CRISPR/Cas9-mediated mutagenesis of the white gene in an ectoparasitic wasp, Habrobracon hebetor

BACKGROUND

The ectoparasitic wasp Habrobracon hebetor (Hymenoptera, Braconidae) can parasitize various species of lepidopteran pests. To maximize its potential for biological control, it is necessary to investigate its gene function through genome engineering.

RESULTS

To test the effectiveness of genome engineering system in H. hebetor, we injected the mixture of clustered regularly interspaced short palindromic repeats (CRISPR) -associated (Cas) 9 protein and single guide RNA(s) targeting gene white into embryos. The resulting mutants display a phenotype of eye pigment loss. The phenotype was caused by small indel and is heritable. Then, we compared some biological parameters between wildtype and mutant, and found there were no significant differences in other parameters except for the offspring female rate and adult longevity. In addition, cocoons could be used to extract genomic DNA for genotype during the gene editing process without causing unnecessary harm to H. hebetor.

CONCLUSION

Our results demonstrate that the CRISPR/Cas9 system can be used for H. hebetor genome editing and it does not adversely affect biological parameters of the parasitoid wasps. We also provide a feasible non-invasive genotype detection method using genomic DNA extracted from cocoons. Our study introduces a novel tool and method for studying gene function in H. hebetor, and may contribute to better application of H. hebetor in biocontrol. © 2023 Society of Chemical Industry.

First record of Tamarixiadahlsteni Zuparko (Hymenoptera, Eulophidae), a parasitoid of Triozaeugeniae Froggatt (Hemiptera, Triozidae) and current status of the Tamarixia species in Mexico

Parasitic wasps of the genus Tamarixia represent important biological control agents of members of the true bug group, Psylloidea, and are host specific; therefore, they can be used to control insect pests. In this study we report, for the first time, the presence of the parasitoid Tamarixiadahlsteni in Mexico and its mitochondrial barcode region of the cytochrome oxidase I gene (COI). We also review the species diversity of the genus Tamarixia in Mexico.

Novel gene rearrangement in the complete mitochondrial genome of Telenomus remus (Hymenoptera: Scelionidae)

The current study describes the complete mitochondrial genome (mitogenome) of an egg parasitoid wasp, Telenomus remus Nixon 1937. This mitogenome is 16,014 bp in length, consisting of 37 typical coding genes (13 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes). The start codons of the protein-coding genes are ATN and the stop codons are TAA or TAG. The secondary structures of most transfer RNA genes could be detected, except for trnS(AGN) and trnQ. Rearrangements of 14 transfer RNA genes in the mitogenome has generated a novel gene order, including two new gene clusters, trnN-trnF-trnS(AGN)-trnR between ND3 and ND5, and trnM-trnV-CR-trnE-trnC-trnY-trnQ-trnI-trnA between srRNA and ND2. The sister relationship between T. remus and other congeneric species is highly supported by phylogenetic analysis based on the protein-coding and ribosomal RNA gene sequences.

Insecticide-contaminated honeydew: risks for beneficial insects

Honeydew is the sugar-rich excretion of phloem-feeding hemipteran insects such as aphids, mealybugs, whiteflies, and psyllids, and can be a main carbohydrate source for beneficial insects in some ecosystems. Recent research has revealed that water-soluble, systemic insecticides contaminate honeydew excreted by hemipterans that feed on plants treated with these insecticides. This contaminated honeydew can be toxic to beneficial insects, such as pollinators, parasitic wasps and generalist predators that feed on it. This route of exposure has now been demonstrated in three plant species, for five systemic insecticides and four hemipteran species; therefore, we expect this route to be widely available in some ecosystems. In this perspective paper, we highlight the importance of this route of exposure by exploring: (i) potential pathways through which honeydew might be contaminated with insecticides; (ii) hemipteran families that are more likely to excrete contaminated honeydew; and (iii) systemic insecticides with different modes of action that might contaminate honeydew through the plant. Furthermore, we analyse several model scenarios in Europe and/or the USA where contaminated honeydew could be problematic for beneficial organisms that feed on this ubiquitous carbohydrate source. Finally, we explain why this route of exposure might be important when exotic, invasive, honeydew-producing species are treated with systemic insecticides. Overall, this review opens a new area of research in the field of ecotoxicology to understand how insecticides can reach non-target beneficial insects. In addition, we aim to shed light on potential undescribed causes of insect declines in ecosystems where honeydew is an important carbohydrate source for insects, and advocate for this route of exposure to be included in future environmental risk assessments.

Two new species of the family Megalyridae (Hymenoptera) from China

Two new species of the small and rarely collected family Megalyridae are described from China: Carminatordaliensis Chen & Liuhe, sp. nov. from Yunnan and Ettchellsiahainanensis Chen & Liuhe, sp. nov. from Hainan. A key to megalyrid species of China is provided. The biogeographical implication of the new taxa is discussed.

Effects of sugar sources on adult longevity, survival and related gene expression in an endoparasitoid, Pteromalus puparum (Hymenoptera: Pteromalidae)

BACKGROUND

Adult parasitic wasps take sugars to meet their energy needs and display different lifespans and fertility in response to different sugar sources. Pteromalus puparum is an endoparasitoid with a wide range of hosts, including many lepidopteran pests. As a potential natural enemy resource, the availability of sugar sources has profound effects for wasp applications and host populations dynamics.

RESULTS

We assessed the effect of feeding sucrose and honey on the lifespan of P. puparum in the range 0-40% (w/v). The results indicated a statistically significant positive effect of sucrose and honey solutions on the lifespan of P. puparum female adults. Correlation analyses confirmed a strong positive correlation between high concentrations of sugar and extended lifespan. The optimum concentration of sucrose solution for wasps was 20%, while 10% for honey. Then, we examined the expression patterns of 15 lifespan-related genes. The results showed that the relative expression levels of 14 genes were significantly correlated with the mean lifespan of sucrose-fed wasps, and six genes correlated with the mean lifespan of honey-fed wasps. In addition, the models for lifespan prediction were constructed.

CONCLUSION

We elaborated the quantitative effects of two sugar sources (sucrose and honey) on P. puparum lifespan, investigated the expression patterns of lifespan-related genes when fed different sugar sources, and developed round lifespan prediction models accordingly. This study provides a novel tool for studying the longevity regulating mechanisms of parasitic wasps, and may be instructive for mass-production of parasitoids as biological control agents. © 2020 Society of Chemical Industry.

Evaluation of Sensitivity to Phoxim and Cypermethrin in an Endoparasitoid, Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae), and Its Parasitization Efficiency Under Insecticide Stress

Insecticides can have consequences for beneficial arthropods. Insect parasitoids can contact insecticides through direct exposure spray droplets or residues on crop foliage. Here, we focus on better understand the response of Meteorus pulchricornis (Wesmael), a parasitoid wasp of lepidopteran pests, and its detoxification mechanisms on stress caused by phoxim and cypermethrin. Hence, we determined the dose-mortality curves and estimating the sublethal concentrations (LC30 and LC50). Then, we applied the sublethal concentrations against adult parasitoids to assess its survival, parasitism efficacy, and also developmental and morphometric parameters of their offspring. Simultaneously, we check the activities of glutathione S-transferase (GST), acetylcholinesterase (AChE), and peroxidase (POD) after sublethal exposure of both insecticides, which has measured until 48 h after treatment. Overall, phoxim and cypermethrin exhibited acute lethal activity toward the parasitoid with LC50 values 4.608 and 8.570 mg/liter, respectively. Also, we detect that LC30 was able to trigger the enzymatic activity of GST, AChE, and POD, suggesting a potential detoxification mechanism. However, even when subjected to sublethal exposure, our results indicate strong negatives effects, in particular for phoxim, which has affected the parasitism efficacy and also the developmental and morphometric parameters of M. pulchricornis offspring. Therefore, it can be concluded that both phoxim and cypermethrin have negative impacts on M. pulchricornis and we suggest cautioning their use and the need for semifield and field assessments to confirm such an impact.

Response of Trichogramma spp. (Hymenoptera: Trichogrammatidae) to Insecticides at Concentrations Sublethal to Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)

Trichogramma japonicum Ashmead (Hymenoptera: Trichogrammatidae) and Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) are important parasitoids of Lepidopteran pests and are used for biological control in rice fields. In this study, the response of two of these parasitoids to four insecticides (chlorpyrifos, chlorantraniliprole, emamectin benzoate, and spinosad) were evaluated at target sublethal concentrations (TSC10 and TSC25, representing the LC10 and LC25 to the target pest) of the important rice pest, Cnaphalocrocis medinalis (Guenée). Each of the insecticides led to the mortality of adult T. japonicum and T. dendrolimi at TSC10 and TSC25, whereas no significant differences in the mortality of T. japonicum between TSC10 of chlorantraniliprole and control groups occurred. The parasitic capacity increased at F0 of T. japonicum at the two TSCs of spinosad treated host eggs, whereas the TSC10 was lower for emamectin benzoate at F1 for T. japonicum. The TSCs of chlorpyrifos treated host eggs negatively influenced the emergence rates of T. japonicum at F1. Emamectin benzoate with TSC10 reduced the female ratio of T. japonicum at F1. For T. dendrolimi, the TSCs of chlorpyrifos treated host eggs negatively influenced the emergence rates at F1. These findings indicate that T. japonicum and T. dendrolimi are affected by insecticides at TSCs, and among the four insecticides, chlorantraniliprole had the lowest mortality rates for T. japonicum and T. dendrolimi at TSCs.

Functional principles of steerable multi-element probes in insects

Hemipterans, mosquitoes, and parasitic wasps probe in a variety of substrates to find hosts for their larvae or food sources. Probes capable of sensing and precise steering enable insects to navigate through solid substrates without visual information and to reach targets that are hidden deep inside the substrate. The probes belong to non‐related taxa and originate from abdominal structures (wasps) or mouthparts (hemipterans and mosquitoes), but nevertheless share several morphological characteristics. Although the transport function clearly differs (egg laying and acquisition of liquid food), the functional demands on the mechanical behaviour of the probe within the substrate tend to be similar. The probe needs to be thin to limit substrate deformation, and long, in order to attain substantial path lengths or depths. We linked the morphology across taxa to the different functional requirements, to provide insights into the biology of probing insects and the evolution of their probes.

Current knowledge of insect probes is spread over many taxa, which offers the possibility to derive general characteristics of insect probing. Buckling during initial puncturing is limited by external support mechanisms. The probe itself consist of multiple (3–6) parts capable of sliding along one another. This multi‐part construction presumably enables advancement and precise three‐dimensional steering of the probe through the substrate with very low net external pushing forces, preventing buckling during substrate penetration. From a mechanical viewpoint, a minimum of three elements is required for 3D steering and volumetric exploration, as realised in the ovipositors of wasps. More elements, such as in six‐element probes of mosquitoes, may enhance friction in soft substrates. Alternatively, additional elements can have functions other than ‘drilling’, such as saliva injection in mosquitoes.

Despite the gross similarities, probes show differences in their cross sections, tip morphologies, relative lengths of their elements, and the shape of their interconnections. The hypothesis is that the probe morphology is influenced by the substrate properties, which are mostly unknown. Correlating the observed diversity to substrate‐specific functional demands is therefore currently impossible.

We conclude that a multipart probe with sliding elements is highly effective for volumetric substrate probing. Shared functional demands have led to an evolutionary convergence of slender multi‐element probes in disparate insect taxa. To fully understand 3D probing, it is necessary to study the sensory and material properties, as well as the detailed kinematics and dynamics of the various probes in relation to the nature of the selective pressure originating from the species‐specific substrates. Such knowledge will deepen our understanding of probing mechanisms and may support the development of slender, bio‐inspired probes.

Comparison of Molecular and Conventional Methods for Estimating Parasitism Level in the Pomegranate Aphid Aphis punicae (Hemiptera: Aphididae)

Aphidiinae (Braconidae: Aphidiinae) is a subfamily of endoparasitic wasps specialized in parasitizing aphids. Although, to date, different methods have been used to measure parasitism level, obtaining an accurate estimate remains challenging due to several limiting factors. This study was set to: 1) Compare efficiency of conventional and molecular-based methods in estimating parasitism level of the pomegranate aphid Aphis punicae (Passerini; Hemiptera: Aphididae), and 2) Estimate seasonal activity of the Aphidiinae parasitoids of the pomegranate aphid. The molecular approach (polymerase chain reaction [PCR]) detected the presence of three main parasitoids Lysiphlebus fabarum (Marshal; Hymenoptra: Braconidae), Binodoxys angelicae (Haliday; Hymenoptra: Braconidae), and Ephedrus persicae (Frogatt; Hymenoptra: Braconidae). The presence of hyperparasitoid and aphid DNAs did not interfere with the outcome, indicating specificity of the selected primers. Minimum concentrations of DNA needed for successful amplifications were 16.33, 28.65, and 22.65 ng µl⁻¹, for L. fabarum, B. angelicae, and E. persicae, respectively. The level of parasitism was significantly higher in spring (28.42%) than both summer and fall; parasitism level during summer (11.89%) and fall (5.86%) formed a homogeneous statistical subset. Although the overall level of parasitism estimated by PCR (22.7%) was more than twofold higher than those estimated by a conventional counting method (10.5%), there was a strong positive correlation between the two approaches. Provided the potential limitations of either method, simultaneous use of both methods was recommended for an objective estimate of the effectiveness of the Aphidiinae parasitoids as biological control agents of A. punicae.

Multiplex PCR in determination of Opiinae parasitoids of fruit flies, Bactrocera sp., infesting star fruit and guava

Malaysia is a tropical country that produces commercial fruits, including star fruits, Averrhoa carambola L. (Oxalidales: Oxalidaceae), and guavas, Psidium guajava L. (Myrtales: Myrtaceae). There is a high demand for these fruits, and they are planted for both local consumption and export purposes. Unfortunately, there has been a gradual reduction of these fruits, which has been shown to be related to fruit fly infestation, especially from the Bactrocera species. Most parasitic wasps (Hymenoptera: Braconidae: Opiinae) are known as parasitoids of fruit fly larvae. In this study, star fruits and guavas infested by fruit fry larvae were collected from the Malaysian Agricultural Research and Development Institute. The parasitized larvae were reared under laboratory conditions until the emergence of adult parasitoids. Multiplex PCR was performed to determine the braconid species using two mitochondrial DNA markers, namely cytochrome oxidase subunit I and cytochrome b. Two benefits of using multiplex PCR are the targeted bands can be amplified simultaneously using the same reaction and the identification process of the braconid species can be done accurately and rapidly. The species of fruit flies were confirmed using the COI marker. The results obtained from our study show that Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae), Fopius arisanus (Sonan), and Pysttalia incisi (Silvestri) were parasitoids associated with Bactrocera carambolae (Drew and Hancock) (Diptera: Tephritidae) infested star fruits. Fopius arisanus was also the parasitoid associated with Bactrocera papayae (Drew and Hancock) infested guavas. Maximum parsimony was been constructed in Opiinae species to compare tree resolution between these two genes in differentiating among closely related species. The confirmation of the relationship between braconids and fruit fly species is very important, recognized as preliminary data, and highly necessary in biological control programs.

A taxonomic study on the genus Ettchellsia Cameron, with descriptions of three new species (Hymenoptera, Megalyridae, Dinapsini)

Three new species of Ettchellsia Cameron, namely, Ettchellsia ignitasp. n. from Peninsular Malaysia and Borneo, Ettchellsia nigripessp. n. from Sulawesi and Ettchellsia reidisp. n. from Borneo are described and illustrated. A key to the species of Ettchellsia is provided based on females.

Sex determination meltdown upon biological control introduction of the parasitoid Cotesia rubecula?

Natural enemies may go through genetic bottlenecks during the process of biological control introductions. Such bottlenecks are expected to be particularly detrimental in parasitoid Hymenoptera that exhibit complementary sex determination (CSD). CSD is associated with a severe form of inbreeding depression because homozygosity at one or multiple sex loci leads to the production of diploid males that are typically unviable or sterile. We observed that diploid males occur at a relatively high rate (8–13% of diploid adults) in a field population of Cotesia rubecula in Minnesota, USA, where this parasitoid was introduced for biological control of the cabbage white Pieris rapae. However, our laboratory crosses suggest two-locus CSD in a native Dutch population of C. rubecula and moderately high diploid males survival (approximately 70%), a scenario expected to produce low proportions of diploid males. We also show that courtship behavior of diploid males is similar to that of haploid males, but females mated to diploid males produce only very few daughters that are triploid. We use our laboratory data to estimate sex allele diversity in the field population of C. rubecula and discuss the possibility of a sex determination meltdown from two-locus CSD to effective single-locus CSD during or after introduction.