Comparative Analysis of the Venom Proteins from Two Eupelmid Egg Parasitoids Anastatus japonicus and Mesocomys trabalae

Parasitic wasps are abundant and diverse Hymenoptera insects that lay their eggs inside or on the external surface of the host and inject venom into the host to create a more favorable environment for the larvae to survive and regulate the host's immunity, metabolism, and development. But research on the composition of egg parasitoid venom is very limited. In this study, we used a combination of transcriptomic and proteomic approaches to identify the protein fractions of the venom in both eupelmid egg parasitoids, Anastatus japonicus and Mesocomys trabalae. We identified 3422 up-regulated venom gland genes (UVGs) in M. trabalae and 3709 in A. japonicus and analyzed their functions comparatively. By proteome sequencing, we identified 956 potential venom proteins in the venom pouch of M. trabalae, of which 186 were contained in UVGs simultaneously. A total of 766 proteins were detected in the venom of A. japonicus, of which 128 venom proteins were highly expressed in the venom glands. At the same time, the functional analysis of these identified venom proteins was carried out separately. We found the venom proteins in M. trabalae are well known but not in A. japonicus, which may be related to the host range. In conclusion, identifying venom proteins in both egg parasitoid species provides a database for studying the function of egg parasitoid venom and its parasitic mechanism.

Two new host records for Centrodoraitalica Ferrière (Hymenoptera, Aphelinidae) from eggs of Tettigoniidae (Orthoptera, Ensifera) in northeastern Italy

The egg parasitoid Centrodoraitalica Ferrière is reported for the first time from sentinel eggs of two species of Tettigoniidae (Orthoptera), Pachytrachisgracilis (Brunner von Wattenwyl) and Eupholidopteraschmidti (Fieber). In Italy, only two hosts of this parasitic wasp are known, one of which is a tettigoniid species. Exposure of sentinel eggs represented a useful method to detect new host associations of this parasitoid species that can search for their host's eggs in the ground. The parasitoids were identified by comparing our specimens with those of the type series, and the original description of C.italica.

Functional Morphology of the Antennae and Sensilla of Coeloides qinlingensis Dang et Yang (Hymenoptera: Braconidae)

Coeloides qinlingensis Dang et Yang, 1989 (Hymenoptera: Braconidae) is a biocontrol agent of several scolytid pine pests in Southwest China. We examined the fine morphology of the antennae of adult C. qinlingensis, as well as the type, shape, and distribution of antennal sensilla, via scanning electron microscopy. The antennae of female and male C. qinlingensis are filiform and comprise a scape, pedicel, and 31-36 flagellomeres. We detected sexual dimorphism in antennal flagellar length but not in the length of other subsegments. A total of nine morphological types of antennal sensilla varying in cuticular pore structure are present in both sexes, including nonporous types (sensilla trichodea, sensilla chaetica (2 subtypes), and sensilla coeloconica); apical pore types (sensilla basiconica and sensilla auricillica); and multiporous types (dome-shaped sensilla and sensilla placodea (2 subtypes)). Dome-shaped sensilla and sensilla auricillica are reported for the first time for C. qinlingensis, and their shape differs from that of sensilla in other parasitic wasps. The functional morphology of the sensilla of C. qinlingensis was compared with that of the sensilla of other parasitic wasps, including those that parasitize concealed insects. This information provides a foundation for further research on the chemical communication and behavior of C. qinlingensis.

The biological significance of lipogenesis in Nasonia vitripennis

Parasitic wasps have long been thought to be unable to synthesize fatty acids de novo, but recent ¹³C-labelling studies have challenged this view. It remained unclear, however, whether the reported biosynthesis rates are of biological relevance. Here, we show in Nasonia vitripennis that ageing females with partly depleted lipid reserves produce biologically relevant amounts of fatty acids de novo. Females with varying oviposition history (0-48 h) prior to feeding 20% ¹³C-labelled glucose solution showed ¹³C-incorporation rates of (mean ± SEM) 30 ± 2%, 50 ± 2%, 49 ± 3% and 21 ± 2% in palmitic, stearic, oleic and linoleic acid, respectively. The absolute amounts of fatty acids synthesized de novo across treatments corresponded to 28 ± 3 egg lipid equivalents. Females incorporated de novo synthesized fatty acids into their eggs, and glucose-fed females laid more eggs than water-fed control females. The number of eggs laid prior to glucose feeding did not correlate with the degree of lipogenesis, but the amounts of de novo synthesized fatty acids correlated with constitutive (not synthesized de novo) fatty acids. Hence, glucose feeding has a twofold effect on the fatty acid status of N. vitripennis females by decelerating the catabolism of existing fat reserves and partially replenishing ebbing fat reserves by lipogenesis.

First report of Eutrichosomella Girault (Hymenoptera, Aphelinidae) from China, with description of a new species

The genus Eutrichosomella Girault is recorded for the first time from China (Yunnan Province), and Eutrichosomellayunnanensis sp. nov. (♀, ♂) is described and illustrated. A distribution map of this genus is presented.

The mitochondrial genome of parasitic wasp: Anisopteromalus calandrae (Howard, 1881) (Hymenoptera: Pteromalidae)

The parasitic wasp Anisopteromalus calandrae is a natural enemy of numbers store product pests. The mitochondrial genome (mitogenome) of A. calandrae was obtained by second-generation sequencing. The assembled mitogenome of A. calandrae is 15,954 bp long (GenBank accession: MW817149) and contains 37 typical animal mitochondrial genes. The order of the mitochondrial genes is identical to that of another species of Chalcidoidae (Pteromalus puparum). All protein-coding genes start with ATN codons, and end with TAA, except NAD4 and NAD5 with T.

Effects of Plant Stress on Aphid-Parasitoid Interactions: Drought Improves Aphid Suppression

Drought events have the potential to mediate tri-trophic interactions. Changes in plant quality influence herbivore performance, which affects prey availability and quality for natural enemies. Parasitoid wasps are particularly vulnerable to these changes since their development is inextricably linked to that of their prey. However, we know little about the indirect effects of plant water limitation on parasitoid performance, especially the consequences of mild water limitation. This study investigated the ability of a parasitoid wasp (Aphidius colemani Viereck (Hymenoptera: Braconidae)) to suppress aphid (Rhopalosiphum padi L. (Hemiptera: Aphididae)) populations on well-watered, mildly stressed, or highly stressed wheat (Triticum aestivum L. (Poales: Poaceae)). We then investigated the role that aphid body size and behavioral interactions might play in wasp acceptance of aphid hosts. We found improved aphid suppression under mild and high-water limitation, but the underlying mechanisms were different. Mild-stress appeared to maximize parasitoid performance, as indicated by the highest mummy production. Aphids were larger when feeding on mildly stressed plants than on any other treatment, which suggests improved aphid quality for parasitoids. Improved aphid suppression under high-stress may have been driven by enhanced nonconsumptive effects. Despite improved aphid suppression, mummy formation was lowest on highly stressed plants. High-stress conditions have been shown to negatively affect aphid performance, so improved aphid suppression may be driven by poor aphid performance exacerbating the cost of interactions with parasitoids, such as stinging. No differences were observed in parasitoid foraging behaviors such as antennation or stinging across any treatments. This study highlights the importance of plant water stress intensity in affecting outcomes of parasitoid-host interactions.

Parasitic wasps do not lack lipogenesis

Fatty acids are crucial primary metabolites for virtually all creatures on earth. Most organisms thus do not rely exclusively on a nutritional supply containing fatty acids, but have the ability to synthesize fatty acids and triacylglycerides de novo from carbohydrates in a process called lipogenesis. The ubiquity of lipogenesis has been questioned by a series of studies reporting that many parasitic wasps (parasitoids) do not accumulate lipid mass despite having unlimited access to sugar. This has been interpreted as an evolutionary metabolic trait loss in parasitoids. Here, we demonstrate de novo biosynthesis of fatty acids from 13C-labelled α-d-glucose in 13 species of parasitoids from seven families. We furthermore show in the model organism Nasonia vitripennis that lipogenesis occurs even when lipid reserves are still intact, but relative 13C-incorporation rates increase in females with widely depleted fat reserves. We therefore conclude that the presumed 'lack of lipogenesis' in parasitoids needs to be re-evaluated.

Multi-camera field monitoring reveals costs of learning for parasitoid foraging behaviour

Dynamic conditions in nature have led to the evolution of behavioural traits that allow animals to use information on local circumstances and adjust their behaviour accordingly, for example through learning. Although learning can improve foraging efficiency, the learned information can become unreliable as the environment continues to change. This could lead to potential fitness costs when memories holding such unreliable information persist. Indeed, persistent unreliable memory was found to reduce the foraging efficiency of the parasitoid Cotesia glomerata under laboratory conditions.

Here, we evaluated the effect of such persistent unreliable memory on the foraging behaviour of C. glomerata in the field. This is a critical step in studies of foraging theory, since animal behaviour evolved under the complex conditions present in nature.

Existing methods provide little detail on how parasitoids interact with their environment in the field, therefore we developed a novel multi‐camera system that allowed us to trace parasitoid foraging behaviour in detail. With this multi‐camera system, we studied how persistent unreliable memory affected the foraging behaviour of C. glomerata when these memories led parasitoids to plants infested with non‐host caterpillars in a semi‐field set‐up.

Our results demonstrate that persistent unreliable memory can lead to maladaptive foraging behaviour in C. glomerata under field conditions and increased the likelihood of oviposition in the non‐host caterpillar Mamestra brassica. Furthermore, these time‐ and egg‐related costs can be context dependent, since they rely on the plant species used.

These results provide us with new insight on how animals use previously obtained information in naturally complex and dynamic foraging situations and confirm that costs and benefits of learning depend on the environment animals forage in. Although behavioural studies of small animals in natural habitats remain challenging, novel methods such as our multi‐camera system contribute to understanding the nuances of animal foraging behaviour.

Two new species of Paraphytis (Hymenoptera, Aphelinidae) from Southwest China

Two new species of Paraphytis Compere, P.bannaensissp. nov. and P.pseudovittatussp. nov., are described from the Xishuangbanna Rainforest (Southwest China). A key to species from China based on females is provided.

Bracon brevicornis Genome Showcases the Potential of Linked-Read Sequencing in Identifying a Putative Complementary Sex Determiner Gene

Bracon brevicornis is an ectoparasitoid of a wide range of larval-stage Lepidopterans, including several pests of important crops, such as the corn borer, Ostrinia nubilalis. It is also one of the earliest documented cases of complementary sex determination in Hymenoptera. Here, we present the linked-read-based genome of B. brevicornis, complete with an ab initio-derived annotation and protein comparisons with fellow braconids, Fopius arisanus and Diachasma alloeum. We demonstrate the potential of linked-read assemblies in exploring regions of heterozygosity and search for structural and homology-derived evidence of the complementary sex determiner gene (csd).

Identification of Neuropeptides and Their Receptors in the Ectoparasitoid, Habrobracon hebetor

Neuropeptides are a group of signal molecules that regulate many physiological and behavioral processes by binding to corresponding receptors, most of which are G-protein-coupled receptors (GPCRs). Using bioinformatic methods, we screened genomic and transcriptomic data of the ectoparasitoid wasp, Habrobracon hebetor, and annotated 34 neuropeptide candidate precursor genes and 44 neuropeptide receptor candidate genes. The candidate neuropeptide genes were found to encode all known insect neuropeptides except allatotropin, neuropeptide F, pigment dispersing factor, and CCHamides. When compared with the endoparasitic wasp Pteromalus puparum and the ectoparasitic wasp Nasonia vitripennis, trissin and FMRFamide were found only in H. hebetor. A similar result held for the neuropeptide receptor genes, for the receptors were found in H. hebetor except the receptors of CCHamides and neuroparsin. Furthermore, we compared and analyzed the differences in neuropeptides in eight Braconidae wasps and identified natalisin in H. hebetor, Diachasma alloeum, Fopius arisanus and Microplitis demolitor, but not in the other wasps. We also analyzed the transcriptome data and qRT-PCR data from different developmental stages and tissues to reveal the expression patterns of the neuropeptides and their receptors. In this study, we revealed composition of neuropeptides and neuropeptide receptors in H. hebetor, which may contribute to future neurobiological studies.

Tripartite Interactions among Ixodiphagus hookeri, Ixodes ricinus and Deer: Differential Interference with Transmission Cycles of Tick-Borne Pathogens

For the development of sustainable control of tick-borne diseases, insight is needed in biological factors that affect tick populations. Here, the ecological interactions among Ixodiphagus hookeri, Ixodes ricinus, and two vertebrate species groups were investigated in relation to their effects on tick-borne disease risk. In 1129 questing ticks, I. hookeri DNA was detected more often in I. ricinus nymphs (4.4%) than in larvae (0.5%) and not in adults. Therefore, we determined the infestation rate of I. hookeri in nymphs from 19 forest sites, where vertebrate, tick, and tick-borne pathogen communities had been previously quantified. We found higher than expected co-occurrence rates of I. hookeri with deer-associated Anaplasma phagocytophilum, and lower than expected rates with rodent-associated Borrelia afzelii and Neoehrlichia mikurensis. The prevalence of I. hookeri in nymphs varied between 0% and 16% and was positively correlated with the encounter probability of ungulates and the densities of all life stages of I. ricinus. Lastly, we investigated the emergence of I. hookeri from artificially fed, field-collected nymphs. Adult wasps emerged from seven of the 172 fed nymphs. From these observations, we inferred that I. hookeri is parasitizing I. ricinus larvae that are feeding on deer, rather than on rodents or in the vegetation. Since I. hookeri populations depend on deer abundance, the main propagation host of I. ricinus, these wasps have no apparent effect on tick populations. The presence of I. hookeri may directly interfere with the transmission cycle of A. phagocytophilum, but not with that of B. afzelii or N. mikurensis.

Insects and incest: Sib-mating tolerance in natural populations of a parasitoid wasp

Sib-mating avoidance is a pervasive behaviour that is expected to evolve in species subject to inbreeding depression. Although laboratory studies provide elegant demonstrations, small-scaled bioassays minimize the costs of mate finding and choice, and thus may produce spurious findings. We therefore combined laboratory experiments with field observations to examine the existence of inbreeding avoidance using the parasitoid wasp Venturia canescens. In the laboratory, our approach consisted of mate-choice experiments to assess kin discrimination in population cages with competitive interactions. A higher mating probability after sib rejections suggested that females could discriminate their sibs; however, in contrast to previous findings, sib-mating avoidance was not observed. To compare our laboratory results to field data, we captured 241 individuals from two populations. Females laid eggs in the lab, and 226 daughters were obtained. All individuals were genotyped at 18 microsatellite loci, which allowed inference of the genotype of each female's mate and subsequently the relatedness within each mating pair. We found that the observed rate of sib-mating did not differ from the probability that sibs encountered one another at random in the field, which is consistent with an absence of sib-mating avoidance. In addition, we detected a weak but significant male-biased dispersal, which could reduce encounters between sibs. We also found weak fitness costs associated with sib-mating. As such, the sex-biased dispersal that we found is probably sufficient to mitigate these costs. These results imply that kin discrimination has probably evolved for purposes other than mate choice, such as superparasitism avoidance.

Anastatus Motschulsky (Hymenoptera, Eupelmidae): egg parasitoids of Caligula japonica Moore (Lepidoptera, Saturniidae) in China

Four species of Anastatus Motschulsky (Hymenoptera, Eupelmidae, Eupelminae) are newly reported as egg parasitoids of the Japanese giant silkworm, Caligulajaponica Moore and, as an alternate laboratory host, the Chinese oak silk moth, Antheraeapernyi (Guérin-Méneville) (Lepidoptera, Saturniidae) in China. The four species, A.fulloi Sheng & Wang, 1997, A.gansuensis Chen & Zang, sp. nov., A.japonicus Ashmead, 1904, and A.meilingensis Sheng, 1998, were reared initially from eggs of C.japonica collected in Gansu, Jilin and Liaoning provinces and subsequently cultured in the laboratory on eggs of A.pernyi. An illustrated key to differentiate females of the four species, and males of some of the species is provided. Key features are illustrated, both sexes of the new species are described, and diagnoses of females of the other species are given.

First record of the genus Oodera Westwood, 1874 (Hymenoptera, Pteromalidae, Cleonyminae, Ooderini) from the Arabian Peninsula, with the description of four new species

The genus Oodera Westwood, 1874 (Hymenoptera, Pteromalidae, Cleonyminae) is recorded for the first time for the Arabian Peninsula, from the Kingdom of Saudi Arabia and the Sultanate of Oman. The present study is based on specimens reared from xylophagous beetle larvae of the family Buprestidae (Coleoptera) infesting dead Acacia trees from Al-Dakhiliyah and Dhofar governorates in Oman and Al-Baha, Asir and Riyadh regions in Saudi Arabia. Four new species, Oodera arabica sp. nov., O. omanensis sp. nov., O. rapuzzii sp. nov., and O. similis sp. nov. are described, illustrated and compared with closely related Oodera species. An illustrated key and the xylophagous host records of the species are also provided.

Growth and Fatty Acid Metabolism of Aphis gossypii Parasitized by the Parasitic Wasp Lysiphlebia japonica

Parasitism usually causes considerable changes in lipids and fatty acids by redirecting the development of the host. In this study, changes in weight and in free fatty acid content of cotton aphids were recorded after aphids had been parasitized. Results showed that the weight of parasitized Aphis gossypii was increased compared to nonparasitized aphids, and significantly increased weights were detected at 1, 2, and 3 instars after parasitization by Lysiphlebia japonica. Free fatty acid test kits and GC-MS showed that the fatty acid content increased in the early stage of parasitization but decreased after 3 days of parasitization. Seven genes related to the fatty acid synthesis pathway were significantly upregulated in the parasitized aphids, where they were 1.96-10.97 times greater. Our data described the change that occurs in the fatty acid content of parasitized A. gossypii.

No gains for bigger brains: Functional and neuroanatomical consequences of relative brain size in a parasitic wasp

Heritable genetic variation in relative brain size can underlie the relationship between brain performance and the relative size of the brain. We used bidirectional artificial selection to study the consequences of genetic variation in relative brain size on brain morphology, cognition and longevity in Nasonia vitripennis parasitoid wasps. Our results show a robust change in relative brain size after 26 generations of selection and six generations of relaxation. Total average neuropil volume of the brain was 16% larger in wasps selected for relatively large brains than in wasps selected for relatively small brains, whereas the body length of the large‐brained wasps was smaller. Furthermore, the relative volume of the antennal lobes was larger in wasps with relatively large brains. Relative brain size did not influence olfactory memory retention, whereas wasps that were selected for larger relative brain size had a shorter longevity, which was even further reduced after a learning experience. These effects of genetic variation on neuropil composition and memory retention are different from previously described effects of phenotypic plasticity in absolute brain size. In conclusion, having relatively large brains may be costly for N. vitripennis, whereas no cognitive benefits were recorded.

Review of Dotocryptus Brèthes (Hymenoptera, Ichneumonidae, Cryptinae), with a New Species from Colombia

The taxonomic limits of the Neotropical genus Dotocryptus Brèthes are reviewed. The genus is characterized mainly by the very long ovipositor, at least 2.2× as long as hind tibia; apex of ovipositor distinctly depressed, ventral valve expanded, and overlapping dorsal valve as a sheath; and mandible long with ventral tooth longer than dorsal one. A new species, Dotocryptus arcadius sp. nov., from Colombia is described and illustrated. The new species can be diagnosed mainly by the head and mesosoma with multiple whitish marks; epicnemial carina reaching 0.2-0.3 of distance to subalar ridge; legs marked with dark brown, orange, and whitish; and metasoma polished and glabrate. This is the northernmost record of the genus, previously known from Ecuador to southern Chile. An updated identification key to the species of the genus is provided, as well as diagnoses and new records for the previously known species.

Habitat or temporal isolation: Unraveling herbivore-parasitoid speciation patterns using double digest RADseq

Ecological speciation is often observed in phytophagous insects and their parasitoids due to divergent selection caused by host-associated or temporal differences. Most previous studies have utilized limited genetic markers or distantly related species to look for reproductive barriers of speciation. In our study, we focus on closely related species of Lygus bugs and two sister species of Peristenus parasitoid wasps. Using mitochondrial DNA COI and genomewide SNPs generated using ddRADseq, we tested for potential effects of host-associated differentiation (HAD) or temporal isolation in this system. While three species of Lygus are clearly delineated with both COI and SNPs, no evidence of HAD or temporal differentiation was detected. Two Peristenus sister species were supported by both sets of markers and separated temporally, with P. mellipes emerging early in June and attacking the first generation of Lygus, while P. howardi emerging later in August and attacking the second generation of their hosts. This is one of the few studies to examine closely related hosts and parasitoids to examine drivers of diversification. Given the results of this study, the Lygus-Peristenus system demonstrates temporal isolation as a potential barrier to reproductive isolation for parasitoids, which could indicate higher parasitoid diversity in regions of multivoltine hosts. This study also demonstrates that incorporating systematics improves studies of parasitoid speciation, particularly by obtaining accurate host records through rearing, carefully delimiting cryptic species and examining population-level differences with genomic-scale data among closely related taxa.

Previous Interspecific Courtship Impairs Female Receptivity to Conspecifics in the Parasitoid Wasp Nasonia longicornis But Not in N. vitripennis

Interspecific sexual interactions are not uncommon in animals. In sympatry, females often face the risk of accidentally mating with a heterospecific male. Based on the actual risks imposed by the environment at a given time and place, females should be able to adjust their mate acceptance in order to avoid interspecific copulations as well as accidentally refusing to mate with a conspecific. We investigate the ability of females of the two parasitoid wasp species Nasonia vitripennis (Nv) and N. longicornis (Nl) to adjust their mate acceptance in response to previous unsuccessful courtship by heterospecific males. We show that Nl females are more reluctant to mate with a conspecific male when having been courted previously by a heterospecific male, but Nv females are not. We argue that this strategy is reasonable for Nl females but not for Nv females, which follow a different strategy to avoid the fitness costs imposed by heterospecific copulations.

Symbiotic polydnavirus and venom reveal parasitoid to its hyperparasitoids

Symbiotic relationships may provide organisms with key innovations that aid in the establishment of new niches. For example, during oviposition, some species of parasitoid wasps, whose larvae develop inside the bodies of other insects, inject polydnaviruses into their hosts. These symbiotic viruses disrupt host immune responses, allowing the parasitoid's progeny to survive. Here we show that symbiotic polydnaviruses also have a downside to the parasitoid's progeny by initiating a multitrophic chain of interactions that reveals the parasitoid larvae to their enemies. These enemies are hyperparasitoids that use the parasitoid progeny as host for their own offspring. We found that the virus and venom injected by the parasitoid during oviposition, but not the parasitoid progeny itself, affected hyperparasitoid attraction toward plant volatiles induced by feeding of parasitized caterpillars. We identified activity of virus-related genes in the caterpillar salivary gland. Moreover, the virus affected the activity of elicitors of salivary origin that induce plant responses to caterpillar feeding. The changes in caterpillar saliva were critical in inducing plant volatiles that are used by hyperparasitoids to locate parasitized caterpillars. Our results show that symbiotic organisms may be key drivers of multitrophic ecological interactions. We anticipate that this phenomenon is widespread in nature, because of the abundance of symbiotic microorganisms across trophic levels in ecological communities. Their role should be more prominently integrated in community ecology to understand organization of natural and managed ecosystems, as well as adaptations of individual organisms that are part of these communities.

Expression of lima bean terpene synthases in rice enhances recruitment of a beneficial enemy of a major rice pest

Volatile terpenoids play a key role in plant defence against herbivory by attracting parasitic wasps. We identified seven terpene synthase genes from lima bean, Phaseolus lunatus L. following treatment with either the elicitor alamethicin or spider mites, Tetranychus cinnabarinus. Four of the genes (Pltps2, Pltps3, Pltps4 and Pltps5) were up-regulated with their derived proteins phylogenetically clustered in the TPS-g subfamily and PlTPS3 positioned at the base of this cluster. Recombinant PlTPS3 was able to convert geranyl diphosphate and farnesyl diphosphate to linalool and (E)-nerolidol, the latter being precursor of the homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). Recombinant PlTPS4 showed a different substrate specificity and produced linalool and (E)-nerolidol, as well as (E,E)-geranyllinalool from geranylgeranyl diphosphate. Transgenic rice expressing Pltps3 emitted significantly more (S)-linalool and DMNT than wild-type plants, whereas transgenic rice expressing Pltps4 produced (S)-linalool, DMNT and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT). In laboratory bioassays, female Cotesia chilonis, the natural enemy of the striped rice stemborer, Chilo suppressalis, were significantly attracted to the transgenic plants and their volatiles. We further confirmed this with synthetic blends mimicking natural rice volatile composition. Our study demonstrates that the transformation of rice to produce volatile terpenoids has the potential to enhance plant indirect defence through natural enemy recruitment.

Spread and global population structure of the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) and its larval parasitoids Diadegma semiclausum and Diadegma fenestrale (Hymenoptera: Ichneumonidae) based on mtDNA

The diamondback moth (DBM) (Plutella xylostella) is one of the main pests of brassicaceous crops worldwide and shows resistance against a wide range of synthetic insecticides incurring millions of dollars in control costs every year. The DBM is a prime example of the introduction of an exotic species as a consequence of globalization. In this study we analyzed the genetic population structure of the DBM and two of its parasitic wasps, Diadegma semiclausum and Diadegma fenestrale, based on mitochondrial DNA sequences. We analyzed DBM samples from 13 regions worldwide (n = 278), and samples of the two wasp species from six European and African countries (n = 131), in an attempt to reconstruct the geographic origin and phylogeography of the DBM and its two parasitic wasps. We found high variability in COI sequences in the diamondback moth. Haplotype analysis showed three distinct genetic clusters, one of which could represent a cryptic species. Mismatch analysis confirmed the hypothesized recent spread of diamondback moths in North America, Australia and New Zealand. The highest genetic variability was found in African DBM samples. Our data corroborate prior claims of Africa as the most probable origin of the species but cannot preclude Asia as an alternative. No genetic variability was found in the two Diadegma species. The lack of variability in both wasp species suggests a very recent spread of bottlenecked populations, possibly facilitated by their use as biocontrol agents. Our data thus also contain no signals of host-parasitoid co-evolution.

The rearranged mitochondrial genome of Leptopilina boulardi (Hymenoptera: Figitidae), a parasitoid wasp of Drosophila

The partial mitochondrial genome sequence of Leptopilina boulardi (Hymenoptera: Figitidae) was characterized. Illumina sequencing was used yielding 35,999,679 reads, from which 102,482 were utilized in the assembly. The length of the sequenced region of this partial mitochondrial genome is 15,417 bp, consisting of 13 protein-coding, two rRNA, and 21tRNA genes (the trnaM failed to be sequenced) and a partial A+T-rich region. All protein-coding genes start with ATN codons. Eleven protein-coding genes presented TAA stop codons, whereas ND6 and COII that presented TA, and T nucleotides, respectively. The gene pattern revealed extensive rearrangements compared to the typical pattern generally observed in insects. These rearrangements involve two protein-coding and two ribosomal genes, along with the 16 tRNA genes. This gene order is different from the pattern described for Ibalia leucospoides (Ibaliidae, Cynipoidea), suggesting that this particular gene order can be variable among Cynipoidea superfamily members. A maximum likelihood phylogenetic analysis of the main groups of Apocrita was performed using amino acid sequence of 13 protein-coding genes, showing monophyly for the Cynipoidea superfamily within the Hymenoptera phylogeny.

Singing on the wings! Male wing fanning performances affect female willingness to copulate in the aphid parasitoid Lysiphlebus testaceipes (Hymenoptera: Braconidae: Aphidiinae)

Lysiphlebus testaceipes (Hymenoptera: Braconidae: Aphidiinae) is a generalist endoparasitoid attacking more than 100 aphid species. In L. testaceipes, wing fanning is a main male courtship display evoked by a female-borne sex pheromone. However, no information is available on the characteristics and behavioral role of male fanning during courtship in this parasitoid. Here, the courtship behavior of a wild strain of L. testaceipes was quantified and the male wing fanning performances were analyzed through high-speed video recordings and examined in relation to mating success. Courtship sequence of wild L. testaceipes did not substantially differ from that previously reported for other populations mass reared on aphids. We observed that the male courtship duration did not affect mating success. However, video analysis revealed that the males producing high-frequency fanning signals achieved higher mating success over those that display low-frequency fanning. Wing fanning before successful and unsuccessful courtship differed in amplitude of wing movements and alignment toward the mate, highlighting that frontal courtship positively influence the female mating decisions. This study increases knowledge on sexual behavior in a key parasitoid of aphids, highlighting the importance of wing fanning among the range of sensory modalities used in the sexual communication of L. testaceipes. From a practical point of view, this information is useful in L. testaceipes-based biocontrol strategies, since it can help to establish parameters for quality checking of mass-reared wasps over time.

Mitochondrial genome of Megaphragma amalphitanum (Hymenoptera: Trichogrammatidae)

The mitochondrial genome of the parasitic wasp Megaphragma amalphitanum is published in this paper. The mitochondrial DNA (mtDNA) is 15 041 base pairs (bp) in length and contained 13 protein-coding genes, 2 rRNA genes and 22 tRNA genes. The overall base composition of the genome in descending order was 45.67% A, 8.71% C, 39.63% T and 5.99% G, with a significant AT bias of 85.30%.

Differentially expressed genes linked to natural variation in long-term memory formation in Cotesia parasitic wasps

Even though learning and memory are universal traits in the Animal Kingdom, closely related species reveal substantial variation in learning rate and memory dynamics. To determine the genetic background of this natural variation, we studied two congeneric parasitic wasp species, Cotesia glomerata and C. rubecula, which lay their eggs in caterpillars of the large and small cabbage white butterfly. A successful egg laying event serves as an unconditioned stimulus (US) in a classical conditioning paradigm, where plant odors become associated with the encounter of a suitable host caterpillar. Depending on the host species, the number of conditioning trials and the parasitic wasp species, three different types of transcription-dependent long-term memory (LTM) and one type of transcription-independent, anesthesia-resistant memory (ARM) can be distinguished. To identify transcripts underlying these differences in memory formation, we isolated mRNA from parasitic wasp heads at three different time points between induction and consolidation of each of the four memory types, and for each sample three biological replicates, where after strand-specific paired-end 100 bp deep sequencing. Transcriptomes were assembled de novo and differential expression was determined for each memory type and time point after conditioning, compared to unconditioned wasps. Most differentially expressed (DE) genes and antisense transcripts were only DE in one of the LTM types. Among the DE genes that were DE in two or more LTM types, were many protein kinases and phosphatases, small GTPases, receptors and ion channels. Some genes were DE in opposing directions between any of the LTM memory types and ARM, suggesting that ARM in Cotesia requires the transcription of genes inhibiting LTM or vice versa. We discuss our findings in the context of neuronal functioning, including RNA splicing and transport, epigenetic regulation, neurotransmitter/peptide synthesis and antisense transcription. In conclusion, these brain transcriptomes provide candidate genes that may be involved in the observed natural variation in LTM in closely related Cotesia parasitic wasp species.

Ongoing ecological speciation in Cotesia sesamiae, a biological control agent of cereal stem borers

To develop efficient and safe biological control, we need to reliably identify natural enemy species, determine their host range, and understand the mechanisms that drive host range evolution. We investigated these points in Cotesia sesamiae, an African parasitic wasp of cereal stem borers. Phylogenetic analyses of 74 individual wasps, based on six mitochondrial and nuclear genes, revealed three lineages. We then investigated the ecological status (host plant and host insect ranges in the field, and host insect suitability tests) and the biological status (cross-mating tests) of the three lineages. We found that one highly supported lineage showed all the hallmarks of a cryptic species. It is associated with one host insect, Sesamia nonagrioides, and is reproductively isolated from the other two lineages by pre- and postmating barriers. The other two lineages had a more variable phylogenetic support, depending on the set of genes; they exhibited an overlapping and diversified range of host species and are not reproductively isolated from one another. We discuss the ecological conditions and mechanisms that likely generated this ongoing speciation and the relevance of this new specialist taxon in the genus Cotesia for biological control.

Experimental conversion of a defensin into a neurotoxin: implications for origin of toxic function

Scorpion K(+) channel toxins and insect defensins share a conserved three-dimensional structure and related biological activities (defense against competitors or invasive microbes by disrupting their membrane functions), which provides an ideal system to study how functional evolution occurs in a conserved structural scaffold. Using an experimental approach, we show that the deletion of a small loop of a parasitoid venom defensin possessing the "scorpion toxin signature" (STS) can remove steric hindrance of peptide-channel interactions and result in a neurotoxin selectively inhibiting K(+) channels with high affinities. This insect defensin-derived toxin adopts a hallmark scorpion toxin fold with a common cysteine-stabilized α-helical and β-sheet motif, as determined by nuclear magnetic resonance analysis. Mutations of two key residues located in STS completely diminish or significantly decrease the affinity of the toxin on the channels, demonstrating that this toxin binds to K(+) channels in the same manner as scorpion toxins. Taken together, these results provide new structural and functional evidence supporting the predictability of toxin evolution. The experimental strategy is the first employed to establish an evolutionary relationship of two distantly related protein families.

Elucidating Structure-Bioactivity Relationships of Methyl-Branched Alkanes in the Contact Sex Pheromone of the Parasitic Wasp Lariophagus distinguendus

The exoskeletons of insects are covered by complex mixtures of cuticular hydrocarbons (CHCs) which are involved in social and sexual communication. However, little is known about the relationship between the structures of CHCs and their behavioral activity. The key component of the contact sex pheromone of the parasitoid Lariophagus distinguendus is 3-methylheptacosane (3-MeC27), which is present in CHC profiles of both females and newly emerged males. The CHCs of females and young males elicit wing-fanning behavior in older males. However, as young males age, 3-MeC27 disappears from their CHC profiles and they no longer elicit wing-fanning responses from other males. We applied enantiopure 3-MeC27 and structurally related CHCs (with respect to chain length or methyl-branch position) to the cuticle of aged male dummies and recorded the wing-fanning behavior of responding males. Only the two enantiomers of 3-MeC27 restored the dummies' attractiveness. The addition of structurally related CHCs or various n-alkanes to bioactive dummies of young males and females significantly decreased wing-fanning by test males. Hence, L. distinguendus males respond specifically but not enantioselectively to 3-MeC27, and perceive the CHC profiles as a whole. Both removal (as is the case with 3-MeC27 in aging males) and addition of individual compounds may disrupt the behavioral response.

Host-habitat location by the parasitoid, Nasonia vitripennis Walker (Hymenoptera: Pteromalidae)

This study investigated the role of odorant cues used during host-habitat location by the generalist parasitoid, Nasonia vitripennis Walker. Nasonia vitripennis is a common parasitoid of Dipteran pupae found in association with decaying carrion. Behavioral assays were used to investigate the host-habitat searching behavior under different scenarios. First, we demonstrated N. vitripennis to be significantly attracted toward odorant cues associated with decaying meat. The biological activity of nine of the volatile molecules constituting the odor of decaying meat was tested on the searching behavior of parasitoid females through two complementary chemoecological approaches: electroantennography (EAG) and olfactometry bioassays. Butanoic acid and butan-1-ol elicited high olfactory responses, but no attraction was induced by these two chemicals. Behavioral assays showed that, among the VOCs tested, methyldisulfanylmethane (DMDS) was the only volatile chemical to induce attraction in N. vitripennis.

Comparative analysis of selected genes from Diachasmimorpha longicaudata entomopoxvirus and other poxviruses

The Diachasmimorpha longicaudata entomopoxvirus (DlEPV) is the first symbiotic EPV described from a parasitic wasp. The DlEPV is introduced into the tephritid fruit fly larval host along with the wasp egg at oviposition. We sequenced a shotgun genomic library of the DlEPV DNA and analyzed and compared the predicted protein sequences of eight ORFs with those of selected poxviruses and other organisms. BlastP searches showed that five of these are homologous to poxvirus putative proteins such as metalloprotease, a putative membrane protein, late transcription factor-3, virion surface protein, and poly (A) polymerase (PAP) regulatory small subunit. Three of these are similar to those of other organisms such as the gamma-glutamyltransferase (GGT) of Arabidopsis thaliana, eukaryotic initiation factor 4A (eIF4A) of Caenorhabditis briggsae and lambda phage integrase (lambda-Int) of Enterococcus faecium. Transcription motifs for early (TGA,A/T,XXXXA) or late (TAAATG, TAAT, or TAAAT) gene expression conserved in poxviruses were identified with those ORFs. Phylogenetic analysis of multiple alignments of five ORFs and 20 poxvirus homologous sequences and of a concatenate of multiple alignments suggested that DlEPV probably diverged from the ancestral node between the fowlpox virus and the genus B, lepidopteran and orthopteran EPVs, to which Amsacta moorei and Melanoplus sanguinipes EPV, respectively, belong. The DlEPV putative GGT, eIF4A, and lambda-Int contained many conserved domains that typified these proteins. These homologues may be involved in either viral pathogenicity or enhancing parasitism via the gamma-glutamyl cycle and compensation of eIF4A levels in the parasitized fly, or via the integration of a portion of the viral genome into the wasp and/or parasitized fly.