of substantive increases in prey availability. Our study elucidates important linkages between abiotic and biotic factors, somatic growth, and vital rates, and demonstrates how variation in somatic growth influences temporal and spatial patterns in abundance.

Spatial and environmental effects on Coho Salmon life history trait variation.

Adult size, egg size, fecundity, and mass of gonads are affected by trade‐offs between reproductive investment and environmental conditions shaping the evolution of life history traits among populations for widely distributed species. Coho salmon Oncorhynchus kisutch have a large geographic distribution, and different environmental conditions are experienced by populations throughout their range. We examined the effect of environmental variables on female size, egg size, fecundity, and reproductive investment of populations of Coho Salmon from across British Columbia using an information theoretic approach. Female size increased with latitude and decreased with migration distance from the ocean to spawning locations. Egg size was lowest for intermediate intragravel temperature during incubation, decreased with migration distance, but increased in rivers below lakes. Fecundity increased with latitude, warmer temperature during the spawning period, and river size, but decreased in rivers below lakes compared with rivers with tributary sources. Relative gonad size increased with latitude and decreased with migration distance. Latitude of spawning grounds, migratory distance, and temperatures experienced by a population, but also hydrologic features—river size and headwater source—are influential in shaping patterns of reproductive investment, particularly egg size. Although, relative gonad size varied with latitude and migration distance, how gonadal mass was partitioned gives insight into the trade‐off between egg size and fecundity. The lack of an effect of latitude on egg size suggests that local optima for egg size related to intragravel temperature may drive the variation in fecundity observed among years.

Impact of a candidate vaccine on the dynamics of salmon lice (Lepeophtheirus salmonis) infestation and immune response in Atlantic salmon (Salmo salar L.).

Infection with parasitic copepod salmon louse Lepeophtheirus salmonis, represents one of the most important limitations to sustainable Atlantic salmon (Salmo salar L.) farming today in the North Atlantic region. The parasite exerts negative impact on health, growth and welfare of farmed fish as well as impact on wild salmonid populations. It is therefore central to ensure continuous low level of salmon lice with the least possible handling of the salmon and drug use. To address this, vaccination is a cost-effective and environmentally friendly control approach. In this study, efficacy of a vaccine candidate, containing a peptide derived from ribosomal protein P0, was validated post infestation with L. salmonis, at the lab-scale. The sampling results showed good potential of the vaccine candidate when administered intraperitoneally in the host, in reducing the ectoparasite load, through reduction of adult female lice counts and fecundity and with greater presumptive effect in F1 lice generation. The sampling results correlated well with the differential modulation of pro-inflammatory, Th1, Th2 and T regulatory mediators at the transcript level at different lice stages. Overall, the results supports approximately 56% efficacy when administered by intraperitoneal injection. However, additional validation is necessary under large-scale laboratory trial for further application under field conditions.

Lethal and sub-lethal effects of low-temperature exposures on Halyomorpha halys (Hemiptera: Pentatomidae) adults before and after overwintering

Cold winter temperatures can influence insects’ survival in temperate zones. Brown marmorated stink bug, Halyomorpha halys (Stål) overwinters as adults in natural and human-made structures. In this study, we characterized low temperature mortality rates of H. halys adults that were either entering (ENA) or exiting (EXA) overwintering microhabitats. We considered the effect of different duration of cold exposure on mortality. We determined the impact of insect nutritional status and weight on cold tolerance. We additionally evaluated the effects of cold exposure on H. halys adult longevity and fecundity. Mortality of ENA and EXA adults was determined for 6 h and 2 h periods at − 2.5 °C and 2.5 °C respectively. EXA adults displayed higher mortality rates compared to ENA individuals at the low-temperature regimes. Halyomorpha halys adult survival rate was higher when their nutrient index (EXA individuals only) and weight were high. Low-temperature exposure increased longevity, but reduced fecundity of ENA females. The data further highlight how extreme spring frost events can result in significantly increased mortality levels of H. halys adults.

Sublethal and transgenerational effects of lambda-cyhalothrin on the mirid bugs Lygus pratensis Linnaeus and Polymerus cognatus Fieber

The plant mirid bugs, Lygus pratensis Linnaeus and Polymerus cognatus Fieber, are key pests on economically important cotton crops and ecologically important grassland in northwestern China. Lambda-cyhalothrin is frequently used against mirid bugs in the regions. In this study, we examined the sublethal and transgenerational effects of short-term exposure to lambda-cyhalothrin on biological traits using a miminal dose, LD5 [0.484 ng/L. pratensis adult, and 0.171 ng/P. cognatus adult], a low lethal dose, LD25 [1.353 ng/L. pratensis adult, and 0.781 ng/P. cognatus adult] and a moderate lethal dose, LD50 [2.766 ng/L. pratensis adult, and 2.243 ng/P. cognatus adult]. Direct exposure to LD50 of lambda-cyhalothrin led to decreased adult longevity, shorter female oviposition period and lower fecundity of the parental generation for both species, whereas treatment with LD5 lambda-cyhalothrin stimulated female fecundity on L. pratensis, but not on P. cognatus. The F1 generation underwent transgenerational effects, i.e. there was delayed egg-laying period and larval development and decreased hatchability for both species, decreased adult longevity and fecundity for L. pratensis, and shortened adult longevity for the LD50 group of P. cognatus. Compared with the untreated control group, the net reproductive rate (R0), the intrinsic rate of increase (rm), and finite rate of increase (λ) were significantly decreased for the groups treated with different doses of lambda-cyhalothrin, whereas the generation time (T) was increased. Our results demonstrate that sublethal effects of lambda-cyhalothrin can retard development and suppress population growth for both of these mirid species. Therefore, this insecticide can be used effectively against mirid bugs in northern China and its application strategy to control mirid bug is discussed.

Methanolic Extract of Winter Cherry Causes Morpho-Histological and Immunological Ailments in Mulberry Pyralid Glyphodes pyloalis.

The effect of Withania somnifera a medicinal plant seed extract was tested against lesser mulberry pyralid, a potential pest of mulberry. The mulberry leaves were used for silk production in rural areas of northern Iran. The extract was administered orally by leaf dipping method in two lower (5%W/V) and higher (15%W/V) dosages to third instar larvae (<24 h) for biological assays and to fifth instar larvae (<24 h) for Physiological studies. The results showed formation of larvoids (Ls), larval-pupal intermediates (LPIs), pupoids (Ps) and pupal-adult intermediates (PAIs). The results showed increased larval duration by 1.7 and 2 folds in 5 and 15% treatment, respectively. Fecundity of resultant adults was decreased by 1.2 and 1.3 in 5 and 15% treatment, respectively. Except approximate digestibility (AD) and consumption index (CI) all other feeding indices showed reduction. The feeding deterrence was prominent at 15% (87%) and 5% showing 48% deterrence. Our enzymatic and non-enzymatic assessments upon treatment showed reduction in key components, except detoxifying enzymes. However, the activity of an important enzyme involved in cuticle hardening and immunity called phenoloxidase was reduced. We also investigated the histology of midgut for further analysis and found drastic changes in main cellular elements. Immunological changes following treatment was noticeable in reduced Total Hemocyte Count but surprisingly increased Differential Hemocyte Count. However, the hemocytes structure was extremely damaged. The reduced number of eggs in treated but survived adults indicated reduced ovaries, with vacuolization both in trophocytes and oocytes. The key chemical compounds showed reductions particularly at 15%. The present results are concomitant with few earlier studies on this medicinal plant and deserve further studies particularly in deriving key chemicals that alter metamorphosis similar to insect growth regulators.

Exogenous Gibberellin GA3 Enhances Defense Responses in Rice to the Brown Planthopper Nilaparvata lugens (Stål)

Applying chemical elicitors is considered a promising approach for controlling pests in the field. Our previous studies have shown that gibberellin (GA) signaling positively regulates the resistance of rice (Oryza sativa) to the brown planthopper (BPH) Nilaparvata lugens (Stal). Yet, whether the exogenous application of GAs can enhance the resistance of rice to BPH remains unknown. Here, we investigated the influence of exogenous GA3 on both defense responses in rice and BPH performance. We found that pretreating rice with GA3 decreased transcript levels of a mitogen-activated protein kinase (MAPK) and three WRKY transcription factors, as well as levels of BPH-elicited jasmonic acid (JA) and three phenolic acids but increased the release of ethylene. Moreover, GA3 treatment negatively affected the survival and development of BPH nymphs as well as the fecundity of BPH female adults. These findings suggest that GA3 promotes the resistance of rice to BPH and may, thus, be used to improve pest management in rice.

Feeding of carob (Ceratonia siliqua) to sheep infected with gastrointestinal nematodes reduces faecal egg counts and worm fecundity

The present study explored the anthelmintic effects of condensed tannins (CT) in carob (Ceratonia siliqua) pods fed to sheep against gastrointestinal nematodes. Three independent in vivo trials tested whether i) carob pod (CaBP)-containing feed had an anthelmintic effect and if yes, which was the optimal concentration in the diet; ii) whether this effect could be attributed to tannins through the polyethylene glycol (PEG) test and iii) whether there were any synergistic effects when combined with another tannin-containing feed (e.g. sainfoin). In all trials 6-month old nematode-naive lambs, experimentally infected with both Haemonchus contortus and Trichostrongylus colubriformis, were used. Faecal egg counts (FEC) were performed regularly and at the end of each trial adult worm counts (AWC) and female worm fecundity were recorded. In trial 1, 35 lambs (five groups of seven lambs) were fed different CaBP concentrations ranging from 0% to 12 % w/w. FEC declined up to 39.2 % only in the group fed with 12 %CaBP, while a declining trend (P < 0.06) was demonstrated for the AWC of T. colubriformis, which was associated with the increasing concentration of CaBP in feed. Female worm fecundity was reduced in groups fed CaBP for both parasites, however this was only significant for H. contortus (P < 0.001), in a dose dependent manner. In trial 2, four groups of six infected lambs each were used, which received the carob diets CaBP or CaBP + PEG, and the tannin-free diets with or without PEG (C or C + PEG). Results showed that FEC of Groups C, C + PEG, and CaBP + PEG were comparable throughout the trial, while the group receiving only CaBP showed lower FEC from DAY 25 onwards. AWC showed a reduction (67.7 %) only for H. contortus (P < 0.03). Reversal of the anthelmintic effect of CaBP after PEG administration suggested that CT contributed to the anthelmintic action. However, no effect of CaBP was observed on T. colubriformis AWC and on female worm fecundity for both species. Finally, for trial 3 four groups of six lambs each received a diet based on CaBP, sainfoin (S) or a combination (CaBP + S) and were compared to a control (C) diet of lucerne. On DAY 37 FEC values in groups CaBP + S and S tended to be lower compared to the two other groups (C, CaBP), while for AWCs no significant differences were observed for both parasites. The fecundity of H. contortus and T. colubriformis demonstrated significant differences between the treated and control groups, with lower values in the animals receiving CaBP + S. Overall, the results supported the hypothesis that carob had an anthelmintic effect due to its CT, but there was no clear indication of a synergistic effect with sainfoin.

Lipophorin receptor regulates the cuticular hydrocarbon accumulation and adult fecundity of the pea aphid Acyrthosiphon pisum.

Cuticular hydrocarbons form a barrier that protects terrestrial insects from water loss via the epicuticle. Lipophorin loads and transports lipids, including hydrocarbons, from one tissue to another. In some insects, the lipophorin receptor (LpR), which binds to lipophorin and accepts its lipid cargo, is essential for female fecundity because it mediates the incorporation of lipophorin by developing oocytes. However, it is unclear whether LpR is involved in the accumulation of cuticular hydrocarbons and its precise role in aphid reproduction remains unknown. We herein present the results of our molecular characterization, phylogenetic analysis, and functional annotation of the pea aphid (Acyrthosiphon pisum) LpR gene (ApLpR). This gene was transcribed throughout the A. pisum life cycle, but especially during the embryonic stage and in the abdominal cuticle. Furthermore, we optimized the RHA interference (RNAi) parameters by determining the ideal dose and duration for gene silencing in the pea aphid. We observed that the RNAi-based ApLpR suppression significantly decreased the internal and cuticular hydrocarbon contents as well as adult fecundity. Additionally, a deficiency in cuticular hydrocarbons increased the susceptibility of aphids to desiccation stress, with decreased survival rates under simulated drought conditions. Moreover, ApLpR expression levels significantly increased in response to the desiccation treatment. These results confirm that ApLpR is involved in transporting hydrocarbons and protecting aphids from desiccation stress. Furthermore, this gene is vital for aphid reproduction. Therefore, the ApLpR gene of A. pisum may be a novel RNAi target relevant for insect pest management.

Expression patterns and functional analysis of the short neuropeptide F and NPF receptor genes in Rhopalosiphum padi.

The short neuropeptide F (sNPF) and NPF receptor (NPFR) genes play important roles in many physiological processes. However, information on the survival-related functions of sNPF and NPFR under different stress conditions is lacking in aphids. In this study, we cloned sNPF and NPFR, and investigated the expression levels of these genes in different developmental stages, wing morphs, and stress conditions of the bird cherry-oat aphid (Rhopalosiphum padi L.), an important agricultural pest. The sNPF and NPFR transcript levels varied among developmental stages, and their expression levels in alate females were significantly higher than those in apterous females. In addition, starvation resulted in significantly increased sNPF expression, which then recovered after refeeding. Heat stress and insecticides significantly affected transcription of both genes. sNPF and NPFR knockdown in R. padi using RNA interference revealed optimal interference efficiency at 48 h post-injection. sNPF knockdown significantly decreased adult longevity, 15-d fecundity, and food intake. Additionally, mortality under starvation, insecticides, and heat stress conditions was significantly higher after injection with double-stranded sNPF in R. padi. NPFR knockdown significantly affected food intake and starvation resistance in R. padi. These results strongly indicate that sNPF plays vital roles in food intake, longevity, and reproduction in R. padi, and it can significantly affect the pest's response to stress conditions.

Reduced Mythimna separata infestation on Bt corn could benefit aphids.

Use of genetically engineered plants that express insecticidal Cry proteins derived from Bacillus thuringiensis (Bt) have been proven efficacious for managing lepidopteran pests. However, in some cases herbivores that are not targeted by the Bt trait have increased in importance. It has been suggested that reduced caterpillar damage to Bt crops could lead to decreased levels of induced plant defensive compounds which might benefit other non-target herbivores. Here we investigated the potential effect of reduced damage by larvae of Mythimna separata on aphid populations in Bt corn. We compared the performance of Rhopalosiphum maidis feeding on non-Bt corn plants that had been infested by M. separata larvae or were uninfested. The results showed that caterpillar-infested corn plants significantly reduced the fitness of R. maidis leading to a prolonged nymphal development time, reduced adult longevity and fecundity compared to uninfested plants. Consequently, the population growth rate of corn aphids feeding on caterpillar-infested corn plants was significantly lower than on uninfested plants. As expected, the aphids performed significantly better on Lepidoptera-resistant Bt corn than on non-Bt corn when plants were infested with M. separata, since the caterpillars caused very little damage to the Bt plants. The current findings indicate that reduced M. separata infestation could benefit aphid development in Bt corn. Bt corn has the potential to be commercialized in China in the near future and aphids and other non-target pests should be monitored in the farming fields.