Transcriptomic Analysis Following Artificial Selection for Grasshopper Size.

We analyzed the transcriptomes of Romalea microptera grasshoppers after 8 years of artificial selection for either long or short thoraces. Evolution proceeded rapidly during the experiment, with a 13.3% increase and a 32.2% decrease in mean pronotum lengths (sexes combined) in the up- and down-selected colonies, respectively, after only 11 generations. At least 16 additional traits also diverged between the two colonies during the selection experiment. Transcriptomic analysis identified 693 differentially expressed genes, with 386 upregulated and 307 downregulated (55.7% vs. 44.3%), including cellular process, metabolic process, binding, general function prediction only, and signal transduction mechanisms. Many of the differentially expressed genes (DEGs) are known to influence animal body size.

Antiparasitic Properties of Cantharidin and the Blister Beetle Berberomeloe majalis (Coleoptera: Meloidae).

Cantharidin (CTD) is a toxic monoterpene produced by blister beetles (Fam. Meloidae) as a chemical defense against predators. Although CTD is highly poisonous to many predator species, some have evolved the ability to feed on poisonous Meloidae, or otherwise beneficially use blister beetles. Great Bustards, Otis tarda, eat CTD-containing Berberomeloe majalis blister beetles, and it has been hypothesized that beetle consumption by these birds reduces parasite load (a case of self-medication). We examined this hypothesis by testing diverse organisms against CTD and extracts of B. majalis hemolymph and bodies. Our results show that all three preparations (CTD and extracts of B. majalis) were toxic to a protozoan (Trichomonas vaginalis), a nematode (Meloidogyne javanica), two insects (Myzus persicae and Rhopalosiphum padi) and a tick (Hyalomma lusitanicum). This not only supports the anti-parasitic hypothesis for beetle consumption, but suggests potential new roles for CTD, under certain conditions.

Molecular Ecological Basis of Grasshopper (Oedaleus asiaticus) Phenotypic Plasticity under Environmental Selection.

While ecological adaptation in insects can be reflected by plasticity of phenotype, determining the causes and molecular mechanisms for phenotypic plasticity (PP) remains a crucial and still difficult question in ecology, especially where control of insect pests is involved. Oedaleus asiaticus is one of the most dominant pests in the Inner Mongolia steppe and represents an excellent system to study phenotypic plasticity. To better understand ecological factors affecting grasshopper phenotypic plasticity and its molecular control, we conducted a full transcriptional screening of O. asiaticus grasshoppers reared in four different grassland patches in Inner Mongolia. Grasshoppers showed different degrees of PP associated with unique gene expressions and different habitat plant community compositions. Grasshopper performance variables were susceptible to habitat environment conditions and closely associated with plant architectures. Intriguingly, eco-transcriptome analysis revealed five potential candidate genes playing important roles in grasshopper performance, with gene expression closely relating to PP and plant community factors. By linking the grasshopper performances to gene profiles and ecological factors using canonical regression, we first demonstrated the eco-transcriptomic architecture (ETA) of grasshopper phenotypic traits (ETAGPTs). ETAGPTs revealed plant food type, plant density, coverage, and height were the main ecological factors influencing PP, while insect cuticle protein (ICP), negative elongation factor A (NELFA), and lactase-phlorizin hydrolase (LCT) were the key genes associated with PP. Our study gives a clear picture of gene-environment interaction in the formation and maintenance of PP and enriches our understanding of the transcriptional events underlying molecular control of rapid phenotypic plasticity associated with environmental variability. The findings of this study may also provide new targets for pest control and highlight the significance of ecological management practice on grassland conservation.

Diet alters performance and transcription patterns in Oedaleus asiaticus (Orthoptera: Acrididae) grasshoppers.

We reared Oedaleus asiaticus grasshoppers under four different single-plant diets to examine the relationships among diet, performance, stress, and transcription patterns. Grasshoppers fed only Artemisia frigida (Asteraceae) were stressed, as indicated by their lower growth, size, development, and survival, in comparison to grasshoppers fed on any of three grasses, Cleistogenes squarrosa, Leymus chinensis, or Stipa krylovii (all Poaceae). We then used transcriptome analysis to examine how gene expression levels in O. asiaticus were altered by feeding on these diets. Nymphs fed A. frigida had the largest variation in gene expression profiles with a total of 299 genes significantly up- or down-regulated compared to those feeding on the three grasses: down-regulated genes included those involved in cuticle biosynthesis, DNA replication, biosynthesis and metabolism of nutrition. The up-regulated genes included stress-resistant and detoxifying enzymes. GO and KEGG enrichment analysis also showed that feeding on A. frigida could down-regulate biosynthesis and metabolism related pathways, and up-regulate stress-resistant and detoxification terms and pathways. Our results show that diet significantly altered gene-expression, and that unfavorable, stressful diets induce more transcriptional changes than favorable diets. Altered gene-expression represents phenotypic plasticity, and many such changes appear to be evolved, adaptive responses. The ease and regularity by which individuals shift phenotypes via altered transcription suggests that populations consist not of similar, fixed phenotypes, but of a collection of ever-changing, divergent phenotypes.

Biochemical basis of synergism between pathogenic fungus Metarhizium anisopliae and insecticide chlorantraniliprole in Locusta migratoria (Meyen).

We challenged Locusta migratoria (Meyen) grasshoppers with simultaneous doses of both the insecticide chlorantraniliprole and the fungal pathogen, Metarhizium anisopliae. Our results showed synergistic and antagonistic effects on host mortality and enzyme activities. To elucidate the biochemical mechanisms that underlie detoxification and pathogen-immune responses in insects, we monitored the activities of 10 enzymes. After administration of insecticide and fungus, activities of glutathione-S-transferase (GST), general esterases (ESTs) and phenol oxidase (PO) decreased in the insect during the initial time period, whereas those of aryl acylamidase (AA) and chitinase (CHI) increased during the initial period and that of acetylcholinesterase (AChE) increased during a later time period. Activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) decreased at a later time period post treatment. Interestingly, treatment with chlorantraniliprole and M. anisopliae relieved the convulsions that normally accompany M. anisopliae infection. We speculate that locust mortality increased as a result of synergism via a mechanism related to Ca(2+) disruption in the host. Our study illuminates the biochemical mechanisms involved in insect immunity to xenobiotics and pathogens as well as the mechanisms by which these factors disrupt host homeostasis and induce death. We expect this knowledge to lead to more effective pest control.

Transcriptomic and proteomic analysis of pre-diapause and non-diapause eggs of migratory locust, Locusta migratoria L. (Orthoptera: Acridoidea).

Low temperature induces diapause in locusts. However, the physiological processes and initiation mechanism of diapause are not well understood. To understand the molecular basis of diapause, 'omics' analyses were performed to examine the differences between diapause and non-diapause eggs at both transcriptional and translational levels. Results indicated that a total of 62,241 mRNAs and 212 proteins were differentially expressed. Among them, 116 transcripts had concurrent transcription and translation profiles. Up-regulated genes related to diapause included glutathiones-S-transferase et al., and down-regulated genes including juvenile hormone esterase-like protein et al. KEGG analysis mapped 7,243 and 99 differentially expressed genes and proteins, to 83 and 25 pathways, respectively. Correlation enriched pathways indicated that there were nine identical pathways related to diapause. Gene Ontology analysis placed these genes and proteins into three categories, and a higher proportion of genes related to metabolism was up-regulated than down-regulated. Furthermore, three up-regulated pathways were linked to cryoprotection. This study demonstrates the applicability of high-throughput omics tools to identify molecules linked to diapause in the locust. In addition, it reveals cellular metabolism in diapause eggs is more active than in non-diapause eggs, and up-regulated enzymes may play roles in cryoprotection and storing energy for diapause and post-diapause stages.

Gain and loss of multiple functionally related, horizontally transferred genes in the reduced genomes of two microsporidian parasites.

Microsporidia of the genus Encephalitozoon are widespread pathogens of animals that harbor the smallest known nuclear genomes. Complete sequences from Encephalitozoon intestinalis (2.3 Mbp) and Encephalitozoon cuniculi (2.9 Mbp) revealed massive gene losses and reduction of intergenic regions as factors leading to their drastically reduced genome size. However, microsporidian genomes also have gained genes through horizontal gene transfers (HGT), a process that could allow the parasites to exploit their hosts more fully. Here, we describe the complete sequences of two intermediate-sized genomes (2.5 Mbp), from Encephalitozoon hellem and Encephalitozoon romaleae. Overall, the E. hellem and E. romaleae genomes are strikingly similar to those of Encephalitozoon cuniculi and Encephalitozoon intestinalis in both form and content. However, in addition to the expected expansions and contractions of known gene families in subtelomeric regions, both species also were found to harbor a number of protein-coding genes that are not found in any other microsporidian. All these genes are functionally related to the metabolism of folate and purines but appear to have originated by several independent HGT events from different eukaryotic and prokaryotic donors. Surprisingly, the genes are all intact in E. hellem, but in E. romaleae those involved in de novo synthesis of folate are all pseudogenes. Overall, these data suggest that a recent common ancestor of E. hellem and E. romaleae assembled a complete metabolic pathway from multiple independent HGT events and that one descendent already is dispensing with much of this new functionality, highlighting the transient nature of transferred genes.

Divergent egg physiologies in two closely related grasshopper species: Taeniopoda eques versus Romalea microptera (Orthoptera: Romaleidae).

We compared egg survivorship and egg development time at different soil moistures for two closely related grasshopper species from divergent habitats: marsh-inhabiting Romalea microptera (Beauvois) versus desert-inhabiting Taeniopoda eques (Burmeister). These two species can interbreed and produce viable offspring. In nature, both species have a similar 8-9 mo subterranean egg stage, but their soil environments differ dramatically in water content. We predicted that the eggs of the two species would exhibit differential survivorship and development times under different moisture levels. Our laboratory results show that the eggs of both species survived a wide range of soil moistures (≈ 0.5 to 90%), maintained for 3 mo. However, the eggs of the marsh grasshopper, R. microptera, better tolerated the highest soil moistures (95 and 100%), whereas the eggs of the desert species, T. eques, better tolerated the lowest soil moistures (0.0 and 0.1%). Sixty-five percent of marsh-inhabiting R. microptera eggs, but no desert T. eques eggs, survived 3 mo submersion under water. In contrast, 49% of desert T. eques eggs, but only 3.5% of R. microptera eggs, survived after being laid into oven-dried sand and then maintained with no additional water until hatch. In the laboratory at 26 °C, the two species differed significantly in the mean length of the oviposition-to-hatch interval: 176 d for R. microptera versus 237 d for T. eques. These divergent traits presumably benefit these insects in their divergent habitats. Our results suggest the evolution of physiological divergence that is consistent with adaptations to local environments.

A new Encephalitozoon species (Microsporidia) isolated from the lubber grasshopper, Romalea microptera (Beauvois) (Orthoptera: Romaleidae).

We describe a new microsporidian species, Encephalitozoon romaleae n. sp., isolated from an invertebrate host, the grasshopper Romalea microptera, collected near Weeks Island, Louisiana, and Jacksonville, Florida. This microsporidian is characterized by specificity to the gastric caecae and midgut tissues of the host and a life cycle that is nearly identical to that of Encephalitozoon hellem and Encephalitozoon cuniculi. Mature spores are larger (3.97 x 1.95 microm) than those of other Encephalitozoon species. Polar filament coils number 7 to 8 in a single row. Analysis of the small subunit (SSU) rDNA shows that E. romaleae fits well into the Encephalitozoon group and is a sister taxon to E. hellem. This is the first Encephalitozoon species that has been shown to complete its life cycle in an invertebrate host.

Phylogenetic characterization of Encephalitozoon romaleae (Microsporidia) from a grasshopper host: relationship to Encephalitozoon spp. infecting humans.

Encephalitozoon species are the most common microsporidian pathogens of humans and domesticated animals. We recently discovered a new microsporidium, Encephalitozoon romaleae, infecting the eastern lubber grasshopper Romalea microptera. To understand its evolutionary relationships, we compared partial gene sequences of alpha- and beta-tubulin and methionine aminopeptidase 2 enzyme from this and related species. We also analyzed the rRNA internal transcribed spacer. Based on tubulin and MetAP-2 gene phylogenetic analysis, E. romaleae clustered with the Encephalitzoon group with strong bootstrap support (>99%). Within the Encephalitozoon clade, E. romaleae clustered with Encephalitozoon hellem for both the beta-tubulin and MetAP-2 phylogenies based on ML tree. The alpha-tubulin based ML tree, however, placed the new microsporidium closer to Encephalitozoon cuniculi. The rRNA internal transcribed spacer region of E. romaleae has 91% homology with E. hellem.

Testing intra-hemocelic injection of antimicrobials against Encephalitozoon sp. (Microsporidia) in an insect host.

Encephalitozoon spp. are the primary microsporidial pathogens of humans and domesticated animals. In this experiment, we test the efficacy of four commercial antimicrobials against an Encephalitozoon sp. in an insect host by intra-hemocelic injection. All four antimicrobials, viz., thiabendazole, quinine, albendazole, and fumagillin, significantly reduced but did not eliminate microsporidia spore counts in the grasshopper host. Among these four drugs, thiabendazole was most effective in reducing the microsporidia spore level up to 90%, followed by quinine (70%), albendazole (62%), and fumagillin (59%). No control or quinine-treated animals died, whereas 45% of albendazole animals died. Despite the high mortality induced by albendazole, this drug significantly reduced spore counts, a result not seen in previous per os trials. Among the treatment groups, grasshoppers injected with thiabendazole lost a significant mass. Our study suggests that quinine and related alkaloids should be further examined for antimicrosporidial activity.

Sex pheromone of the pine false webworm Acantholyda erythrocephala.

Females of the pine false webworm Acantholyda erythrocephala (L) produce the sex pheromone (Z)-6, 14-pentadecadienal, which attracts flying males in the field. By using gas chromatography coupled with electroantennographic detection (GC-EAD) and mass spectrometry (GC-MS), we detected (Z)-6,14-pentadecadienal in volatile collections and in whole body extracts of female A. erythrocephala. Females, but not males, also exhibited a 25-carbon cuticular hydrocarbon, (Z,Z)-1,9,15-pentacosatriene, which can oxidize to (Z)-6,14-pentadecadienal upon exposure to air and sunlight. (Z,Z)-1,9,15-Pentacosatriene and (Z)-6,14-pentadecadienal identifications were corroborated by comparison with synthetic standards. (Z)-6, 14-Pentadecadienal is the second pheromone identified for pamphilliid sawflies, and the first to elicit strong field attraction, and thus offer potential as a pheromone lure to aid in control of this forest pest.

Effect of four antimicrobials against an Encephalitozoon sp. (Microsporidia) in a grasshopper host.

Encephalitozoon spp. are the primary microsporidial pathogens of humans and domesticated animals. In this experiment, we test the efficacy of 4 commercial antimicrobials against an Encephalitozoon sp. infecting a grasshopper (Romalea microptera) host. Oral treatment with fumagillin or thiabendazole significantly reduced pathogen spore counts (93% and 88% respectively), whereas spore counts of grasshoppers fed quinine produced a non-significant 53% reduction in spores, and those fed streptomycin a non-significant 29% increase in spores, compared to the control. We observed a moderate dose-response effect for thiabendazole, whereby spore count decreased as drug consumption increased. No thiabendazole-treated animals died, whereas 27% of streptomycin-treated animals died, suggesting that thiabendazole was not toxic at the doses administered. The deaths among streptomycin-treated animals may have been caused by drug toxicity, parasite burden, or both. Although fumagillin and thiabendazole significantly reduced spore counts, in no individual was the pathogen totally eliminated. Our data confirm that microsporidia are difficult to control and that fumagillin and thiabendazole are partially effective antimicrobials against this group. Our study suggests that quinine and related alkaloids should be further examined for antimicrosporidial activity, and streptomycin should be examined as a possible enhancer of microsporidiosis.

Efficacy of eleven antimicrobials against a gregarine parasite (Apicomplexa: Protozoa).

BACKGROUND: The Apicomplexa are a diverse group of obligate protozoan parasites infesting a wide range of invertebrate and vertebrate hosts including humans. These parasites are notoriously difficult to control and many species continue to evolve resistance to commercial antibiotics. In this study, we sought to find an effective chemotherapeutic treatment against arthropod gregarines (Apicomplexa), and to identify candidate compounds for testing against other groups of protozoan parasites. METHODS: We tested eleven commercial antibiotics against a gregarine parasite of Romalea microptera grasshoppers. Infected insects were fed daily, lettuce containing known amounts of specific antibiotics. On Days 15 or 20, we measured the number of gregarines remaining in the digestive tract of each grasshopper. RESULTS: Treatment with metronidazole and griseofulvin in host insects significantly reduced gregarine counts, whereas, gregarine counts of insects fed, albendazole, ampicillin, chloramphenicol, fumagillin, quinine, streptomycin, sulfadimethoxine, thiabendazole or tetracycline, were not significantly different from the controls. However, albendazole produced a strong, but non-significant reduction in gregarine count, and streptomycin exhibited a non-significant antagonistic trend. CONCLUSION: Our results confirm that gregarine infections are difficult to control and suggest the possibility that streptomycin might aggravate gregarine infection. In addition, the insect system described here, provides a simple, inexpensive, and effective method for screening antibiotics.

New insect system for testing antibiotics.

New and efficient methods to screen antibiotics are needed to counter increased antibiotic resistance in pathogens and the emergence of new diseases. Here we report a new insect model for screening antibiotics in vivo using the grasshopper Romalea microptera. The system is inexpensive, efficient, and flexible, avoids animal-welfare problems, and can be used to test against most major pathogenic groups. We employed this system to test 11 commercial antibiotics against a pathogenic Encephalitozoon species (Microsporidia). Oral treatment with fumagillin or thiabendazole significantly reduced pathogen spore counts, whereas spore counts of grasshoppers fed with albendazole, ampicillin, chloramphenicol, griseofulvin, metronidazole, sulfadimethoxine, or tetracycline were not significantly different from the infected controls. Quinine produced a distinct, but nonsignificant, reduction in spores, and streptomycin a nonsignificant increase in spores. Although 2 antibiotics significantly reduced spore counts, in no case was the pathogen totally eliminated. This study demonstrates the validity of this system as a method to screen antibiotics. It also corroborates the difficulty researchers and physicians have had in treating microsporidia infections, and suggests that quinine and related alkaloid compounds should be further examined as possible therapeutic agents against this group of ubiquitous pathogens. In addition, streptomycin and related compounds should be tested to determine if this widely used antibiotic enhances microsporidiosis.

Starvation affects vitellogenin production but not vitellogenin mRNA levels in the lubber grasshopper, Romalea microptera.

The interaction of juvenile hormone (JH) and nutrition was studied during the oviposition cycle of the Eastern Lubber grasshopper (Romalea microptera). Starvation of females early or in the middle of the cycle inhibited oocyte growth. Starvation for 4 days also reduced hemolymph levels of JH III and vitellogenesis (Vg) to 25% and 15%, respectively, of the levels in fed animals. Likewise, Vg production by fat body fragments incubated in vitro was reduced to 2% of the levels in fed animals and total protein synthesis was reduced to 25%, suggesting that starvation had a stronger effect on Vg synthesis than on protein synthesis. These effects were reversed when starved animals were fed again. However, fat body levels of Vg-mRNA were similar in fed and starved animals, indicating that starvation did not affect transcript levels. We tested whether the decline in JH levels mediated the other starvation effects by infusing animals with JH III or vehicle for 2 days at the onset of starvation. Infusion of JH elevated JH and Vg-mRNA levels 670% and 103%, respectively, above the levels in vehicle-infused animals. However, Vg production and hemolymph levels of Vg were similar to the levels in vehicle-infused animals. These data suggest that JH alone is insufficient to stimulate Vg production.

Sequestration of glucosinolates by harlequin bug Murgantia histrionica.

Murgantia histrionica, the harlequin bug, is an aposematic pentatomid that feeds on toxic crucifer plants. By performing predator trials, we found that the bugs are distasteful to several species of bird predators. Given this, we tested the hypothesis that the bugs sequester toxins from the crucifer plants they feed on for use in defense against predation. We used high-pressure liquid chromatography for analyses and tested if M. histrionica sequesters toxic chemicals from its crucifer diet. We found that M. histrionica sequesters mustard oil glycosides, precursors to zootoxic mephitic nitriles, and that sequestration is characteristic of the plant species fed upon. Glucosinolate titers in M. histrionica bodies were 20-30 times higher than in their guts. We found that cabbage-fed M. histrionica had higher titers of cabbage glucosinolates than bugs that were fed on a cabbage diet and then switched to a diet of garden nasturtium. This indicates that M. histrionica immediately sequesters chemicals from whichever plant it feeds upon. The study shows that M. histrionica can sequester glucosinolates from its host plants for use in defense against predation and that the bugs can retain the glucosinolates for an extended period of time.

Chemical defense in the plant bug Lopidea robiniae (Uhler).

Secretions from the metathoracic glands (MTG) of the black locust bug, Lopidea robiniae (Uhler) (Heteroptera: Miridae) contained six major compounds, including (E)-2-hexenal, (E)-2-hexen-1-ol, (E)-2-octenal, (E)-2-octen-1-ol (E)-2-heptenal, and (Z)-3-octen-1-ol. Males and females did not differ significantly in the relative compositions of identified compounds. In feeding trials, six bird species [robin (Turdus migratorious), blue jay (Cyanocitta cristata), brown thrasher (Toxostoma rufum), killdeer (Charadrius vociferus), starling (Sturnus vulgaris), and house wren (Troglodytes aedon)] demonstrated feeding aversions towards L. robiniae implying that black locust bugs are chemically defended. Bugs discharged the liquid contents of their MTG when attacked, thereby producing a strong and distinct odor. Some birds immediately ejected bugs out of their mouth after biting them, suggesting that the MTG secretion was a deterrent.

Morphology of male sex organs and insemination in the grasshopper Taeniopoda eques (Burmeister).

The functional morphology of the male genitalia and the insemination process of Taeniopoda eques were examined using scanning electron microscopy and dissections of mating pairs. Male accessory glands consist of 17 separate tubules belonging to eight categories. Males attach to females via a genital locking mechanism, with special motions of the four aedeagal valves aiding in insertion of the aedeagus. The male passes a series of spermatophores. Each is emptied of its spermatodesm contents, then extracted from the male and female genital tracts through motions of the aedeagal valves, while the pair remain in copulo. This allows the male to keep a strong hold on the female, presumably preventing usurpation by other males, while filling the spermatheca with sperm.