Lygaeidae Research Articles

Escalation by duplication: Milkweed bug trumps Monarch butterfly.

The iconic Monarch butterfly is probably the best-known example of chemical defence against predation, as pictures of vomiting naive blue jays in countless textbooks vividly illustrate. Larvae of the butterfly take up toxic cardiac glycosides from their milkweed hostplants and carry them over to the adult stage. These compounds (cardiotonic steroids, including cardenolides and bufadienolides) inhibit the animal transmembrane sodium-potassium ATPase (Na,K-ATPase), but the Monarch enzyme resists this inhibition thanks to amino acid substitutions in its catalytic alpha-subunit. Some birds also have substitutions and can feast on cardiac glycoside-sequestering insects with impunity. A flurry of recent work has shown how the alpha-subunit gene has been duplicated multiple times in separate insect lineages specializing in cardiac glycoside-producing plants. In this issue of Molecular Ecology, Herbertz etal. toss the beta-subunit into the mix, by expressing all nine combinations of three alpha- and three beta-subunits of the milkweed bug Na,K-ATPase and testing their response to a cardenolide from the hostplant. The findings suggest that the diversification and subfunctionalization of genes allow milkweed bugs to balance trade-offs between resistance towards sequestered host plant toxins that protect the bugs from predators, and physiological costs in terms of Na,K-ATPase activity.

Cardenolides in the defensive fluid of adult large milkweed bugs have differential potency on vertebrate and invertebrate predator Na+/K+-ATPases.

Aposematic animals rely on diverse secondary metabolites for defence. Various hypotheses, such as competition, life history and multifunctionality, have been posited to explain defence variability and diversity. We investigate the compound selectivity hypothesis using large milkweed bugs, Oncopeltus fasciatus, to determine if distinct cardenolides vary in toxicity to different predators. We quantify cardenolides in the bug's defensive secretions and body tissues and test the individual compounds against predator target sites, the Na+/K+-ATPases, that are predicted to differ in sensitivity. Frugoside, gofruside, glucopyranosyl frugoside and glucopyranosyl gofruside were the dominant cardenolides in the body tissues of the insects, whereas the two monoglycosidic cardenolides-frugoside and gofruside-were the most abundant in the defensive fluid. These monoglycosidic cardenolides were highly toxic (IC50 < 1 μM) to an invertebrate and a sensitive vertebrate enzyme, in comparison to the glucosylated compounds. Gofruside was the weakest inhibitor for a putatively resistant vertebrate predator. Glucopyranosyl calotropin, found in only 60% of bugs, was also an effective inhibitor of sensitive vertebrate enzymes. Our results suggest that the compounds sequestered by O. fasciatus probably provide consistency in protection against a range of predators and underscore the need to consider predator communities in prey defence evolution.

Оңтүстік-Шығыс Қазақстанның ағаш жартылай қаттықанаттыларының (Hemiptera, Heteroptera) трофикалық байланысы

Arboreal hemiptera are part of the living world, occupying a special place in natural food chain and contacts with many living organisms. As a result of the study of arboreal hemipterans of South-Eastern Kazakhstan, the nutritional relationship of 44 species belonging to 7 families was revealed. As a result of the review of the literature, the biological significance of the trophic relationship of arboreal hemiptera and their role in ecology was determined. In addition, there is a description of the habitat area of them, and the number of generations they produce per year. The purpose of the research is to study the trophic relationships of arboreal hemipterans in South-Eastern Kazakhstan. This research was conducted according to various methods in the field of entomology. 4 species from the family Anthocoridae, 20 species from the family Miridae, 4 species from the family Aradidae, 4 species from the family Lygaeidae, 2 species from the family Coreidae, 3 species from the family Acanthosomatidae and 7 species from the family Pentatomidae have been identified. Among them, 7 species are zoophages, 11 species are zoophytophages, 4 species are mycetophages, 22 species are phytophages (narrow oligophytophages - 6, wide oligophytophages - 7, polyphytophages - 9). The results of the research allow to distinguish useful or harmful species of arboreal hemipterans.

A nutrition-defence trade-off drives diet choice in a toxic plant generalist.

Plant toxicity shapes the dietary choices of herbivores. Especially when herbivores sequester plant toxins, they may experience a trade-off between gaining protection from natural enemies and avoiding toxicity. The availability of toxins for sequestration may additionally trade off with the nutritional quality of a potential food source for sequestering herbivores. We hypothesized that diet mixing might allow a sequestering herbivore to balance nutrition and defence (via sequestration of plant toxins). Accordingly, here we address diet mixing and sequestration of large milkweed bugs (Oncopeltus fasciatus) when they have differential access to toxins (cardenolides) in their diet. In the absence of toxins from a preferred food (milkweed seeds), large milkweed bugs fed on nutritionally adequate non-toxic seeds, but supplemented their diet by feeding on nutritionally poor, but cardenolide-rich milkweed leaf and stem tissues. This dietary shift corresponded to reduced insect growth but facilitated sequestration of defensive toxins. Plant production of cardenolides was also substantially induced by bug feeding on leaf and stem tissues, perhaps benefitting this cardenolide-resistant herbivore. Thus, sequestration appears to drive diet mixing in this toxic plant generalist, even at the cost of feeding on nutritionally poor plant tissue.

Differential accumulation of cardenolides from Asclepias curassavica by large milkweed bugs does not correspond to availability in seeds or biological activity on the bug Na+/K+-ATPase

Milkweed–herbivore systems are characterized by cardenolide chemical defenses and specialized herbivore adaptations such as physiological target site insensitivity. Cardenolide defenses in milkweeds can vary in terms of the total concentration, differences in the polarity of individual cardenolides, and the substitution of the steroidal structures that can contribute to the molecule's reactivity. The variability in cardenolide defenses could represent the plant's response to natural selection and adaptation of resistant herbivores and is a characteristic of phenotype-matching between defensive and offensive traits resulting from coevolution. Here, we test the phenotypic match of the cardenolide composition of seeds of Asclepias curassavica and those sequestered by nymphs and adults of the specialized seed herbivore Oncopeltus fasciatus, combined with tests of the inhibitory capacity of a subset of seed cardenolides against the Na+/K+-ATPase of O. fasciatus and a non-adapted insect (Drosophila melanogaster). We compare this with the inhibitory capacity against the highly sensitive porcine Na+/K+-ATPase. Among the five most abundant cardenolides present in milkweed seeds, glucopyranosyl frugoside, glucopyranosyl gofruside, and glucopyranosyl calotropin were significantly more abundant in the seeds than in the adults and nymphs; the bugs contained higher concentrations of the deglucosylated compounds. The most abundant compound, glucopyranosyl frugoside, was also the most inhibitory for O. fasciatus, but O. fasciatus was significantly more tolerant to all compounds compared to D. melanogaster and the highly sensitive porcine enzyme. Our results add to the evidence that O. fasciatus sequesters specific individual cardenolides from its Asclepias host plants that are not directly linked to the concentration and inhibitory potency.

New Structures, Spectrometric Quantification, and Inhibitory Properties of Cardenolides from Asclepias curassavica Seeds.

Cardiac glycosides are a large class of secondary metabolites found in plants. In the genus Asclepias, cardenolides in milkweed plants have an established role in plant-herbivore and predator-prey interactions, based on their ability to inhibit the membrane-bound Na+/K+-ATPase enzyme. Milkweed seeds are eaten by specialist lygaeid bugs, which are the most cardenolide-tolerant insects known. These insects likely impose natural selection for the repeated derivatisation of cardenolides. A first step in investigating this hypothesis is to conduct a phytochemical profiling of the cardenolides in the seeds. Here, we report the concentrations of 10 purified cardenolides from the seeds of Asclepias curassavica. We report the structures of new compounds: 3-O-β-allopyranosyl coroglaucigenin (1), 3-[4'-O-β-glucopyranosyl-β-allopyranosyl] coroglaucigenin (2), 3'-O-β-glucopyranosyl-15-β-hydroxycalotropin (3), and 3-O-β-glucopyranosyl-12-β-hydroxyl coroglaucigenin (4), as well as six previously reported cardenolides (5-10). We test the in vitro inhibition of these compounds on the sensitive porcine Na+/K+-ATPase. The least inhibitory compound was also the most abundant in the seeds-4'-O-β-glucopyranosyl frugoside (5). Gofruside (9) was the most inhibitory. We found no direct correlation between the number of glycosides/sugar moieties in a cardenolide and its inhibitory effect. Our results enhance the literature on cardenolide diversity and concentration among tissues eaten by insects and provide an opportunity to uncover potential evolutionary relationships between tissue-specific defense expression and insect adaptations in plant-herbivore interactions.

New record of lygaeid bugs of genus Graptostethus Stal (Hemiptera: Heteroptera: Lygaeidae) on Dalbergia sissoo from Jharkhand, India

Two Lygaeid bugs Graptostethus nigriceps Stal and Graptostethus quadrisignatus Distant were noticed to cause considerable damage by sucking the sap of tender shoot, pod and leaves of Dalbergia sissoo in nursery and young plantation in the Birsa Agricultural University, Ranchi, Jharkhand and this finding documents a new record of host plant (Dalbergia sissoo) of these hemipteran bugs of Jharkhand.

Functional evidence supports adaptive plant chemical defense along a geographical cline

Environmental clines in organismal defensive traits are usually attributed to stronger selection by enemies at lower latitudes or near the host's range center. Nonetheless, little functional evidence has supported this hypothesis, especially for coevolving plants and herbivores. We quantified cardenolide toxins in seeds of 24 populations of common milkweed (Asclepias syriaca) across 13 degrees of latitude, revealing a pattern of increasing cardenolide concentrations toward the host's range center. The unusual nitrogen-containing cardenolide labriformin was an exception and peaked at higher latitudes. Milkweed seeds are eaten by specialist lygaeid bugs that are even more tolerant of cardenolides than the monarch butterfly, concentrating most cardenolides (but not labriformin) from seeds into their bodies. Accordingly, whether cardenolides defend seeds against these specialist bugs is unclear. We demonstrate that Oncopeltus fasciatus (Lygaeidae) metabolized two major compounds (glycosylated aspecioside and labriformin) into distinct products that were sequestered without impairing growth. We next tested several isolated cardenolides invitro on the physiological target of cardenolides (Na+/K+-ATPase); there was little variation among compounds in inhibition of an unadapted Na+/K+-ATPase, but tremendous variation in impacts on that of monarchs and Oncopeltus. Labriformin was the most inhibitive compound tested for both insects, but Oncopeltus had the greater advantage over monarchs in tolerating labriformin compared to other compounds. Three metabolized (and stored) cardenolides were less toxic than their parent compounds found in seeds. Our results suggest that a potent plant defense is evolving by natural selection along a geographical cline and targets specialist herbivores, but is met by insect tolerance, detoxification, and sequestration.

Sequestration of Defenses against Predators Drives Specialized Host Plant Associations in Preadapted Milkweed Bugs (Heteroptera: Lygaeinae).

AbstractHost plant specialization across herbivorous insects varies dramatically, but while the molecular mechanisms of host plant adaptations are increasingly known, we often lack a comprehensive understanding of the selective forces that favor specialization. The milkweed bugs (Heteroptera: Lygaeinae) are ancestrally associated with plants of the Apocynaceae from which they commonly sequester cardiac glycosides for defense, facilitated by resistant Na+/K+-ATPases and adaptations for transport, storage, and discharge of toxins. Here, we show that three Lygaeinae species independently colonized four novel nonapocynaceous hosts that convergently produce cardiac glycosides. A fourth species shifted to a new source of toxins by tolerating and sequestering alkaloids from meadow saffron (Colchicum autumnale, Colchicaceae). Across three milkweed bug species tested, feeding on seeds containing toxins did not improve growth or speed of development and even impaired growth and development in two species, but sequestration mediated protection of milkweed bugs against two natural predators: lacewing larvae and passerine birds. We conclude that physiological preadaptations and convergent phytochemistry facilitated novel specialized host associations. Since toxic seeds did not improve growth but either impaired growth or, at most, had neutral effects, selection by predators on sequestration of defenses, rather than the exploitation of additional profitable dietary resources, can lead to obligatory specialized host associations in otherwise generalist insects.

Distinct Developmental Mechanisms Influence Sexual Dimorphisms in the Milkweed Bug Oncopeltus Fasciatus

Distinct Developmental Mechanisms Influence Sexual Dimorphisms in the Milkweed Bug Oncopeltus Fasciatus

Development of the Pre-gnathal Segments in the Milkweed Bug Oncopeltus fasciatus Suggests They Are Not Serial Homologs of Trunk Segments.

The three anterior-most segments in arthropods contain the ganglia that make up the arthropod brain. These segments, the pre-gnathal segments (PGS), are known to exhibit many developmental differences to other segments, believed to reflect their divergent morphology. We have analyzed the expression and function of the genes involved in the conserved segment-polarity network, including genes from the Wnt and Hedgehog pathways, in the PGS, compared with the trunk segments, in the hemimetabolous insect Oncopeltus fasciatus. Gene function was tested by manipulating expression through RNA interference against components of the two pathways. We show that there are fundamental differences in the expression patterns of the segment polarity genes, in the timing of their expression and in the interactions among them in the process of pre-gnathal segment generation, relative to all other segments. We argue that given these differences, the PGS should not be considered serially homologous to trunk segments. This realization raises important questions about the differing evolutionary ancestry of different regions of the arthropod head.

The complete mitochondrial genome of Tropidothorax sinensis (Reuter, 1888) (Hemiptera: Lygaeidae)

The complete mitochondrial genome (mitogenome) of Tropidothorax sinensis (Reuter, 1888) was determined in the present study by using high-throughput sequencing. This mitogenome is 15,422 bp in size and comprises 37 typical coding genes and a control region. All protein-coding genes are initiated with ATN, except for COX1 and ND4L use TTG as the start codon, and terminate with TAA or TAG with the exception of COX2, COX3 and ND1 which use a single T residue as the stop codon. Twenty-one of the 22 transfer RNA genes have the typical clover-leaf structure except for tRNASer(AGN) . The monophyly of the family Lygaeidae and the sister relationship between T. sinensis and T. cruciger is supported by maximum likelihood analysis based on the protein-coding and ribosomal RNA gene sequences.

БИОРАЗНООБРАЗИЕ ПОЛУЖЕСТКОКРЫЛЫХ (HETEROPTERA) ИНФРАОТРЯДА PENTATOMOMORPHA I ИЛЕ-АЛАТАУСКОГО ГОСУДАРСТВЕННОГО НАЦИОНАЛЬНОГО ПРИРОДНОГО ПАРКА

The article presents the results of field research conducted in 2020 on the territory of the Ile-Alatau State National Natural Park. As a result of the conducted research, 32 species belonging to 2 families of hemiptera of the infraorder Pentatomomorpha I were identified. Among them, the predominant species composition of the family Lygaeidae is 21 species (66%), and 11 species are known from the family Aradidae (34%). On trophic specialization, they are divided into mycetophagy (11 species), phytophages (21 species, of which politicology – 16 types, wide oligotherapy – 3, narrow oligotherapy – 2). According to the type of food, both taking into account the number and number of species in the complex of hemiptera, phytophages clearly predominate. According to the number of generations per year, the hemiptera of the Ile-Alatau SNNP are divided into 4 groups: acyclic (different stages of development can be found simultaneously throughout the year) – 11 species, monovoltine (one generation per year) - 15 species, bivoltine (two generations per year) – 5 species, polyvoltine (several generations per year) - 1 species. There are 30 species with mesophilic ecology in the study area, only 1 species is hygromesophilus. Among the hemiptera of the Ile-Alatau GNPP, 19 species (61%) overwinter in the imago stage, 11 species (35%) in the imago and larvae stage, and 1 species (4%) in the egg stage.

Flower pests of cashew, their seasonal incidence, damage and natural enemies

Different insect species attack cashew flowers during different phenological stages of the inflorescences from 511 to 619 of Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale of cashew phenology. A total of 67 species were documented during the investigation between 2016 and 2020. Among all pest groups, Lepidopterans were dominant comprising 32 species followed by Hemipterans with 22 species. The pests newly reported on cashew flowers include Perixera sp., Bombotelia jocosatrix, Gyrtona sp., Gatesclarkeana sp., Ascotis selenaria, Tinolius sp. besides two Cicadellids and two Lygaeid bugs. Damage symptoms, seasonal incidence and natural enemies were also documented for different pests. None of the weather factors had significant relationship with tea mosquito bug (TMB), B. jocosatrix and Lamida moncusalis. Though rainfall had no significant relationship with any of the pest population, number of rainy days had significant negative relationship with apple and nut borer (ANB) (-0.35), beetles (-0.35), thrips (-0.39) and mirids (-0.34). Parasitism by Trathala flavorbitalis on ANB was 15–30%, and by Apanteles sp. on Archips sp. was 20–25%. Reduction in nut set up to 47.06% has been recorded due to inflorescence pests in unsprayed trees compared to sprayed ones under mild infestation of TMB.

Annotated List of the Family Lygaeidae Schilling, 1829 (Heteroptera) in Libya

In this study, subfamilies, genera, and species of Lygaeidae are given, accompanied by synonyms, local and general distribution. This study was carried out during the years 2007-2010 in the country of Libya. This study revealed the presence of 111 species in Libya under 52 genera to 8 subfamilies. 31 are recoded from Libya for the first time in the present study.

Defense of Milkweed Bugs (Heteroptera: Lygaeinae) against Predatory Lacewing Larvae Depends on Structural Differences of Sequestered Cardenolides.

Predators and parasitoids regulate insect populations and select defense mechanisms such as the sequestration of plant toxins. Sequestration is common among herbivorous insects, yet how the structural variation of plant toxins affects defenses against predators remains largely unknown. The palearctic milkweed bug Lygaeus equestris (Heteroptera: Lygaeinae) was recently shown to sequester cardenolides from Adonis vernalis (Ranunculaceae), while its relative Horvathiolus superbus also obtains cardenolides but from Digitalis purpurea (Plantaginaceae). Remarkably, toxin sequestration protects both species against insectivorous birds, but only H. superbus gains protection against predatory lacewing larvae. Here, we used a full factorial design to test whether this difference was mediated by the differences in plant chemistry or by the insect species. We raised both species of milkweed bugs on seeds from both species of host plants and carried out predation assays using the larvae of the lacewing Chrysoperla carnea. In addition, we analyzed the toxins sequestered by the bugs via liquid chromatography (HPLC). We found that both insect species gained protection by sequestering cardenolides from D. purpurea but not from A. vernalis. Since the total amount of toxins stored was not different between the plant species in H. superbus and even lower in L. equestris from D. purpurea compared to A. vernalis, the effect is most likely mediated by structural differences of the sequestered toxins. Our findings indicate that predator–prey interactions are highly context-specific and that the host plant choice can affect the levels of protection to various predator types based on structural differences within the same class of chemical compounds.

A Preliminary Study of Family Lygaeidae from Andhra Pradesh, India

The present paper provides information on 30 species belonging to Lygaeidae family under 20 genera from Andhra Pradesh from the unidentified collections housed in Zoological Survey of India. Of them, 27 species are new records to Andhra Pradesh state. Distribution of each species with measurements and ratios of various body parts were taken as additional diagnostic characters along with key to identification have been provided.

Video surveillance reveals a community of largely nocturnal Danaus plexippus (L.) egg predators

Monarch butterfly (Danaus plexippus L.) declines in eastern North America have prompted milkweed host plant restoration efforts in non-agricultural grasslands. However, grasslands harbor predator communities that exert high predation pressure on monarch eggs and larvae. While diurnal monarch predators are relatively well known, no studies have investigated the contribution of nocturnal monarch predators. We used video cameras to monitor sentinel monarch eggs and fourth instars on milkweed in southern Michigan to identify predators and determine if nocturnally-active species impose significant predation pressure. We observed ten arthropod taxa consuming monarch eggs and larvae, with 74% of egg predation events occurring nocturnally. Taxa observed attacking monarch eggs included European earwigs (Forficula auricularia L.), tree crickets (Oecanthus sp.), lacewing larvae (Neuroptera), plant bugs (Miridae), small milkweed bugs (Lygaeus kalmii Stal), ants (Formicidae), spiders (Araneae: Salticidae and other spp.), harvestmen (Opiliones), and velvet mites (Trombidiformes: Trombidiidae). Larvae were attacked by ground beetles (Calleida sp.), jumping spiders (Araneae: Salticidae), and spined soldier bugs (Podisus maculiventris Say). Our findings provide important information about monarch predator–prey interactions that could be used to develop strategies to conserve monarchs through reducing predation on early life stages.

Are Heteroptera communities able to be bioindicators of urban environments?

The Heteroptera is a group of animals associated with the vegetation cover. The conducted analysis indicates that groups of heteropterans in the urban environment have a pattern of reaction to the environmental factors, determined using the phytoindication method. In the study, we considered the following hypotheses: 1) phytoindicational assessments of ecological factors may explain the patterns of variation of the groups of heteropterans; 2) among Heteroptera species, comparatively homogenous ecological groups could be distinguished which are characterized by similar character of response to the effect of certain environmental factors; 3) these groups could be used for bioindication of the conditions of environment in urban ecosystems. Stationary collection of heteropterans was performed during three years from May to October of 2017–2019 on six plots in Kharkiv. The article describes factors which affect the structure of groups of Heteroptera within the ecosystem of the large city and assess the bioindication possibilities. The data presented in the article, as well as the conclusions drawn, are to a large extent associated with stenotopic species, most of which could be used as bioindicators of the condition of one or another biocenosis. According to the results of a taxonomical survey in the territory of Kharkiv, 180 species of Heteroptera were found, belonging to 120 genera and 17 families. The highest species diversity was seen for the family Miridae, accounting for 50 species (27.0% of the total number of counted species). Fewer species were identified as the representatives of families Lygaeidae – 46 species (24.9%) and Pentatomidae – 23 (12.4%). Family Rhopalidae was represented by 11 species (5.9%). Nabidae and Tingidae – 10 species each (5.4%). Families Coreidae – 8 (4.3%), Cydnidae and Scutelleridae – 4 species each (2.2%), Anthocoridae – 3 (1.6%). The families Berytidae, Piesmatidae, Pyrrhocoridae and Reduviidae were represented by only 2 species each (1.1%). Families Acanthosomatidae, Alydidae and Aradidae were represented by 1 species each, in total accounting for 1.5%. The reasonably high level of species and ecological diversities of Heteroptera in the territory of the city allows them to be used in bioindication studies. We determined comparatively homogenous ecological groups of heteropterans which have a similar pattern of response to the impact of certain environmental factors. The study demonstrates that phytoindicatory assessments of the ecological factors can explain the patterns of variation in groups of heteropterans, We determined the factors which have effects on the structure of the group of heteropterans within the metropolitan ecosystem. The level of their effect on groups of heteropterans within the city is different. The most influential were light and humidity. Comparison of potential and realized projections of ecological space allows us, to a certain extent, to generate hypotheses about the orientations of transformation of the group heteropterans.

ДЕЯКІ ОСОБЛИВОСТІ СЕЗОННИХ ЦИКЛІВ НАПІВТВЕРДОКРИЛИХ (HETEROPTERA) УРБОЦЕНОЗІВ МІСТА ХАРКОВА

The article deals with the analysis of the data on the individual characteristics of the life cycles of Heteroptera recorded in the urban cenoses of Kharkiv. In terms generations, three phenological groups were distinguished and five phenological groups – on the basis of the wintering stage. At the imago stage, 114 species hibernate (69.51% of the entire heteropterofauna), of which most species belong to the families Lygaeidae (37), Miridae (14) and Pentatomidae (22 species), Nabidae, Tingidae, and Rhopalidae (seven species each). At the egg stage, 42 species winter (25.61%), mainly from the Miridae family (34 species), fewer – Lygaeidae, Nabidae, Rhopalidae (two or three species each). At the larval stage, only four species (2.44%) from the Pentatomidae (3) and Reduviidae (1 species) families hibernate. Two species from each group hibernate at the stages of imago and larvae, eggs and larvae. A small number of such species can be explained by the fact that the conditions for wintering at these stages are less favorable in temperate latitudes (Eastern Ukraine). The group of monovoltines includes 107 species of bugs (65.24%). The bivoltine and multivoltine groups are represented by 32 (19.51%) and 24 (14.63% of the entire hetero-fauna) species, respectively. As for Coriomeris denticulatus, the number of their generations per year has not been established.