Oviposited Eggs Research Articles

Ultrastructure and Function of the Stalk Gland Complex of Pompholyx faciemlarva (Rotifera: Monogononta).

Many planktonic rotifers carry their oviposited eggs until hatching. In some species, the eggs are attached to the mother via secretions from her style gland, which forms a thread that extends from her cloaca. In species of Pompholyx, the mother possesses the rare ability to change the tension on the secreted thread, which alters the proximity of the egg with respect to her body. In this study, we used behavioral observations, confocal microscopy, and transmission electron microscopy to study the functional morphology of the stalk gland, which secretes a similar thread to the style gland. Our observations reveal that six longitudinal muscles insert on a stalk-gland complex, which is a combination of a two-headed gland and an epithelial duct that connects to the posterior cloaca. The gland secretes a single, long, electron-dense thread that traverses the duct and attaches to the egg surface through the cloaca. Three retractor muscles insert on the stalk gland and function to pull the entire complex anteriorly, thereby increasing tension on the thread and moving the egg close to the mother's body. A set of three (two pairs and a single dorsal) protractor muscles antagonize these actions, and their contraction pulls the gland complex close to the cloaca, thereby releasing tension on the thread and allowing the egg to distance itself from the mother. The stalk gland complex does not appear to be homologous to the style glands of other rotifers, but we hypothesize that it functions as a form of maternal protection as is the case with style glands.

REPRODUCTIVE ABILITY OF BEE QUEENS AND PRODUCTIVITY OF BEES FEEDING MAGNESIUM CITRATES

The research was conducted on two groups of bees families-analogs, three families in each group. Bees of the control (I) group were fed with 60% of sugar syrup (s.s) in the amount of 2 l / family / week. Bees of the II (experimental) group with 2 l of s.s. received 4 mcg/ml of Mg in the form of citrate obtained by the nanotechnology method from LLC Nanomaterials and Nanotechnologies, Kyiv. Indicators of bee queens egg laying intensity was determined by the method of counting the amount of number of sealed brood. Samples of bee body tissues and honey were investigated, in which the content of individual heavy metals (Fe, Сu, Zn) was determined on an atomic absorption spectrophotometer SF-115 PC, as well as the qualitative indicators of honey. According to the results of the researches during the entire research period bee queens of the control (1st), 2nd research groups oviposited 47783 and 49721 eggs, respectively. Probable inter group differences of egg laying were marked at feeding bee families pure sugar syrup and with adding to it citrates Mg. Amount of oviposited eggs in the 2nd research groups during the research period was higher accordingly by 1,4 % in comparison to the control group. Research results specify on expediency of application of citrates of Mg for stimulation of vital functions of bee colony and increasing the reproductive ability of queen bees during their intensive egg laying
 Researches have shown changes in the correlation of trace elements in body tissues of bees with an increase in the content of Fe, Cu and a decrease in the concentration Zn. Feeding of bees with Mg citrates caused an increase parameters of honey, as evidenced by the probable increase in diastasis number and proline content in honey of bees of the experimental groups. Organoleptic characteristics of honey when feeding bees with Mg citrates did not change significantly in the experimental groups compared with the control and met the current standards of DSTU 4497: 2005. It is concluded that feeding bees with the addition to sugar syrup Mg nanotechnological citrates stimulates the intensity of egg laying by queen bees, mineral exchange in their organism and optimizes the content of trace elements and quality indicators in products.

Cross-breeding of Tenebrio molitor strains from a large-scale perspective

Abstract To meet the increased future needs in insect Processed Animal Proteins PAPs, insect sector has to optimize the mass rearing of insects. That being the case, a means to tackle this growing demand for insects is to invest in breeding strategies aiming for the production of hybrids with improved economically and biologically valuable traits. In this framework, the objective of the present study was to evaluate the mating compatibility among four strains of the yellow mealworm, Tenebrio molitor, from different geographical areas (Greece, Belgium, Italy and USA) and to assess and compare the performance of the produced inbred and partially outbred lines. All trials were performed in crates of the size (40 × 60 cm) typically used in industrial rearing of mealworm. Adults of T. molitor were placed in the crates and were left to mate and oviposit. To assess mating compatibility, the amount of oviposited eggs (g) as well as the larval hatching rate were recorded. For the assessment of larval performance of inbred and partially outbred lines, two to three weeks old larvae were placed in crates together with Insectus as feeding substrate. The results showed that all crossed lines demonstrated compatibility, and certain combinations outperformed others as suggested by the high cumulative number of eggs and the larval hatch rates for both inbred and partially outbred lines produced. For hatched larvae, there were significant differences among the inbred and partially outbred lines. The highest hatch rates recorded for the Italian-Italian, Belgian-Italian, and Belgian-USA lines. Concerning offspring performance, all crosses followed a similar pattern in terms of final larval weight. The present study aims to draw the attention of the scientific community and insect producing companies to cross-breeding practices to start unfolding its potential for the genetical improvement of commercially farmed insects.

The ootheca of Libyaspis flavosparsa (Montandon) (Heteroptera: Plataspidae), with a review of ootheca-production in Heteroptera and other Insecta

Parental care behaviours including the defence of oviposited eggs are common strategies to increase the fitness of offspring in animals. Among insects, Hemiptera, the true bugs (Heteroptera) and allies, show a wide range of such strategies. Females of some heteropteran species in the family Plataspidae, in addition to standard maternal care of eggs and early instar nymphs, provide protection of eggs by forming an ootheca, a complex structure coating the egg batch. Although not homologous across the insect taxa in which oothecae occur, structures referred to as oothecae are relatively common in insects, but the literature has so far not been summarized comprehensively. The goals of the present study are twofold. First, we provide a detailed description of the egg and ootheca of the tropical plataspid species Libyaspis flavosparsa (Montandon). The oothecal material of Plataspidae originates from a modified epithelium of the midgut thus represents a unique situation within all insects. Second, the known occurrences of oothecae in Insecta are summarized and discussed. This study provides a basis for future investigations both into the ootheca in Heteroptera and in other insects.

Development and reproductive potential of Plutella xylostella (Lepidoptera: Plutellidae) in five Brassicaceae hosts

Plutella xylostella (L.) is one of the main pests in Brassicaceae crops, although, information regarding its biology on alternative hosts is scarce, crucial for its mass rearing. We studied the development, biology, and population parameters of P. xylostella, fed with different Brassicaceae. In laboratory conditions, P. xylostella was reared from larva 1 to adult. Larvae were fed with B. napus (rapeseed), Brassica carinata (Ethiopian rape), Brassica oleracea var. capitata (cabbage), Rapistrum rugosum (turnipweed) and Raphanus raphanistrum (radish). The development time of immature stages was longer in B. oleracea var. capitata (19.19 ± 0.43d) and shorter in R. raphanistrum (15.44 ± 0.37d). In R. rugosum, the highest survival of individuals that reached adult stage was achieved. The highest value of oviposited eggs was recorded in R. rugosum (300.82 ± 24), and highest hatching percentage in R. raphanistrum (79.7%). The highest values of net reproductive rate, intrinsic rate of increase and finite rate of growth, were obtained with R. rugosum. P. xylostella complete their whole cycle in any of the five hosts, being R. rugosum most suitable host for an efficient mass rearing system.

Determination of Silicon Accumulation in Non-Bt Cotton (Gossypium hirsutum) Plants and Its Impact on Fecundity and Biology of Whitefly (Bemisia tabaci) under Controlled Conditions

Considering the resistance development-potential of whitefly (Bemisia tabaci) against control tactics with limited action mechanisms, the present study investigated the accumulation of two different silicon (Si) sources (SiO2 and K2SiO3) in cotton plants. The tested dose rates (0, 200, and 400 mg/L) of both Si sources were applied directly to the soil or through foliar application on cotton leaves. Moreover, a laboratory bioassay was also conducted to evaluate the performance of applied Si sources against the oviposition preference and biology of B. tabaci. A significantly higher Si accumulation, reduction in oviposition preference, and prolonged developmental period of all nymphs and total life cycle of B. tabaci was observed in the case of foliar-applied silicon. Similarly, among Si sources, a significant decline in the number of oviposited eggs and delay in the developmental period of B. tabaci was observed in the case of SiO2, followed by K2SiO3. Moreover, cotton plants subjected to SiO2 treatments possessed higher Si contents in their leaves than K2SiO3 treated plants. The results further revealed that both Si sources showed promising results at their higher concentrations regarding the tested parameters of Si accumulation, fecundity, and developmental period of B. tabaci. Our results strongly suggest that among emerging pest control strategies in cotton plants lies the use of foliar application of Si, which can also be incorporated in different integrated pest management programs due to its safety for humans and beneficial insect fauna.

Inheritance of the duration of fertility in chickens and its correlation with laying performance

BackgroundDuration of fertility (DF) is an important economic trait in poultry production because it has a strong effect on chick output. Various criteria or traits to assess DF on individual hens have been reported but they are affected by many nongenetic factors. Thus, a reliable definition and associated genetic parameters are needed. Because egg production is also vital in chicken breeding, knowledge of the relationship between DF and laying performance is needed for designing selection programs.MethodsWe used five traits that consider both fertility and embryonic livability to delineate DF. Phenotypic and genetic analyses were completed for 2094 hens, with measurements of DF at 35 and 60 weeks of age and hatching egg production at 400 days of age (HEP400). The selection differentials for DF and HEP400 were evaluated.ResultsDF is largely independent of the number of oviposited eggs in the peak laying period but both egg production and DF naturally decline with age. The heritability of the five DF traits ranged from 0.11 to 0.13 at 35 weeks of age and increased slightly in the later laying period, ranging from 0.14 to 0.17 (except for efficient duration, time between insemination and the first unhatched egg). Estimates of the genetic correlation for a given trait measured at the two ages were moderate (0.37–0.44), except for efficient duration. However, number of viable embryos depends strongly on egg production. Estimates of genetic correlations of fertility duration day (FDD) at both ages with HEP were weak. Selection for FDD improved DF but without a significant change in laying performance. Selection for increased HEP400 did not contribute to DF improvement.ConclusionsAlthough estimates of heritability of the five traits related to DF were low, selection to improve DF based on any one of them is possible. Among these, FDD is an effective selection criterion when the eggs are collected for approximately two weeks after insemination. The best selection procedure for DF improvement would involve multiple measurements at various ages. FDD is independent of laying performance and can be incorporated into a breeding program with egg production to improve reproductive efficiency.

Insulin peptides and their receptors regulate ovarian development and oviposition behavior in Diaphorina citri.

Diaphorina citri is an important vector of Citrus Huanglongbing (HLB) disease. After feeding on young host plant shoots, the population of D.citri can increase significantly. Females also only lay eggs on young shoots. However, there are few studies on the mechanism of this phenomenon. Exogenous nutrient signals can affect the insulin signaling system of D.citri after feeding on young shoots. In this study, the expression of upstream factors DcILP1, DcILP2, and DcIR in the insulin signaling system of D.citri was upregulated after feeding on young shoots. After being silenced by RNA interference technology, the results showed that the number of oviposited eggs of D.citri was significantly decreased and the ovarian development was inhibited with severe vacuolation. In addition, detection using quantitative reverse transcription-polymerase chain reaction showed that the upstream regulatory gene DcRheb of the target of rapamycin (TOR) pathway and the downstream reproduction-related DcVg gene were also significantly downregulated. These results suggest that feeding upon young shoots may upregulate the expression levels of upstream factors DcILP1, DcILP2, and DcIR in the insulin signaling system. The signal will be through upregulating the expression of DcRheb, an upstream gene of the TOR signaling pathway. This in turn influences yolk metabolism, which eventually causes the ovaries of female D.citri to mature and therefore initiate oviposition behavior.

Selección de Resistencia y Efectos Subletales de Cipermetrina en la Palomilla Dorso de Diamante (Plutella xylostella L.)

Plutella xylostella es una importante plaga de cultivos de brassicas en más de 100 países. El principal método de control de P. xylostella se basa en el uso de insecticidas químicos. Sin embargo, esta especie se caracteriza por su rápido desarrollo de resistencia a casi todos los insecticidas. Se ha reportado que la aplicación de concentraciones bajas de insecticidas afecta la fisiología, bioquímica y ecología de los insectos. En este estudio, se realizó una selección de resistencia de cipermetrina durante ocho generaciones de P. xylostella y se determinó la dosis subletal (CL20) de la línea resistente y de la línea susceptible. Posteriormente, la dosis subletal se aplicó a larvas de tercer instar para investigar su efecto en el porcentaje de pupación, peso de pupas, emergencia de adultos en dos generaciones (progenitores y descendientes), así como los tiempos de desarrollo de cada fase de desarrollo de P. xylostella. Se observó una disminución el porcentaje de pupas formadas, adultos emergidos y peso de pupas. Por otro lado, el número de huevos depositados aumentó cuando los individuos fueron expuestos al insecticida. Lo anterior puede ser un factor importante para el manejo y control de esta plaga cuando se presenten problemas de resistencia a cipermetrina.

Fitness Costs of Chlorantraniliprole Resistance Related to the SeNPF Overexpression in the Spodoptera exigua (Lepidoptera: Noctuidae).

Spodopteraexigua, a multifeeding insect pest, has developed a high level of resistance to chlorantraniliprole, which is a benzoylurea insecticide that targets the ryanodine receptors (RyRs). Herein, the resistant strain (SE-Sel) and sensitive strain (SE-Sus) were obtained by bidirectional screening for six generations. The potential oviposited eggs and oviposition rate of the SE-Sel strain were dramatically lower than those of the SE-Sus strain; on the contrary, the weights of prepupae and preadult were significantly increased. As a post-mating response, the higher number of non-oviposited eggs in the SE-Sel strain was caused by a lower mating rate. In addition, the expression levels of vitellogenin (SeVg) and its receptor (SeVgR) in the SE-Sel strain were consistently lower than those in the SE-Sus strain. An RyRI4743M mutation, contributing to the resistance to chlorantraniliprole, was located in the S3 transmembrane segments and might have affected the release of calcium ions; it led to the upregulated expression of the neuropeptide SeNPF and its receptor SeNPFR, and the mating and oviposition rate were significantly recovered when the SeNPF was knocked down though RNA interference (RNAi) in the male adult of the SE-Sel strain. Moreover, the expression of the juvenile hormone-binding proteins SeJHBWDS3 and SeJHBAN in the male adult of the SE-Sel strain was significantly decreased, which proved the existence of a fitness cost from another angle. Therefore, these results indicate that the fitness cost accompanied by chlorantraniliprole resistance in S. exigua may be related to the decrease in mating desire due to SeNPF overexpression.

Chorion exploration in the tribe Anthocharidini (Lepidoptera: Pieridae) and their possible importance in its systematics.

We describe and compare the morphology of the chorion in nine species belonging to five genera of the tribe Anthocharidini (Pieridae: Pierinae), from a sample of 12 females with mature eggs, the bibliographic record of oviposited eggs, and photographs of scanning electron microscopy (SEM). The eggs examined come from Mexico, Spain, Brazil and Costa Rica. Its characterization was made considering the main structural features of the chorion in this tribe; it includes a distinction of structures in the apical zone and differentiation between the chorionic regions. We attached to this work sheets, diagrams, and terminology to understand and clarify the descriptions. Our results agree with the proposal of Anthocharidini as the least derived tribe of the Pierinae, considering that Hebomoia, a specialized genus, is not part of it. Tribes such as Leptosiaini, Elodinini or Nepheroniini also have more chorionic characteristics related to more derived tribes of the Pierinae.

Effect of silicon on tritrophic interaction of cotton, Gossypium hirsutum (Linnaeus), Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) and the predator, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae)

The development of resistance in Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) against a number of conventional and new chemistry insecticides has encouraged researchers to exploit some eco-friendly integrated pest management approaches to keep the pest population below their threshold levels. In the current laboratory trials, a free choice cotton leaf-disc assay was conducted to check the effect of silicon on oviposition preference of B. tabaci. Moreover, a predator–prey bioassay was also conducted to compare the developmental and reproductive traits of the predator, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) when offered B. tabaci that had either been fed on silicon-treated or untreated cotton plants. The results indicate that silicon treatments significantly reduced the oviposition preference of B. tabaci, however, a more profound effect was observed in the case of foliar applications of silicon as compared to its drenching treatments. Similarly, leaf discs harvested from plants treated with SiO2 showed a significant decline in the number of oviposited eggs as compared to K2SiO3 treatments. However, silicon application did not induce any indirect negative effect on the developmental and reproductive traits of the predator, C. carnea except for its fecundity which might be affected due to feeding on poorer quality host. The current results suggest that feeding of silicon exposed prey does not inflict any direct harmful effects on the biology of predator, C. carnea, hence their integration can be a promising crop protection strategy to encounter the challenges of resistance development in B. tabaci.

Mass production of a S-layer protein of Bacillus thuringiensis and its toxicity to the cattle tick Rhipicephalus microplus

The most commonly used biopesticides to control agricultural, forest and insect vectors of human diseases are derived from the bacterium Bacillus thuringiensis, which begins to produce Cry and Cyt insecticidal proteins during the onset of the sporulation phase. Some B. thuringiensis strains also produce S-layer proteins that are toxic to certain pests. S-layer proteins are the most abundant proteins in bacteria and archaea. This proteins’ key trait to design high performace processes for mass production is their continuous expression during the vegetative phase, unlike Cry and Cyt, which are restricted to the sporulation phase. In this work, a S-layer protein expressed by the GP543 strain of B. thuringiensis that is toxic to the cattle tick Rhipicephalus microplus was mass produced using the batch culture fermentation technique. In addition, the spore-protein complex showed a mortality rate of 75% with a dose of 300 µg·mL−1 on adult females of R. microplus after fourteen days. The lethal concentration 50 was 69.7 µg·mL−1. The treatment also caused a decrease of 13% in the weight of the mass of oviposited eggs with 200 µg·mL−1 of the spore-protein complex and inhibition of the hatching of eggs from 80 to 92%. Therefore, this could be a good option for controlling this parasite. The advantages of S-layer protein synthesis are focused on the production of a new generation of proteins in pest control. This is the first report on the mass production of an S-layer protein that is responsible for toxicity.

Direct and transgenerational effects of an experimental heatwave on early life stages in a freshwater snail

Abstract Global climate change imposes a serious threat to natural populations of many species. Estimates of the effects of climate change‐mediated environmental stresses are, however, often based only on their direct effects on organisms, and neglect the potential transgenerational (e.g. maternal) effects. We tested whether high temperature (i.e. an experimental heatwave), which is known to reduce the performance of adult Lymnaea stagnalis snails, affects the produced offspring (eggs and hatchlings) through maternal effects, and how strong these effects are compared with the effects of direct exposure of offspring to high temperature. We examined the effect of maternal thermal environment (15°C versus 25°C) on per offspring investment (egg size), and the role of both maternal and offspring thermal environments (15°C versus 25°C) on hatching success and developmental time of eggs, offspring survival after hatching, and hatchling size at the age of 5 weeks. Exposure of mothers to high temperature reduced the size of oviposited eggs, increased their hatching success, and also made the onset of hatching earlier. However, high maternal temperature reduced the survival and the final size of hatched juveniles. Direct exposure of offspring to high temperature reduced their survival (both eggs and hatchlings) but increased the developmental rate and growth of those individuals that survived. Interestingly, the magnitude of maternal effects on hatching success of eggs and hatchling survival were similar to the direct effects of high temperature. Our results indicate that heatwaves can affect natural populations through transgenerational maternal effects and that the magnitude of those effects can be equally strong to the direct effects of temperature, although this depends on the trait considered. These findings highlight the importance of considering the transgenerational effects of climate warming when estimating its effects in the wild.

Variations in fecundity over catchment scales: Implications for caddisfly populations spanning a thermal gradient

Abstract Population sizes of stream insects depend on the number of eggs that enter the benthos. Densities of oviposited eggs have been linked to densities of oviposition habitat, but variability in fecundity has not been explored. Fecundity may differ between sites where females experience different thermal environments during development, because insects generally grow larger and produce more eggs in cold places (e.g. high elevation and latitude). We predicted that because the fecundity of emerging females should increase with elevation then the numbers of eggs in oviposited egg masses (clutch sizes) should also increase with elevation. Alternatively, individuals may routinely disperse along channels or between rivers, mixing individuals that have grown and developed in different thermal environments, in which case clutch sizes may not vary with elevation but could vary greatly within sites. We tested these hypotheses across an elevation gradient of 250–1,080 m above sea level, in seven streams in southeast Australia. We surveyed the fecundity of three species of caddisflies (Trichoptera: Hydrobiosidae) in 2009 (eight sites) and 2010 (17 sites). Female hydrobiosids attach their entire clutch of eggs to an emergent stream boulder, in a single egg mass. At each site we censused the number of egg masses in two random 50 m stretches and photographed a sample of egg masses. Clutch sizes were quantified by counting eggs from the photographs. From numbers of egg masses and mean clutch size per site, we estimated the number of individual eggs per site, to determine whether spatial differences in clutch size affect patterns of egg supply. Potential trade‐offs between egg number and size were also examined. Strong thermal gradients were observed in both years. Sites at lowest elevations were 4.8°C (2009) and 3.6°C (2010) warmer than sites at highest elevations, and accumulated 392 (2009) and 361 (2010) more degree‐days (>0°C) over a period of 88 days. Clutch sizes of each species varied markedly within and between species but did not differ along the thermal gradient. Within species, 83.7–93.7% of variation in clutch size was expressed within sites. Relatively little variation occurred between sites or rivers. Within species, counts of egg masses adequately described relative egg supply to each site, because clutch sizes were similar between sites and rivers. Comparing egg supply between species, however, required including clutch sizes to estimate supply. Egg size differed within but not between species. Significant but small variations in egg size were trivial compared to much larger variations in clutch size. Our results suggest that any spatial differences in fecundity caused by temperature may be erased by dispersal, such that females from multiple locations mix between sites prior to oviposition. A warming global climate may reduce the fecundity of ectotherms such as aquatic insects but consequences for populations are difficult to predict. Moreover, climate‐related effects on fecundity may not be apparent when dispersal by individuals between elevations mixes any effects of climate change on fecundity.

Nutrient Content of Brown Marmorated Stink Bug Eggs and Comparisons Between Experimental Uses

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), the brown marmorated stink bug (BMSB), has become a major pest. Seven experiments examined the nutrient content of their eggs in the context of female reproductive investment and use for experiments. Among 542 clusters examined, an average egg contained 23.50 ± 0.561 µg lipid, 3.17 ± 0.089 µg glycogen, and 3.08 ± 0.056 µg sugar. Mature eggs within a female’s ovary can make up 61% of her total lipid, 35% of glycogen, and 20% of sugar levels. Eggs obtained from a colony reared on a steady diet are expected to have consistent nutrient content. The age of a parental female only slightly affected the lipid level of oviposited eggs but did not affect glycogen or sugar levels. However, egg nutrient content can differ substantially by the source of the parental females; wild eggs had higher lipid but lower sugar content than colony-produced eggs. Further, the length of time that eggs are frozen influenced egg nutrient content. Freshly laid eggs had higher lipid and lower sugar levels than eggs frozen for 1 or 2 yr. Whether an egg turned grey following removal from cold storage did not affect nutrient content, nor did being frozen within 1 or 3 d of oviposition. The temperature at which eggs were left exposed did not impact egg nutrient content, but glycogen decreased and sugar increased with deployment time. This information combined with how factors affect host selection by natural enemies will help refine future experiments that use BMSB egg clusters.

Filling gaps on ivermectin knowledge: effects on the survival and reproduction of Anopheles aquasalis, a Latin American malaria vector.

BackgroundStrategies designed to advance towards malaria elimination rely on the detection and treatment of infections, rather than fever, and the interruption of malaria transmission between mosquitoes and humans. Mass drug administration with anti-malarials directed at eliminating parasites in blood, either to entire populations or targeting only those with malaria infections, are considered useful strategies to progress towards malaria elimination, but may be insufficient if applied on their own. These strategies assume a closer contact with populations, so incorporating a vector control intervention tool to those approaches could significantly enhance their efficacy. Ivermectin, an endectocide drug efficacious against a range of Anopheles species, could be added to other drug-based interventions. Interestingly, ivermectin could also be useful to target outdoor feeding and resting vectors, something not possible with current vector control tools, such as impregnated bed nets or indoor residual spraying (IRS).ResultsAnopheles aquasalis susceptibility to ivermectin was assessed. In vivo assessments were performed in six volunteers, being three men and three women. The effect of ivermectin on reproductive fitness and mosquito survivorship using membrane feeding assay (MFA) and direct feeding assay (DFA) was assessed and compared. The ivermectin lethal concentration (LC) values were LC50 = 47.03 ng/ml [44.68–49.40], LC25 = 31.92 ng/ml [28.60–34.57] and LC5 = 18.28 ng/ml [14.51–21.45]. Ivermectin significantly reduced the survivorship of An. aquasalis blood-fed 4 h post-ingestion (X2 [N = 880] = 328.16, p < 0.001), 2 days post-ingestion (DPI 2) (X2 [N = 983] = 156.75, p < 0.001), DPI 7 (X2 [N = 935] = 31.17, p < 0.001) and DPI 14 (X2 [N = 898] = 38.63, p < 0.001) compared to the blood fed on the untreated control. The average number of oviposited eggs per female was significantly lower in LC5 group (22.44 [SD = 3.38]) than in control (34.70 [SD = 12.09]) (X2 [N = 199] = 10.52, p < 0.001) as well as the egg hatch rate (LC5 = 74.76 [SD = 5.48]) (Control = 81.91 [SD = 5.92]) (X2 [N = 124] = 64.24, p < 0.001). However, no differences were observed on the number of pupae that developed from larvae (Control = 34.19 [SD = 10.42) and group (LC5 = 33.33 [SD = 11.97]) (X2 [N = 124] = 0.96, p > 0.05).ConclusionsIvermectin drug reduces mosquito survivorship when blood fed on volunteer blood from 4 h to 14 days post-ingestion controlling for volunteers’ gender. Ivermectin at mosquito sub-lethal concentrations (LC5) reduces fecundity and egg hatch rate but not the number of pupae that developed from larvae. DFA had significantly higher effects on mosquito survival compared to MFA. The findings are presented and discussed through the prism of malaria elimination in the Amazon region.

Tetracycline-suppressible female lethality and sterility in the Mexican fruit fly, Anastrepha ludens.

The sterile insect technique (SIT) involves the mass release of sterile males to suppress insect pest populations. SIT has been improved for larval pests by the development of strains for female-specific tetracycline-suppressible (Tet-off) embryonic lethal systems for male-only populations. Here we describe the extension of this approach to the Mexican fruit fly, Anastrepha ludens, using a Tet-off driver construct with the Tet-transactivator (tTA) under embryo-specific Anastrepha suspensa serendipity α (As-sry-α) promoter regulation. In the absence of tetracycline, tTA acts upon a Tet-response element linked to the pro-apoptotic cell death gene lethal effector, head involuation defective (hid), from A. ludens (Alhid(Ala2) ) that contains a sex-specific intron splicing cassette, resulting in female-specific expression of the lethal effector. Parental adults double-homozygous for the driver/effector vectors were expected to yield male-only progeny when reared on Tet-free diet, but a complete lack of oviposited eggs resulted for each of the three strains tested. Ovary dissection revealed nonvitellogenic oocytes inall strains that was reversible by feeding females tetracycline for 5 days after eclosion, resulting in male-only adults in one strain. Presumably the sry-α promoter exhibits prezygotic maternal expression as well as zygotic embryonic expression in A. ludens, resulting in a Tet-off sterility effect in addition to female-specific lethality.

Behavioral Responses of Nymph and Adult Cimex lectularius (Hemiptera: Cimicidae) to Colored Harborages.

Behavioral bioassays were conducted to determine whether bed bug adults and nymphs prefer specific colored harborages. Two-choice and seven-choice behavioral color assays indicate that red (28.5%) and black (23.4%) harborages are optimal harborage choices for bed bugs. Yellow and green harborages appear to repel bed bugs. Harborage color preferences change according to gender, nutritional status, aggregation, and life stage. Female bed bugs prefer harborages with shorter wavelengths (lilac-14.5% and violet-11.5%) compared to males, whereas males prefer harborages with longer wavelengths (red-37.5% and black-32%) compared with females. The preference for orange and violet harborages is stronger when bed bugs are fed as opposed to when they are starved. Lone bed bugs (30%) prefer to be in black harborages while red harborages appear to be the optimum harborage color for bed bugs in more natural mixed aggregations (35.5%). Bed bug nymphs preferred different colored harborages at each stage of development, which is indicative of their developing eye structures and pigments. First instars showed no significant preference for any colored harborage soon after hatching. However, by the fifth instar, 27.5% of nymphs significantly preferred red and black harborages (which was a similar preference to adult bed bugs). The proportion of oviposited eggs was significantly greater under blue, red, and black harborages compared to other colored harborages tested. The use of visual cues such as specific colors offers great potential for improving bed bug monitoring tools by increasing trap captures.

Larval food influences temporal oviposition and egg quality traits in females of Lobesia botrana

Many phytophagous insects are agricultural pests, and control methods require accurate monitoring and decisions based on the determination of population age structure. The reproductive output (fecundity, egg size and percent egg hatch) is a central life history trait because it determines the offspring number, and temporal oviposition patterns are of primary importance in conditioning larval hatching and the occurrence of later larval instars in time. In turn, these phenomena determine the window for natural enemy attack and thus impact the context of biological control programmes. In addition, for most phytophagous insects, the quality of the host plants that larvae consume determines the insects’ reproductive output. The purpose of the present study was to determine whether the number of eggs laid, egg size and egg hatch percentage vary with female age and the cultivar on which females develop as larvae, as well as the temporal effects of these parameters. This determination was performed in laboratory experiments where larvae were reared on artificial diets based on dried fruits of seven cultivars. Our results showed that the cultivars had a significant effect on female temporal oviposition. Independent of the food tested, the numbers of oviposited eggs, their size and percent egg hatch decreased with daily oviposition rank. Such temporal patterns must be incorporated in age-structured mathematical models used in the design of control strategies. Temporal oviposition and variation in egg quality traits will also be useful in biological control programmes, especially when based on egg or larval parasitoids, which is thus discussed.