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PubMed2001

Defensive role of secretion of ectal mandibular glands of the wasp Polistes dominulus.

Ectal mandibular glands of insects are exocrine glands localized in the anterior-lateral region of the head, close to the base of the mandibles. In social wasps, the gland is composed of secretory cells and a reservoir into which the secretion accumulates. At the time of emission the secretion flows onto a specialized cuticular area on the outside of the base of the mandibles. Secretion of Polistes dominulus is emitted only when wasps are greatly disturbed or in the presence of predators, and its function seems to be mainly defensive. Morphometric studies did not reveal any size differences between the glands of the queens and those of the workers. GC-MS analyses of the glands identified 32 compounds, mainly acids and aldehydes in the range C2-C18. The overall odor, caused by the mixture of aldehydes, is distinct. Workers do not respond strongly to the odor. The secretion probably serves as a warning signal to vertebrate predators.

Animals↗
PubMed2025

Genome assembly and annotation of the parasitoid jewel wasp Nasonia oneida.

The jewel wasp, Nasonia (Hymenoptera: Pteromalidae), is a well-established model system for evolutionary genetics and host-microbial interactions. Here, we present the genome of N. oneida, a species lacking prior genomic characterization, using 10× Genomics linked-read (400× coverage), Illumina short-read (120× coverage), and transcriptome data (30× coverage). The assembled genome size is 267 Mb, comprising 4,675 scaffolds, with a scaffold N50 of 1 Mb and 98.40% Benchmarking Universal Single-Copy Orthologues (BUSCOs) completeness score. Annotation revealed 32.29% (86.46 Mb) of repetitive sequences and 14,221 protein-coding genes. Comparative genomics of N. oneida with 15 other hymenopteran species validated the presence of 5,939 gene families shared among them, including 3643 single-copy and 2296 multicopy gene families. This study provides the first de novo assembly of N. oneida, providing a significant addition to the growing repertoire of molecular tools for comparative genomics and functional studies to understand the evolution of closely related species as well as the evolution of parasitic wasps.

Animals↗
PubMed2004

Cytogenetic mechanism and genetic consequences of thelytoky in the wasp Trichogramma cacoeciae.

In Hymenoptera, complete parthenogenesis, that is thelytoky, is a common phenomenon where virgin females produce only daughters. Thelytoky is often induced by bacteria of the genus Wolbachia, but can also be genetically determined by the insect itself, as in the genus Trichogramma where both forms exist. In order to compare these two forms of thelytoky, chromosome behaviour analysis in young eggs and genetic analysis of microsatellite markers were carried out in the wasp Trichogramma cacoeciae, where thelytoky is genetically determined. Microscopic studies revealed that during female gamete formation meiotic cells undergo only a single equational division followed by the expulsion of a single polar body. This absence of meiotic recombination and reduction corresponds well with the high levels of heterozygosity observed in females collected from the field and a nonsegregation pattern in the offspring of heterozygous females. We therefore concluded that diploidy in T. cacoeciae is maintained through an apomictic cloning mechanism and that the incidence of thelytoky under genetic control of the wasp differs entirely from the mechanism induced by Wolbachia infection, where thelytoky is restored through gamete duplication.

Animals↗
PubMed2006

The quantitative genetic basis of polyandry in the parasitoid wasp, Nasonia vitripennis.

Understanding the evolution of female multiple mating (polyandry) is crucial for understanding sexual selection and sexual conflict. Despite this interest, little is known about its genetic basis or whether genetics influences the evolutionary origin or maintenance of polyandry. Here, we explore the quantitative genetic basis of polyandry in the parasitoid wasp Nasonia vitripennis, a species in which female re-mating has been observed to evolve in the laboratory. We performed a quantitative genetic experiment on a recently collected population of wasps. We found low heritabilities of female polyandry (re-mating frequency after 18 h), low heritability of courtship duration and a slightly higher heritability of copulation duration. However, the coefficients of additive genetic variance for these traits were all reasonably large (CV(A)>7.0). We also found considerable dam effects for all traits after controlling for common environment, suggesting either dominance or maternal effects. Our work adds to the evidence that nonadditive genetic effects may influence the evolution of mating behaviour in Nasonia vitripennis, and the evolution of polyandry more generally.

Animals↗
PubMed1999

Mastocytosis associated with severe wasp sting anaphylaxis detected by elevated serum mast cell tryptase levels.

A markedly elevated serum level of mast cell tryptase (77.6 microg/L; 95th percentile in normals 13.5 microg/L) was detected in a patient treated for 5 years with wasp venom immunotherapy because of severe anaphylaxis following a wasp sting. Retrospective analysis of stored serum samples taken during the course of immunotherapy revealed that the tryptase level had been elevated for at least 3 years. Despite several dermatological examinations, skin changes of mastocytosis had been missed. Re-examination of the patient revealed sparse macules on the thorax and thighs; Darier's sign was negative. Histologically, mast cell accumulation in these lesions was demonstrable. No signs of systemic mastocytosis were detected. The most appropriate diagnosis was telangiectasia macularis eruptiva perstans. Even in patients with highly elevated tryptase levels, mastocytosis may go undiagnosed. As mastocytosis predisposes to severe anaphylaxis, the condition should be looked for in patients with such reactions by clinical examination and measurement of serum tryptase levels.

Adult↗
PubMed2003

Application of 16S rDNA-DGGE to examine the microbial ecology associated with a social wasp Vespula germanica.

Invertebrates host numerous bacteria, with interactions ranging from pathogenesis to symbiosis. While certain symbiotic relationships have been well studied, little is known about the dynamics of these bacterial communities. Denaturing gradient gel electrophoresis (DGGE) was used to examine the bacterial microflora associated with the eusocial wasp Vespula germanica. DGGE profiles of larval guts revealed a variable microflora, suggesting that V. germanica is not dependent on a particular suite of mutualists. The variation in profiles was not related to season, nest size or macrohabitat. Sequences corresponding to Lactococcus, Lactobacillus, a novel Leuconostoc and two Rickettsiella grylli strains were obtained. DGGE proved to be a useful technique for characterizing the wasp microflora. Given the importance of microbial communities to invertebrates, there is much to be gained from the application of such techniques.

Animals↗
PubMed2001

Colony kin structure and male production in Dolichovespula wasps.

In annual hymenopteran societies headed by a single outbred queen, paternity (determined by queen mating frequency and sperm use) is the sole variable affecting colony kin structure and is therefore a key predictor of colony reproductive characteristics. Here we investigate paternity and male production in five species of Dolichovespula wasps. Twenty workers from each of 10 colonies of each of five species, 1000 workers in total, were analysed at three DNA microsatellite loci to estimate paternity. To examine the relationship between kin structure and reproductive behaviour, worker ovary activation was assessed by dissection and the maternal origin of adult males was assessed by DNA microsatellites. Effective paternity was low in all species (D. media 1.08, D. maculata 1.0, D. sylvestris 1.15, D. norwegica 1.08 and D. saxonica 1.35), leading to the prediction of queen-worker conflict over male production. In support of this, workers with full-size eggs in their ovaries (four out of five species) and adult males that were workers' sons (all five species) were found in queenright colonies. However, workers were only responsible for a minority of male production (D. media 7.4%, D. maculata 20.9%, D. sylvestris 9.8%, D. norwegica 2.6% and D. saxonica 34.6%) suggesting that the queen maintains considerable reproductive power over the workers. Kin structure and reproductive conflict in Dolichovespula contrast with their sister group Vespula. Dolichovespula is characterized by low paternity, worker reproduction, and queen-worker conflict and Vespula by high paternity, effective worker policing and absence of worker reproduction. The trend revealed by this comparison is as predicted by kin selection theory suggesting that colony kin structure has been pivotal in the evolution of the yellowjacket wasps.

Animals↗
PubMed2003

Differential gene expression in two strains of the endoparasitic wasp Venturia canescens identified by cDNA-amplified fragment length polymorphism analysis.

In the endoparasitic wasp Venturia canescens (Hymenoptera: Ichneumonidae) two genetically distinct lines, which differ at the VLP1 gene locus, appear to coexist sympatrically in thelytokous as well as arrhenotokous field and laboratory strains. Both lines display quite distinct morphological, physiological and behavioural variations, such as different oviposition strategies, egg numbers and growth rates during early embryonic development. To examine whether more than one gene is affected in the two lines, we applied cDNA-amplified fragment length polymorphism analysis to examine patterns of gene expression in ovaries of both wasp lines. We show that a number of ovarian transcripts have an altered expression pattern in either line, which was further confirmed by virtual Northern blot analysis. Sequence analysis of the cDNA-amplified fragment length polymorphism fragments revealed that some of the respective genes are expected to be involved in regulation of protein degradation during stress responses and in signal perception/transduction. The full-length sequence of two transcription factors (a homeodomain containing protein and a zinc finger protein) differentially expressed in both lines was obtained by RACE-polymerase chain reaction and their putative role in regulating key developmental processes during embryogenesis is discussed.

Amino Acid Sequence↗
PubMed2004

Kin discrimination and sex ratios in a parasitoid wasp.

Sex ratio theory provides a clear and simple way to test if nonsocial haplodiploid wasps can discriminate between kin and nonkin. Specifically, if females can discriminate siblings from nonrelatives, then they are expected to produce a higher proportion of daughters if they mate with a sibling. This prediction arises because in haplodiploids, inbreeding (sib-mating) causes a mother to be relatively more related to her daughters than her sons. Here we formally model this prediction for when multiple females lay eggs in a patch, and test it with the parasitoid wasp Nasonia vitripennis. Our results show that females do not adjust their sex ratio behaviour dependent upon whether they mate with a sibling or nonrelative, in response to either direct genetic or a range of indirect environmental cues. This suggests that females of N. vitripennis cannot discriminate between kin and nonkin. The implications of our results for the understanding of sex ratio and social evolution are discussed.

Animals↗
PubMed2004

Information constraints and the precision of adaptation: sex ratio manipulation in wasps.

Sex allocation theory offers excellent opportunities for studying the precision of adaptation. One of the best-supported areas in the field of sex allocation is Hamilton's theory of local mate competition, which predicts female-biased offspring sex ratios when populations are structured such that mating takes place locally before females disperse. As predicted by local mate competition theory, females of numerous species, especially parasitoid wasps, have been shown to lay a less female-biased sex ratio as the number of females simultaneously laying eggs on a patch increases. It has usually been assumed that this sex ratio adjustment comes through individuals adjusting their behavior directly in response to the presence of other females. Here we show that in the parasitoid wasp Nasonia vitripennis, this shift in offspring sex ratios is primarily caused by the presence of eggs laid by other females and to a lesser extent by the presence of other females. We confirm that females are behaving as predicted by theory, but the way in which they do so is not as straightforward as is often assumed. Instead, even when there are multiple females on a patch, individuals still use the cues that are more commonly associated with sex ratio adjustment in response to sequential visits to a patch by females. This result provides a possible explanation for the observed variation in N. vitripennis sex ratios. More generally, it confirms the need to consider the mechanistic basis of a behavior to understand fully its adaptive value.

Adaptation, Physiological↗
PubMed2004

Caste determination in a polyembryonic wasp involves inheritance of germ cells.

Social insects are characterized by the development of castes in which some colony members reproduce whereas others function as altruistic helpers. The conditional switch controlling caste formation usually involves environmental stimuli that act on processes that regulate development of individuals. Unlike other social species, embryos of polyembryonic wasps develop clonally to produce large numbers of genetically identical offspring and two morphologically distinct castes. All embryos in a clone exist in an identical environment, the host, yet develop into either reproductive larvae that mature into adult wasps or soldier larvae whose function is defense. Here, we report that caste determination in Copidosoma floridanum involves inheritance of germ cells. Expression of a C. floridanum homolog (Cf-vas) of the germ cell marker Vasa indicated that the B(4) blastomere in four cell-stage embryos is specified as a primordial germ cell. Vas expression later in development further indicated that embryos developing into reproductive larvae possess primordial germ cells whereas embryos developing into soldier larvae do not. Ablation of the B(4) blastomere resulted in most broods containing only soldiers whereas ablation of other blastomeres produced broods containing both castes. These results indicate that soldier larvae are obligately sterile and reveal a previously unknown role for germ cells in caste formation.

Amino Acid Sequence↗
PubMed2001

Removing symbiotic Wolbachia bacteria specifically inhibits oogenesis in a parasitic wasp.

Wolbachia are bacteria that live in the cells of various invertebrate species to which they cause a wide range of effects on physiology and reproduction. We investigated the effect of Wolbachia infection in the parasitic wasp, Asobara tabida Nees (Hymenoptera, Braconidae). In the 13 populations tested, all individuals proved to be infected by Wolbachia. The removal of Wolbachia by antibiotic treatment had a totally unexpected effect-aposymbiotic female wasps were completely incapable of producing mature oocytes and therefore could not reproduce. In contrast, oogenesis was not affected in treated Asobara citri, a closely related species that does not harbor Wolbachia. No difference between natural symbiotic and cured individuals was found for other adult traits including male fertility, locomotor activity, and size, indicating that the effect on oogenesis is highly specific. We argue that indirect effects of the treatments used in our study (antibiotic toxicity or production of toxic agents) are very unlikely to explain the sterility of females, and we present results showing a direct relationship between oocyte production and Wolbachia density in females. We conclude that Wolbachia is necessary for oogenesis in these A. tabida strains, and this association would seem to be the first example of a transition from facultative to obligatory symbiosis in arthropod-Wolbachia associations.

Animals↗
PubMed2001

A newly discovered bacterium associated with parthenogenesis and a change in host selection behavior in parasitoid wasps.

The symbiotic bacterium Wolbachia pipientis has been considered unique in its ability to cause multiple reproductive anomalies in its arthropod hosts. Here we report that an undescribed bacterium is vertically transmitted and associated with thelytokous parthenogenetic reproduction in Encarsia, a genus of parasitoid wasps. Although Wolbachia was found in only one of seven parthenogenetic Encarsia populations examined, the "Encarsia bacterium" (EB) was found in the other six. Among seven sexually reproducing populations screened, EB was present in one, and none harbored Wolbachia. Antibiotic treatment did not induce male production in Encarsia pergandiella but changed the oviposition behavior of females. Cured females accepted one host type at the same rate as control females but parasitized significantly fewer of the other host type. Phylogenetic analysis based on the 16S rDNA gene sequence places the EB in a unique clade within the Cytophaga-Flexibacter-Bacteroid group and shows EB is unrelated to the Proteobacteria, where Wolbachia and most other insect symbionts are found. These results imply evolution of the induction of parthenogenesis in a lineage other than Wolbachia. Importantly, these results also suggest that EB may modify the behavior of its wasp carrier in a way that enhances its transmission.

Animals↗
PubMed1984

Selective destruction of a host blood cell type by a parasitoid wasp.

Foreign objects that enter the hemocoel of Drosophila melanogaster larvae are encapsulated by one type of blood cell, the lamellocyte, yet eggs of the parasitoid wasp Leptopilina heterotoma remain unencapsulated in D. melanogaster larval hosts that have many lamellocytes. Here we demonstrate that shortly after a female wasp oviposits in the hemocoel the lamellocytes undergo morphological changes and lose their adhesiveness. These affected blood cells are eventually destroyed as the parasitoid egg continues its development. The factor responsible for lamellocyte destruction, lamellolysin, is contained in an accessory gland of the female reproductive system and is injected along with the egg into the host hemocoel. Lamellolysin does not alter the morphology or the defense functions of the other types of blood cells in the host.

Animals↗
PubMed1998

Shifts in the life history of parasitic wasps correlate with pronounced alterations in early development.

Developmental processes have been traditionally viewed to be invariant within higher taxa. However, examples are known whereby closely related species exhibit alterations in early embryogenesis yet appear very similar as adults. Such developmental changes are thought to occur in response to shifts in life history. In insects, the regulation of embryonic development has been intensively studied in model species like Drosophila melanogaster. Previous comparative studies suggest that the developmental processes documented in Drosophila well describe embryogenesis of advanced, holometabolous, insects generally. There have been few attempts, however, to take into account how life history has influenced early development of insects or to characterize early development of species with life histories fundamentally different from flies. Here we compared early development of two species from the same family of parasitic wasps that exhibit very different life histories. Bracon hebetor is an ectoparasite that lays large, yolky eggs on the integument of its host that develop much like the free-living honeybee and Drosophila. In contrast, Aphidius ervi is an endoparasite that lays small and apparently yolk-free eggs that develop in the hemocoel of the host. This wasp exhibits a radically different mode of early development at both the cellular and molecular level from B. hebetor. The developmental changes in A. ervi reflect functional adaptations for its derived life history and argue that departures from the fly paradigm may occur commonly among insects whose eggs develop under conditions different from typical terrestrial species.

Animals↗
PubMed2006

Transactional skew and assured fitness return models fail to predict patterns of cooperation in wasps.

Cooperative breeders often exhibit reproductive skew, where dominant individuals reproduce more than subordinates. Two approaches derived from Hamilton's inclusive fitness model predict when subordinate behavior is favored over living solitarily. The assured fitness return (AFR) model predicts that subordinates help when they are highly likely to gain immediate indirect fitness. Transactional skew models predict dominants and subordinates "agree" on a level of reproductive skew that induces subordinates to join groups. We show the AFR model to be a special case of transactional skew models that assumes no direct reproduction by subordinates. We use data from 11 populations of four wasp species (Polistes, Liostenogaster) as a test of whether transactional frameworks suffice to predict when subordinate behavior should be observed in general and the specific level of skew observed in cooperative groups. The general prediction is supported; in 10 of 11 cases, transactional models correctly predict presence or absence of cooperation. In contrast, the specific prediction is not consistent with the data. Where cooperation occurs, the model accurately predicts highly biased reproductive skew between full sisters. However, the model also predicts that distantly related or unrelated females should cooperate with low skew. This prediction fails: cooperation with high skew is the observed norm. Neither the generalized transactional model nor the special-case AFR model can explain this significant feature of wasp sociobiology. Alternative, nontransactional hypotheses such as parental manipulation and kin recognition errors are discussed.

Animals↗
PubMed1991

The comparative biology of genetic variation for conditional sex ratio behavior in a parasitic wasp, Nasonia vitripennis.

Using genetic markers, we tracked the sex ratio behavior of individual females of the parasitic wasp, Nasonia vitripennis, in foundress groups of size 1, 2, 4, 8 and 16. Comparison of 12 isofemale strains extracted from a natural population reveals significant between-strain heterogeneity of sex ratios produced in all sizes of foundress group. Under simple assumptions about population structure, this heterogeneity results in heterogeneity of fitnesses. The strains differ in their conditional sex ratio behavior (the sex ratio response of a female to foundress groups of different sizes). Females of some strains produce more males as foundress group size increases (up to size eight). Females of another strain produce more males when not alone but do not respond differentially to group size otherwise. Females of two other strains show no conditional sex ratio behavior. Females of only two strains behave differently in foundress groups of size 8 and 16. Correlation and regression analyses indicate that the strains differ significantly in their fit to the predictions of an evolutionarily stable strategy (ESS) model of conditional sex ratio behavior. Such heterogeneity contradicts the notion that females of this species possess conditonal sex ratio behavior that is optimal in the ESS sense. The results imply that this ESS model is useful but not sufficient for understanding the causal basis of the evolution of this behavior in this species. This is the first report on the sex ratio behavior of individual females in multiple foundress groups in any species of parasitic wasp. Data of this type (and not foundress group or "patch" sex ratios) are essential for testing evolutionary models that predict the sex ratio behaviors of individuals. We suggest that a test for an ESS model include the answers to two important questions: 1) is the model quantitatively accurate? and 2) is there reasonable evidence to indicate that natural selection has caused individuals to manifest the ESS behavior?

Animals↗
PubMed1993

Deletion analysis of the selfish B chromosome, Paternal Sex Ratio (PSR), in the parasitic wasp Nasonia vitripennis.

Paternal Sex Ratio (PSR) is a "selfish" B chromosome in the parasitoid wasp Nasonia vitripennis. It is transmitted via sperm, but causes supercondensation and destruction of the paternal chromosomes in early fertilized eggs. Because this wasp has haplodiploid sex determination, the effect of PSR is to convert diploid (female) eggs into haploid (male) eggs that carry PSR. Characterizing its genetic structure is a first step toward understanding mechanisms of PSR action. The chromosome is largely heterochromatic and contains several tandemly repeated DNA sequences that are not present on the autosomes. A deletion analysis of PSR was performed to investigate organization of repeats and location of functional domains causing paternal chromosome destruction. Deletion profiles using probes to PSR-specific repetitive DNA indicate that most repeats are organized in blocks on the chromosome. This study shows that the functional domains of PSR can be deleted, resulting in nonfunctional PSR chromosomes that are transmitted to daughters. A functional domain may be linked with the psr22 repeat, but function may also depend on abundance of PSR-specific repeats on the chromosome. It is hypothesized that the repeats act as a "sink" for a product required for proper paternal chromosome processing. Almost all deletion chromosomes remained either functional of nonfunctional in subsequent generations following their creation. One chromosome was exceptional in that it reverted from nonfunctionality to functionality in one lineage. Transmission rates of nonfunctional deletion chromosomes were high through haploid males, but low through diploid females.

Animals↗