Transmission of the Diachasmimorpha longicaudata rhabdovirus (DlRhV) to wasp offspring: an ultrastructural analysis

During oviposition, the parasitic wasp Diachasmimorpha longicaudata introduces an entomopoxvirus (DlEPV) and a rhabdovirus (DlRhV) into larvae of its tephritid fruit fly host Anastrepha suspensa. DlEPV and DlRhV replicate, respectively, in host hemocytes and epidermal cells. Both viruses, like many beneficial viruses of parasitic wasps, are retained in all wasp generations but their avenue(s) of transmission are unknown. This study tests the hypothesis that DlRhV is transmitted transovarially or through larval feeding on infected host hemolymph. Transmission electron microscopy (TEM) revealed no virions in pre-vitellogenic or vitellogenic ova, or in the lateral oviduct of D. longicaudata females. However, numerous virions occurred in subchorionic regions of 33-36-h-old oviposited eggs. This suggests that DlRhV is introduced into the egg either as (a) intact virions after chorionogenesis but prior to oviposition and/or as (b) unencapsidated RNA molecules, undetectable by TEM in pre-vitellogenic ova, that subsequently replicate and assemble into mature virions. DlRhV particles also occurred in the midgut lumen of 20-24-h-old wasp first instars, suggesting that they were ingested. These virions may have been released from the egg into the hemolymph during hatching or may have come from virions introduced by the female wasp directly into the host, separate from the egg. DlRhV particles were also evident in the intracellular vesicles and intercellular spaces of the larval midgut. Taken together, these data support the hypothesis that DlRhV is transovarially transmitted as virions and/or as unencapsidated RNA. Further studies are needed to determine whether the DlRhV that ultimately resides within the female wasp's accessory gland filaments is the progeny of the virus from the egg and/or larval midgut cells.     

Uptake of bovine IgG by first instars of the common cattle grub, Hypoderma lineatum

The midgut of first instar Hypoderma lineatum (De Vill.) (Diptera: Oestridae) was examined for the presence of bovine immunoglobulin using immuno-gold staining in conjunction with image analysis. Newly hatched larvae, unexposed to fluids or tissues of the host, showed little or no deposit of colloidal gold particles. Midgut lumen, microvillar border, epithelial cell bodies and basement membrane of first instars, 6-7 months of age, recovered from the host oesophagus, all showed colloidal gold staining. This indicates that immuno-reactive portions of bovine immunoglobulin survive exposure to extracorporeal larval enzymes, as well as transit of the midgut, and pass through epithelial cells to enter the larval haemocoel.     

Developmental strategy of the endoparasite Xenos vesparum (strepsiptera, Insecta): host invasion and elusion of its defense reactions

To successfully complete its endoparasitic development, the strepsipteran Xenos vesparum needs to elude the defense mechanisms of its host, the wasp Polistes dominulus. SEM and TEM observations after artificial infections allow us to outline the steps of this intimate host-parasite association. Triungulins, the mobile 1st instar larvae of this parasite, are able to "softly" overcome structural barriers of the larval wasp (cuticle and epidermis) without any traumatic reaction at the entry site, to reach the hemocoel where they settle. The parasite molts 48 h later to a 2nd instar larva, which moves away from the 1st instar exuvium, molts twice more without ecdysis (a feature unique to Strepsiptera) and pupates, if male, or develops into a neotenic female. Host encapsulation involves the abandoned 1st larval exuvium, but not the living parasite. In contrast to the usual process of encapsulation, it occurs only 48 h after host invasion or later, and without any melanization. In further experiments, first, we verified Xenos vesparum's ability to reinfect an already parasitized wasp larva. Second, 2nd instar larvae implanted in a new host did not evoke any response by hemocytes. Third, we tested the efficiency of host defense mechanisms by implanting nylon filaments in control larval wasps, excluding any effect due the dynamic behavior of a living parasite; within a few minutes, we observed the beginning of a typical melanotic encapsulation plus an initial melanization in the wound site. We conclude that the immune response of the wasp is manipulated by the parasite, which is able to delay and redirect encapsulation towards a pseudo-target, the exuvia of triungulins, and to elude hemocyte attack through an active suppression of the immune defense and/or a passive avoidance of encapsulation by peculiar surface chemical properties.     

Growth and development of Encarsia formosa (Hymenoptera: Aphelinidae) in the greenhouse whitefly, Trialeurodes vaporariorum (Homoptera: Aleyrodidae): effect of host age

The tiny parasitoid wasp, Encarsia formosa, has been used successfully to control greenhouse whiteflies (GHWFs) in greenhouses in many countries throughout the world. Therefore, there has been considerable interest in developing methods for artificially rearing this wasp. However, little information is available concerning the regulation of its development including the host-parasitoid interactions that are required for the parasitoid to complete its life cycle. Here we confirm that parasitoid developmental rates differ significantly based upon the host instar parasitized. Development was faster when 3rd and 4th instar GHWFs were offered for parasitization than when 1st or 2nd instars were used. Our results show that it is primarily the embryo and the first two parasitoid instars that exhibit prolonged developmental times when 1st and 2nd instar whiteflies are parasitized. Although percent emergence was not affected by host age at the time of parasitization, adult longevity as well as adult emergence pattern varied greatly depending upon the instar parasitized. When 3rd and 4th instar GHWFs were selected for oviposition, adult wasps lived significantly longer than when 1st or 2nd instars were used; also, there was a sharp emergence peak on the 2nd day after emergence was first observed (reduced or absent when 1st or 2nd instar GHWFs were parasitized) and the emergence period was reduced from between 8 and 11 days to 5 days. In general, the younger the host instar parasitized, the less synchronous was parasitoid development. Previous reports that E. formosa will not molt to the 2nd instar until the host has reached its 4th instar were not confirmed. When 1st instar host nymphs were parasitized, 2nd instar parasitoids were detected in 3rd instar hosts. Importantly, however, no matter which instar was parasitized, the parasitoid never molted to its last instar until the host had reached Stage 5 of its last instar, a stage in which host pharate adult formation has been initiated. It appears, then, that a condition(s) associated with host pharate adult formation is required for the parasitoid's final larval molt. Results reported here should facilitate the development of in vitro rearing systems for E. formosa.     

Inhibition of juvenile hormone esterase activity in Lymantria dispar (Lepidoptera, Lymantriidae) larvae parasitized by Glyptapanteles liparidis (Hymenoptera, Braconidae)

Glyptapanteles liparidis is a gregarious, polydnavirus (PDV)-carrying braconid wasp that parasitizes larval stages of Lymantria dispar. In previous studies we showed that parasitized hosts dramatically increase juvenile hormone (JH) titers, whereas JH degradation is significantly inhibited in the hemolymph. Here we (i) quantified the effects of parasitism on JH esterase (JHE) activity in hemolymph and fat body of penultimate and final instars of L. dispar hosts and (ii) assessed the relative contribution of individual and combined wasp factors (PDV/venom, teratocytes, and wasp larvae) to the inhibition of host JHE activity. The effects of PDV/venom was investigated through the use of gamma-irradiated wasps, which lay non-viable eggs (leading to pseudoparasitization), while the effects of teratocytes and wasp larvae were examined by injection or insertion of these two components in either control or pseudoparasitized L. dispar larvae. Parasitism strongly suppressed host JHE activity in both hemolymph and fat body irrespective of whether the host was parasitized early (premolt-third instar) or late (mid-fourth instar). Down-regulation of JHE activity is primarily due to the injection of PDV/venom at the time of oviposition, with only very small additive effects of teratocytes and wasp larvae under certain experimental conditions. We compare the results with those reported earlier for L. dispar larvae parasitized by G. liparidis and discuss the possible role of JH alterations in host development disruption.     

Morphology of the female Myrmecolacidae (Strepsiptera) including the apron, and an associated structure analogous to the peritrophic matrix

Development in the totally endoparasitic female Strepsiptera has been clarified by light and electron microscopy. At the end of the 4th instar the cuticle sclerotizes anteriorly to form the cephalothorax and collar, the former of which is later extruded through the host cuticle. Posteriorly, the cuticle remains unsclerotized, and this region is within the host. The moult to the neotenic adult takes place within the 4th instar cuticle, and the epicuticles of the previous instars are retained as persistent sheaths. The gut, which is present in the earlier endoparasitic stages, is lost after extrusion of the cephalothorax, and a novel structure develops on the ventral surface of the neotenic female. Due to the position of this novel structure in the neotenic female, this area is called an apron. The detailed structure of the membranes in the apron in Stichotrema dallatorreanum Hofeneder from Oro Province, and of another female myrmecolacid (which has a different host) from West New Britain in Papua New Guinea, is described. A dual function for the apron is proposed.     

Biology of Microplitis kewleyi (Hymenoptera: Braconidae): A parasite of Agrotis ipsilon (Lepidoptera: Noctuidae) larvae

Microplitis kewleyi Muesebeck is a gregarious internal parasite of larvae of the black cutworm Agrotis ipsilon (Hufnagel). Studies of the biology of the parasite revealed that there was an inverse relationship between host instar and parasite preference. Duration of development from egg to pupa ranged from 18 days at 27°C to 68.7 days at 16°C. Development from egg to pupa took 13.5–21.6 days when fourth and first instar host larvae, respectively, were parasitized. A larger number of parasites emerged from hosts parasitized in the fourth instar (22.4) than the first instar (11.5). Parasite pupation occurred when the host was in the fifth/sixth instar, depending on the instar parasitized. Thirty‐nine per cent of host larvae exposed as first instars to parasites died before parasite emergence. This decreased to 0% for host larvae exposed as fourth instars. The sex ratio was 1:1.2 (M:F). Thirty‐seven per cent of hosts exposed diurnally were stung, compared to 24% exposed nocturnally. Mean daily progeny was highest (12) on the first day, decreasing to zero after 20 days. Percent host parasitism was also highest on the first day (35%) decreasing to nearly 0% after 18 days. There appear to be three parasite larval instars. Host larvae often remained alive after parasite emergence.     

Hostplant,larval age,and feeding behavior influence midgut pH in the gypsy moth (Lymantria dispar)

Summary The midgut pH of late instar gypsy moth (Lymantria dispar L.) larvae is strongly alkaline, and varies with diet, larval stadium, and time since feeding. Midgut pH rises with time since feeding, and does so more quickly, reaching greater maximum values, on some diets than others. Leaf tissues of 23 tree species resist increases in alkalinity differentially; this trait and differing initial leaf pH may explain the impact of diet on gut pH. Third instar larvae may have gut conditions favorable for tannin-protein binding shortly after ingesting certain foods, but with time midgut alkalinity becomes great enough to dissociate tannin-protein complexes. Older instars rarely exhibit gut pHs low enough to permit tannin activity. Alkaline gut conditions may explain the gypsy moth's ability to feed on many tanniniferous plant species, especially in later instars. Consequences for pathogen effectiveness are discussed.     

Larval anatomy and structure of absorbing epithelia in the aphid parasitoid Aphidius ervi Haliday (Hymenoptera, Braconidae)

The present work describes Aphidius ervi Haliday (Hymenoptera, Braconidae) larval anatomy and development, focusing on time-related changes of body structure and cell ultrastructure, especially of the epithelial layers involved in nutrient absorption. Newly hatched 1st instar larvae of A. ervi are characterised by gut absence and a compact cluster of cells makes up their body. As the parasitoid larva develops, the central undifferentiated cell mass becomes hollowed out, leading to the formation of gut anlage. This suggests that absorption of nutrients at that stage may take place through the body surface, as more directly demonstrated by the occurrence on the epidermis of proteins associated with transepithelial transport, such as Na(+)/K(+)-ATPase and alkaline phosphatase (ALP). Second instar larvae show the presence of the gut with a well-differentiated brush border and a peritrophic membrane. Gut cells are filled by masses of glycogen granules and lipid droplets. The tracheal system starts to be visible. The haemocoel becomes evident in late 2nd instar, and contains large silk glands. Mature 3rd instar larvae are typically hymenopteriform. The midgut accounts for most of the body volume and is actively involved in nutrient absorption, as indicated by the well developed brush border and by the presence of Na(+)/K(+)-ATPase and ALP on the basolateral and luminal membrane respectively. At this stage, large lipid droplets have gradually replaced the cellular glycogen stores in the midgut cells. The tracheae are completely differentiated, but their internal lumen still contains fibrillar material, suggesting that they are not functional as long as host fluids bath the parasitoid larva. In late 3rd instar larvae, silk glands, structurally similar to Malpighian tubules, show a very intense vesicular traffic toward the internal lumen, which, eventually, results in being filled by secretion products, suggesting the possible recycling of metabolic waste products during mummy formation.     

Ultrastructural and cytochemical aspects of metamorphosis in the midgut of Apis mellifera L. (Hymenoptera: Apidae: Apinae)

The midgut of Apis mellifera is remodeled during metamorphosis. The epithelium and, to a lesser extent, the muscular sheath degenerate between the end of the last larval instar and the onset of pupation (prepupa). The larval epithelium is shed to the midgut lumen and digested, while a new epithelium is reconstructed from larval regenerative cells. During pupation, some reorganization still occurs, mainly in brown-eyed pupae. In pharate adult, the midgut wall shows the characteristics of adult, although some cells have pycnotic nuclei. The localization of alkaline and acid phosphatases showed that these enzymes were not involved in the reabsorption of the midgut wall.     

美丽青背姬小蜂生物学特性研究

美丽青背姬小蜂Chrysonotomyiaformosa（Westwood）是美洲斑潜蝇的优势天敌,在美洲 斑潜蝇的自然控制中发挥着非常重要的作用。本文对其生物学进行了研究,结果表明：在实验 温度范围内,随着温度的升高,寄生蜂羽化趋早,羽化时间更集中,羽化高峰也更明显;随着 温度的升高,成蜂的寿命逐渐缩短。在提供清水时,寄主可以显著地延长雌蜂的寿命;在有寄 主时,提供10%蜂蜜水,雌蜂的寿命显著延长。美丽青背姬小蜂对3龄寄主幼虫有偏好,对3龄寄 主幼虫的致死率和寄生率都高于对1～2龄寄主幼虫的,且产下后代的雌雄性比为5.11∶1。在 实验温度范围内,发育历期随温度的升高而缩短。     

Does superparasitism improve host suitability for parasitoid development? A case study in the Microplitis rufiventris-Spodoptera littoralis system

Superparasitism refers to the oviposition behavior of parasitoid females who lay their eggs in an already parasitized host. Recent studies have shown that allocation of additional eggs to an already parasitized host may be beneficial under certain conditions. In the present work, mortality of Microplitis rufiventris wasps was significantly influenced by both host instar of Spodoptera littoralis larvae at parasitism and level of parasitism. In single parasitization, all host instars (first through sixth) were not equally suitable. Percentage of emergence success of wasp larvae was very high in parasitized first through third (highly suitable hosts), fell to 60% in the fourth instar (moderate suitable) and sharply decreased in the penultimate (5th) instars (marginally suitable). Singly parasitized sixth (last) instar hosts produced no wasp larvae (entirely unsuitable), pupated and eclosed to apparently normal adult moths. The scenario was different under superparasitism, whereas supernumerary individuals in the highly suitable hosts were almost always killed as first instars, superparasitization in unsuitable hosts (4th through 6th) had significant increase in number of emergence success of wasp larvae. Also, significantly greater number of parasitoid larvae successfully developed in unsuitable hosts containing three wasp eggs than counterparts containing two wasp eggs. Moreover, the development of surplus wasp larvae was siblicidal in earlier instars and nonsiblicidal gregarious one in the penultimate and last “sixth” instars. It is suggested that the optimal way for M. rufiventris to deal with high quality hosts (early instars) is to lay a single egg, while the optimal way to deal with low quality hosts (late instars) might be to superparasitize these hosts.     

Growth and development of the endoparasitic wasp Apanteles congregatus: dependence on host nutritional status and parasite load

ABSTRACT. Previously we have shown that the number of Apanteles congregatus Say (Hymenoptera, Braconidae) larvae developing in Manduca sexta (L.) (Lepidoptera, Sphingidae) larvae that are parasitized in the first instar determines the timing of emergence of the parasites from the host. Here we show that the first larval ecdysis of the wasps occurs after the host ecdyses to the terminal stage, regardless of whether that stage is the host's fourth, fifth or supernumerary sixth instar. Starvation of newly ecdysed terminal stage host larvae prevents emergence of the parasites. When starvation is begun at progressively later times, then an increasing proportion of the hosts have parasites that emerge, suggesting a period of indispensable host nutrition exists during which the host must feed to satisfy the developmental requirements of the parasites. In hosts fed ad libitum , the weight of the host plus its parasites at the time of emergence is positively correlated with the number of parasites developing in the host. When the weight of the parasites alone is subtracted from the weight of the host—parasite complex, the data show that heavily parasitized hosts have a larger host mass than lightly parasitized larvae. In contrast, the wasp larvae, and the adult males and females that develop from them, have lower individual weights after development in heavily parasitized hosts.     

大螟中肠氨肽酶N基因的克隆及表达谱分析

昆虫中肠氨肽酶N是Bt毒素的重要受体之一, 与Bt毒素的杀虫机制及昆虫Bt抗性的产生密切相关。本研究通过简并引物PCR结合RACE技术克隆并获得大螟 Sesamia inferens Bt受体蛋白--氨肽酶N （aminopeptidase N, APN）基因的cDNA序列全长, 经NCBI同源比对分析, 认为该基因为APN3基因, 并将其命名为SiAPN3（GenBank登录号为HQ636624）。序列分析表明, 该基因的cDNA序列全长为3 411 bp, 开放阅读框为3 018 bp, 编码1 006个氨基酸; 预测蛋白质分子量为114 kD, 等电点为4.95; 其推导的氨基酸序列中具有鳞翅目昆虫氨肽酶N典型的结构特征, 即含有1个N-和12个O-连接的糖基化位点, N-末端具有18个氨基酸的剪切信号肽, 谷氨酸锌化氨肽酶保守结构GAMEN, 锌结合位点HEXXHX18E, C-末端具有22个氨基酸的糖基磷脂酰肌醇(GPI)锚信号肽。采用实时定量PCR研究了SiAPN3在大螟4龄幼虫肠道不同部位和幼虫不同龄期的转录表达谱。结果表明, 该基因在幼虫中肠中的表达量最高, 其次为后肠, 前肠中表达量最低, 且中肠和后肠中的表达量显著高于前肠（P＜0.05）; SiAPN3在3龄幼虫中的表达量最高, 1龄幼虫中最低, 虽然3、 4日龄之间的表达量没有显著差异, 但二者均显著高于其他日龄, 1, 2和5日龄之间不存在显著差异（P>0.05）。该研究为阐明APN基因的功能及大螟对Bt抗性产生的分子机制奠定了基础。     

Mode of action of the venom of the ectoparasitic wasp,Euplectrus comstockii, in causing developmental arrest in the European corn borer,Ostrinia nubilalis

Euplectrus comstockii Howard (Hymenoptera: Eulophidae), is an ectoparasitic, gregarious wasp which parasitizes the larval stage of several important lepidopteran pests. Parasitization of both natural and unnatural hosts prevents molting in the parasitized instar. Here we report the effect of wasp venom on the European corn borer (unnatural host), an important pest of corn and other vegetables. Venom collected from venom glands of adultE. comstockii, when injected intoO. nubilalis 5th instars, inhibited the growth rate, development and molting of the injected larvae. The observed effect on molting was dose and age dependent. When 3rd, 4th and 5th instarO. nubilalis were envenomated by adult wasps, the larvae also were developmentally arrested and failed to undergo a molt. However, 3rd and 4th instars underwent apolysis (separation of the epidermis from the old cuticle) and produced new cuticle. Fifth instars did not. A premolt hemolymph ecdysteroid peak was not observed in these experimental 5th instars, but injections of 20-hydroxy-ecdysone induced apolysis and new cuticle formation. Envenomated 4th instars (on becoming pharate 5th instars) exhibited a premolt hemolymph ecdysteroid peak. HPLC/RIA revealed that 20-hydroxyecdysone was present in the hemolymph of these pharate 5th instars. Thus, in the European corn borer, the mode of action of the venom depended upon the instar parasitized. Our results support the presence of a venom component(s) that, in 4th instar hosts, inhibited ecdysis, but did not prevent hemolymph ecdysteroid levels from increasing sufficiently to stimulate apolysis. In 5th instars, the same, or perhaps, a different component(s) ofE. comstockii venom prevented the synthesis/release of ecdysteroid by inhibiting a previously unknown molt-regulating physiological event that occurs between days 3 and 4 of the instar. Deceased     

Developmental interaction between suboptimal instars of Spodoptera littoralis (Lepidoptera:Noctuidae) and its parasitoid Microplitis rufiventris (Hymenoptera:Braconidae)

Relative effects of parasitism by Microplitis rufiventris on the development of the third instar Spodoptera littoralis (preferable, optimal host) with the development of penultimate (5th) and last (6th) instars (suboptimal hosts) were investigated. Newly molted 6th instar hosts were more acceptable for parasitization by the wasp female than older hosts. In singly parasitized 3rd instar hosts, 82.0 +/- 3.9% of the parasitoid eggs developed to full-grown instar wasp larvae. However, parasitoid eggs deposited singly in 73.9 +/- 3.3% of 5th and 100% of 6th instar hosts failed to develop. Superparasitization in the 3rd instar hosts reduced the production of pseudoparasitized larvae and, conversely, all parasitized hosts yielded viable parasitoid offspring. In suboptimal hosts, the development interaction between the parasitoid and its host larvae was highly influenced by the age of hosts at parasitism, load of deposited eggs, and other parasitoid factors. The latter factors, e.g., mainly calyx fluid particles, might be involved in establishing parasitoid eggs in the suboptimal hosts. In the last two host instars, superparasitization significantly increased the number of parasitoid larvae successfully reaching their final instar. Variation in host quality, e.g., physiological status, might be attributed, in part, to the partial breakdown of the solitary habit observed in the earlier instars. More parasitoid eggs developed to mature parasitoid larvae in hosts superparasitized as 6th instar than parasitoid eggs laid in 5th instar hosts. Superparasitization significantly lengthened the developmental period of 5th and 6th host instars and inhibited their development to the pupal stage. Studying parasitoid development in suboptimal instars of its habitual host provided physiological insight, as shown here. The results may have implication for biological control and in vitro mass rearing programs with solitary parasitoids.     

Direct and indirect effects of predatory wasps (Polistes sp.: Vespidae) on gregarious caterpillars (Hemileuca lucina: Saturniidae)

Summary We examined how predation by vespid wasps,Polistes dominulus andP. fuscatus, affected the behavior, growth rate and survivorship of aggregated caterpillars ofHemileuca lucina (Saturniidae). Although these larvae can exhibit a variety of defense and escape behaviors, in general larvae reacted to wasp attacks by clinging to the hostplant. Neighboring larvae in the aggregation responded by leaving the feeding site and moving to the interior or base of the plant. To determine wheter wasp attack affected the behavior and growth of the caterpillars that escaped, a field experiment was conducted with treatments of: 1) larvae exposed to wasps, 2) larvae protected from wasps, and 3) larvae protected from wasps but with the attack of wasps simulated (=harassment). Over just one instar, protected larvae gained significantly more weight than the harassed larvae, which in turn weighed significantly more than the larvae that escaped the wasps. The behavior of attacked and harassed larvae differed from that of the protected larvae; the disturbed larvae often fed in smaller groups and in shaded portions of the plant where only mature leaves were available. A laboratory experiment showed that at 35° C (daytime temperature) larvae had significantly higher relative growth rates and significantly shorter instar duration than larvae reared at 25° C. Our results suggest that wasps, in addition to killing caterpillars, indirectly affect larval fitness by slowing larval growth, at least in part by forcing larvae into cooler microhabitats where leaves are of lower quality.     

Performance of Microplitis tuberculifer (Hymenoptera: Braconidae) parasitizing Mythimna separata (Lepidoptera: Noctuidae) in different larval instars

The solitary parasitoid Microplitis tuberculifer (Wesmael) is an important biological control agent of various lepidopteran pests in Asia. We examined the preference of M. tuberculifer for different instars of its common host, Mythimna separata (Walker), host instar effects on parasitoid development, and the consequences of parasitism in different stages for growth and consumption of host larvae. The wasp successfully parasitized the first four larval instars of M. separata, but not the fifth, which appeared to be behaviorally resistant. First and second instars were parasitized at higher rates compared to thirds and fourths in no-choice situations, ostensibly due to longer handling times for the latter, but second instars were most preferred in a choice test that presented all stages simultaneously. Although later instar hosts yielded heavier cocoons, the fastest parasitoid development was obtained in second instars. Lower sex ratios were obtained from first instars as females appeared to lay a smaller proportion of fertilized eggs in small hosts. Both weight gain and food consumption of parasitized larvae were reduced significantly within 24 h of parasitism, regardless of the stage parasitized, and final body weights were less than 10% those of unparasitized larvae. Thus, M. tuberculifer has good potential as a biological control agent of M. separata, successfully parasitizing the first four larval instars and dramatically reducing plant consumption by the host in all cases.     

Role of gregarine parasite Ascogregarina culicis (Apicomplexa: Lecudinidae) in the maintenance of Chikungunya virus in vector mosquito

Ascogregarina culicis and Ascogregarina taiwanensis are common gregarine parasites of Aedes aegypti and Aedes albopictus mosquitoes, respectively. These mosquito species are also known to transmit dengue and Chikungunya viruses. The sporozoites of these parasites invade the midgut epithelial cells and develop intracellularly and extracellularly in the gut to complete their life cycles. The midgut is also the primary site for virus replication in the vector mosquitoes. Therefore, studies were carried out with a view to determine the possible role of these gregarines in the vertical transmission of dengue and Chikungunya viruses from larval to adult stage. Experiments were performed by exposing first instar mosquito larvae to suspensions containing parasite oocysts and viruses. Since Ascogregarina sporozoites invade the midgut of first instar larvae, the vertical transmission was determined by feeding the uninfected first instar larvae on the freshly prepared homogenates from mosquitoes, which were dually infected with viruses and the parasite oocysts. Similarly, the role of protozoan parasites in the vertical transmission of viruses was determined by exposing fresh first instar larvae to the dried pellets of homogenates prepared from the mosquitoes dually infected with viruses and the parasite oocysts. Direct vertical transmission and the vertical transmission of CHIK virus through the oocyst of the parasites were observed in the case of Ae. aegypti mosquitoes. It is suggested that As. culicis may have an important role in the maintenance of CHIK virus during the inter-epidemic period.     

Molecular analysis of parasitoid linkages (MAPL): gut contents of adult parasitoid wasps reveal larval host

Metamorphosing insects often have complex and poorly known life histories. In particular, what they feed on during their larval stages remains unknown for the vast majority of species, and its documentation only results from difficult and time-intensive field observations, rearing or dissections. Through the application of a DNA analysis of gut contents in adult parasitoid wasps, we were able to selectively sequence a diagnostic DNA marker that permitted the identification of the host used by these wasps during their larval stages. By reproducing these results in species with different life histories, we excluded other potential sources of host DNA, confirming that after ingestion by the parasitoid larva the host DNA can persist through metamorphosis in the abdominal contents of the adult wasp. Our discovery considerably extends the applicability of molecular analysis of gut contents by enabling the documentation of food used by insects during their larval stages and thus increasing the accuracy and precision of food web studies. The 24% success rate of our approach is surprisingly high considering the challenging context for host DNA preservation, and we discuss the factors possibly affecting this rate. We propose molecular analysis of parasitoid linkages (MAPL) as a new method to document host-parasitoid associations at a faster pace and with unrivalled precision. Because of the key regulatory role of parasitoid wasps in ecosystems, which makes them the most commonly used biological control agents, MAPL will have immediate applications in both basic and applied biological sciences.