Avoidance of ant chemical traces by spider mites and its interpretation.

Spider mites become easy prey for ants when they leave their protective webs; therefore, the ability to avoid traces of ongoing ant activity should confer a selective advantage to mites. We examined avoidance of ant traces by the spider mites Tetranychus kanzawai and Tetranychus urticae. Both mite species avoided host plant leaves with active traces of Pristomyrmex punctatus or Formica japonica ants. Pristomyrmex punctatus trace avoidance by T. kanzawai lasted for more than 1 h, but not more than 3 h. Tetranychus kanzawai also avoided P. punctatus traces on plant stems, along which the mites access leaves. Moreover, T. kanzawai avoided hexane extracts of P. punctatus or F. japonica applied to a filter paper pathway. This study represents the first demonstration of a repellent effect of ant chemical traces on spider mites. Considering the substantial abundance and global distribution of ants in nature, such repellent effects may help to answer the long-standing question of why only a small fraction of available plant resources is used by herbivores. Although spider mites have developed resistance against many synthetic pesticides, natural compounds that simulate ant chemical traces may repel spider mites from agricultural crops.

Gene expression of PLAT and ATS3 proteins increases plant resistance to insects.

MAIN CONCLUSION: Genes of the PLAT protein family, including PLAT and ATS3 subfamilies of higher plants and homologs of liverwort, are involved in plant defense against insects. Laticifer cells in plants contain large amounts of anti-microbe or anti-insect proteins and are involved in plant defense against biotic stresses. We previously found that PLAT proteins accumulate in laticifers of fig tree (Ficus carica) at comparable levels to those of chitinases, and the transcript level of ATS3, another PLAT domain-containing protein, is highest in the transcriptome of laticifers of Euphorbia tirucalli. In this study, we investigated whether the PLAT domain-containing proteins are involved in defense against insects. Larvae of the lepidopteran Spodoptera litura showed retarded growth when fed with Nicotiana benthamiana leaves expressing F. carica PLAT or E. tirucalli ATS3 genes, introduced by agroinfiltration using expression vector pBYR2HS. Transcriptome analysis of these leaves indicated that ethylene and jasmonate signaling were activated, leading to increased expression of genes for PR-1, ß-1,3-glucanase, PR5 and trypsin inhibitors, suggesting an indirect mechanism of PLAT- and ATS3-induced resistance in the host plant. Direct cytotoxicity of PLAT and ATS3 to insects was also possible because heterologous expression of the corresponding genes in Drosophila melanogaster caused apoptosis-mediated cell death in this insect. Larval growth retardation of S. litura occurred when they were fed radish sprouts, a good host for agroinfiltration, expressing any of nine homologous genes of dicotyledon Arabidopsis thaliana, monocotyledon Brachypodium distachyon, conifer Picea sitchensis and liverwort Marchantia polymorpha. Of these nine genes, the heterologous expression of A. thaliana AT5G62200 and AT5G62210 caused significant increases in larval death. These results indicated that the PLAT protein family has largely conserved anti-insect activity in the plant kingdom (249 words).

Contact Sex Pheromone Activity of Synthetic Gomadalactones in Male White-Spotted Longhorn Beetle, Anoplophora malasiaca (Coleoptera: Cerambycidae).

The elytra of females of the white-spotted longhorn beetle, Anoplophora malasiaca (Coleoptera: Cerambycidae), are coated with a contact sex pheromone, which was previously shown to be composed of at least three chemical groups. Individually, the chemical groups had little pheromonal activity, but a blend of all three exhibited activity equal to that of the crude female extract. Two groups are female-specific aliphatic hydrocarbons and ketones, which were previously synthesized and confirmed to elicit mating behavior. The third group consists of three lactones, gomadalactones A, B, and C, whose chemical structures were previously identified. These have now been synthesized, and the contact sex pheromone activities of synthetic gomadalactones A, B, and C, and the diastereomer of gomadalactone C, were tested in bioassays in this study. When tested in combination with synthetic hydrocarbons and ketones at the same doses as found in female elytra extract, the individual gomadalactones and a blend showed potent pheromonal activity equivalent to that of the crude extract of the elytra of female beetles. This completes the identification of the essential components of the contact sex pheromone of A. malasiaca. Redundancy of components in the hydrocarbon and ketone groups required to elicit mating behavior was observed previously, and this was also true for the gomadalactones.

Olfactory Cues from Pathogenic Fungus Affect the Direction of Motion of Termites, Coptotermes formosanus.

Formosan subterranean termites, Coptotermes formosanus, tend to avoid pathogen odors when tested in Y-tube olfactometers, but approach and groom exposed nestmates to remove pathogens from their cuticle and maintain a healthy population. To better understand their differential reaction to pathogens and their odors, the relationship between odor cues and direction of motion was examined with the fungus Isaria fumosorosea K3 strain. The results indicate that nestmate odor was strongly attractive only in tests where fungal odors were present in both branches of the olfactometer. Termites generally avoid fungal odors when offered a choice without fungal odor. We also tested termite aversion to 3-octanone and 1-octen-3-ol, major surface chemical compounds of I. fumosorosea K3, and estimated the total mass of these compounds present on the conidial surface by direct extraction method. The total quantity of these chemicals on the surface of fungal conidia was estimated to be approximately 0.01 ng per 10(7) conidia. This study demonstrates a context dependent behavioral change in termites in response to the odors of pathogenic fungi.

"Double-trick" visual and chemical mimicry by the juvenile orchid mantis hymenopus coronatus used in predation of the oriental honeybee apis cerana.

It has long been hypothesized that the flower-like appearance of the juvenile orchid mantis is used as visual camouflage to capture flower-visiting insects, although it is doubtful whether such morphological resemblance alone could increase their success in hunting. We confirmed that juvenile female orchid mantes often succeed in capturing oriental honeybees, while adult females often fail. Since most of the honeybees approached the juveniles from the front, we hypothesized that juvenile orchid mantes might attract honeybees by emitting some volatile chemical cues. Gas chromatography-mass spectrometry analyses revealed that the mantes' mandibular adducts contained 3-hydroxyoctanoic acid (3HOA) and 10-hydroxy-(E)-2-decenoic acid (10HDA), both of which are also features of the pheromone communication of the oriental honeybee. We also successfully detected 3HOA emitted in the head space air only at the time when the juvenile mantes were attempting to capture their prey. Field bioassay showed that the Oriental Honeybee predominantly preferred to visit dummies impregnated with a mixture of the appropriate amounts and ratios of 3HOA and 10HDA. We therefore conclude that the juvenile mantes utilize these as allelochemicals to trick and attract oriental honeybees.

Chemical investigation of aggregation behaviour in the two-spotted spider mite Tetranychus urticae.

The silk produced by the group-living mite Tetranychus urticae provides group protection and is used as an informative material during habitat settlement, egg laying, mating, and dispersal events. In this context, cues contained in the silk and other materials produced by mites [eggs, black faeces (BF) and white faeces + silk (WFS)] were investigated. Chemical compounds were extracted by hexane or methanol, and choice tests were used to determine the individual attractiveness of each extract. For both solvents, individuals did not respond to the extract from eggs and WFS. BF extracts were attractive for both solvents. After separating the BF methanol extract into four different chemical components using thin layer chromatography, no component was determined to be responsible for mite attraction. This work supports the evidence that the faeces of T. urticae do contain substances that promote behavioural changes. Not particular chemical compounds but combinations of them seem to induce the mites' preference. Moreover, the response of mites to chemicals seemed to be context dependent as mites belonging to populations with different densities differed in their attraction to BF extracts.

Spider mites avoid caterpillar traces to prevent intraguild predation.

The phytophagous spider mites Tetranychus kanzawai and Tetranychus urticae can be as small as < 0.5 mm; thus, they are often incidentally consumed along with food plant leaves by voracious lepidopteran larvae (hereafter, 'caterpillars'). Therefore, the ability to avoid such intraguild predation should confer a selective advantage to mites. We experimentally demonstrated that adult females of both mite species avoided settling on food plant leaves with traces of all tested caterpillar species (Bombyx mori, Papilio xuthus, Spodoptera litura and Theretra oldenlandiae). We examined additional interactions using B. mori and T. kanzawai and found that B. mori trace avoidance by T. kanzawai lasted for more than 48 h. Tetranychus kanzawai also avoided B. mori traces on plant stems, along which mites access leaves. Moreover, T. kanzawai avoided acetone extracts of B. mori traces applied to filter paper, indicating that chemical substances of caterpillar traces are responsible for the avoidance. This study is the first demonstration of a repellent effect of herbivore trace chemicals on heterospecific herbivores. Although spider mites have developed resistance against many synthetic pesticides, these results predict that natural compounds simulating caterpillar traces may repel spider mites from agricultural crops.

Chemical identification and ethological function of soldier-specific secretion in Japanese subterranean termite Reticulitermes speratus (Rhinotermitidae).

We identified the soldier-specific compounds in the Japanese subterranean termite, Reticulitermes speratus, to clarify their ethological roles. Silica gel column chromatography separated one major soldier-specific compound in the hexane fraction accounting for 70-80% of the total amount of the fraction, while cuticular hydrocarbons constituted the rest. We identified the compound as ß-selinene by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy. Comparative GC analyses of the major exocrine glands detected the compound in the soldier's frontal gland. Both soldiers and workers made aggregation to the hexane fraction, as well as to the crushed heads and head extract of the soldiers. They did not aggregate to cuticular hydrocarbons, making it likely that ß-selinene was the aggregation pheromone in this species. The opportunistic predator of this termite, Lasius japonicus, was also attracted to the compounds. The ant workers, therefore, would use the termite aggregation pheromone as a kairomone for hunting them.

Musty odor of entomopathogens enhances disease-prevention behaviors in the termite Coptotermes formosanus.

Termites often eliminate pathogens directly through mutual grooming, and are thereby prevent infections from entomopathogenic fungi. Our previous study confirmed that the antennae of Coptotermesformosanus sensitively responded to the musty odor of entomopathogenic fungi. However, it is unclear if this odor has any effect on termite behavior. The purpose of this study was to clarify the effects of fungal odor on termite behavior, especially on conidia removal. The musty odor was prepared as an aqueous solution by immersing conidia in distilled water. When untreated termites were mixed with fungal-odor-treated termites at a ratio of 4:1, mutual grooming and attack of treated termites were frequently observed. This indicated that the fungal odor triggered these behavioral responses. While some components of the fungal odor were found in all of the entomopathogenic fungi tested, the odor profiles differed among the isolates.

Behavioral changes in the termite, Coptotermes formosanus (Isoptera), inoculated with six fungal isolates.

The studies of pathogen-prevention behaviors of termites have focused on hygiene behavior directed only against highly virulent pathogens. Therefore, we compared behavioral changes in the subterranean termite Coptotermes formosanus following contact with entomopathogenic fungi with different levels of virulence. The fungal virulence was inferred from the daily mortality and the LD50 value in previous data. When untreated termites were allowed to contact their fungus-inoculated nestmates, mutual grooming was frequent during 30 min after inoculation. The inoculated termites were often attacked and eaten by their uninoculated nestmates, and then buried after death. Notably, there was no influence of fungal virulence on these pathogen-prevention behaviors. However, the fungal isolates and genera affected not only the frequency of the behaviors but also the horizontal transmission pattern, the number of dead individuals and the survival period before the first death following infection.

Chemical identification of an aggregation pheromone in the termite Reticulitermes speratus.

Social behaviours in termites are regulated by sophisticated chemical communication systems. The majority of subterranean termites continuously forage for new wood resources to expand their nesting areas; an aggregation pheromone is presumed to regulate this process. However, the chemical components of this pheromone have never been determined. We identified the chemical properties of the aggregation pheromone that signals nestmate presence and induces arrest in the termite Reticulitermes speratus. The results of gas chromatography-mass spectrometry analyses and bioassays indicated that R. speratus worker release the pheromone to their nesting site. The pheromone consists of an aromatic compound (2-phenylundecane), cuticular hydrocarbons (pentacosane and heptacosane), fatty acids (palmitic acid and trans-vaccenic acid), and cholesterol; the pheromone induces long-term aggregation at new nesting and feeding sites. Although 2-phenylundecane alone attracted workers, the combination of all six compounds showed greater arrestant activity than 2-phenylundecane alone. This suggests that 2-phenylundecane functions as an attractant, whereas the remaining five components function as arrestants. Our results indicate that foraging worker termites produce a multi-component aggregation pheromone by combining a volatile hydrocarbon and non-volatile lipids with cuticular hydrocarbons. This pheromone enables rapid, long-lasting aggregation of termite workers, which contributes to efficient feeding and colonisation of new wood. Our work furthers the understanding of chemical communication systems underlying social assembly in social insects.

Chemical disguise as particular caste of host ants in the ant inquiline parasite Niphanda fusca (Lepidoptera: Lycaenidae).

The exploitation of parental care is common in avian and insect 'cuckoos' and these species engage in a coevolutionary arms race. Caterpillars of the lycaenid butterfly Niphanda fusca develop as parasites inside the nests of host ants (Camponotus japonicus) where they grow by feeding on the worker trophallaxis. We hypothesized that N. fusca caterpillars chemically mimic host larvae, or some particular castes of the host ant, so that the caterpillars are accepted and cared for by the host workers. Behaviourally, it was observed that the host workers enthusiastically tended glass dummies coated with the cuticular chemicals of larvae or males and those of N. fusca caterpillars living together. Cuticular chemical analyses revealed that N. fusca caterpillars grown in a host ant nest acquired a colony-specific blend of cuticular hydrocarbons (CHCs). Furthermore, the CHC profiles of the N. fusca caterpillars were particularly close to those of the males rather than those of the host larvae and the others. We suggest that N. fusca caterpillars exploit worker care by matching their cuticular profile to that of the host males, since the males are fed by trophallaxis with workers in their natal nests for approximately ten months.

Varied Effects of Tending Ant Species on the Development of Facultatively Myrmecophilous Lycaenid Butterfly Larvae.

Ants often tend and protect the larvae of various myrmecophilous lycaenid species, which influences the fitness of butterflies by altering their growth and developmental time. Tending produces diverse effects depending on lycaenid sex and the lycaenid/ant species combination. Effects are widely variable, especially in facultatively myrmecophilous lycaenids such as Plebejus argyrognomon praeterinsularis, because they are associated with several ant species and can survive without any ant tending. We studied the effects of ant tending on the adult body mass and larval developmental time of P. argyrognomon praeterinsularis. Female larvae grew significantly heavier as adults when tended by Camponotus japonicus rather than by either Lasius japonicus or no ant species. Ant tending did not affect the body mass of adult males or the developmental time of either male or female larvae. Thus, tending by C. japonicus could increase the fitness of P. argyrognomon praeterinsularis by increasing the mass of females without prolonging the duration of vulnerable immature stages, because larger females generally lay more eggs. This means that even facultatively myrmecophilous lycaenids might gain fitness benefits from particular ant species, which could be important in the conservation and management of at-risk species of facultatively myrmecophilous lycaenids.

A DNA and morphology based phylogenetic framework of the ant genus Lasius with hypotheses for the evolution of social parasitism and fungiculture.

BACKGROUND: Ants of the genus Lasius are ecologically important and an important system for evolutionary research. Progress in evolutionary research has been hindered by the lack of a well-founded phylogeny of the subgenera, with three previous attempts disagreeing. Here we employed two mitochondrial genes (cytochrome c oxidase subunit I, 16S ribosomal RNA), comprising 1,265 bp, together with 64 morphological characters, to recover the phylogeny of Lasius by Bayesian and Maximum Parsimony inference after exploration of potential causes of phylogenetic distortion. We use the resulting framework to infer evolutionary pathways for social parasitism and fungiculture. RESULTS: We recovered two well supported major lineages. One includes Acanthomyops, Austrolasius, Chthonolasius, and Lasius pallitarsis, which we confirm to represent a seventh subgenus, the other clade contains Dendrolasius, and Lasius sensu stricto. The subgenus Cautolasius, displaying neither social parasitism nor fungiculture, probably belongs to the second clade, but its phylogenetic position is not resolved at the cutoff values of node support we apply. Possible causes for previous problems with reconstructing the Lasius phylogeny include use of other reconstruction techniques, possibly more prone to instabilities in some instances, and the inclusion of phylogenetically distorting characters. CONCLUSION: By establishing an updated phylogenetic framework, our study provides the basis for a later formal taxonomic revision of subgenera and for studying the evolution of various ecologically and sociobiologically relevant traits of Lasius, although there is need for future studies to include nuclear genes and additional samples from the Nearctic. Both social parasitism and fungiculture evolved twice in Lasius, once in each major lineage, which opens up new opportunities for comparative analyses. The repeated evolution of social parasitism has been established for other groups of ants, though not for temporary social parasitism as found in Lasius. For fungiculture, the independent emergence twice in a monophyletic group marks a novel scenario in ants. We present alternative hypotheses for the evolution of both traits, with one of each involving loss of the trait. Though less likely for both traits than later evolution without reversal, we consider reversal as sufficiently plausible to merit independent testing.

Trans 18-carbon monoenoic fatty acid has distinct effects from its isomeric cis fatty acid on lipotoxicity and gene expression in Saccharomyces cerevisiae.

Epidemiological studies have suggested that an excess intake of trans-unsaturated fatty acids increases the risk of coronary heart disease. However, the mechanisms of action of trans-unsaturated fatty acids in eukaryotic cells remain unclear. Since the budding yeast Saccharomyces cerevisiae can grow using fatty acids as the sole carbon source, it is a simple and suitable model organism for understanding the effects of trans-unsaturated fatty acids at the molecular and cellular levels. In this study, we compared the physiological effects of Δ9 cis and trans 18-carbon monoenoic fatty acids (oleic acid and elaidic acid) in yeast cells. The results obtained revealed that the two types have distinct effects on the expression of OLE1, which encodes Δ9 desaturase, and lipotoxicity in are1Δare2Δdga1Δlro1Δ and gat1Δ cells. Our results suggest that cis and trans 18-carbon monoenoic fatty acids exert different physiological effects in the regulation of gene expression and processing of excess fatty acids in yeast.

Intraspecific variation of cuticular hydrocarbon composition in Formica japonica Motschoulsky (Hymenoptera: Formicidae).

Cuticular hydrocarbons and morphological features were compared among 80 Formica japonica colonies collected in Japan. Although a few morphological differences were found in workers among the colonies, four different types of cuticular hydrocarbon composition were observed. This was supported by a principal component analysis. We further compared the cuticular hydrocarbons among a total of approximately 400 F. japonica colonies, and categorized the hydrocarbon components into four types based on the result of discriminant analyses for the first 80 colonies. Type 1 was observed in colonies mainly collected in southern Honshu, Shikoku, and Kyushu. Types 2, 3, and 4 were from colonies with primary collections in Southern Honshu, central and Pacific coast northern Honshu, and the Sea of Japan coasts of northern Honshu and Hokkaido, respectively. The occurrence of four distinct types of CHC composition suggests that the colonies that produce them are separate species.

Ants use partner specific odors to learn to recognize a mutualistic partner.

Regulation via interspecific communication is an important for the maintenance of many mutualisms. However, mechanisms underlying the evolution of partner communication are poorly understood for many mutualisms. Here we show, in an ant-lycaenid butterfly mutualism, that attendant ants selectively learn to recognize and interact cooperatively with a partner. Workers of the ant Pristomyrmex punctatus learn to associate cuticular hydrocarbons of mutualistic Narathura japonica caterpillars with food rewards and, as a result, are more likely to tend the caterpillars. However, the workers do not learn to associate the cuticular hydrocarbons of caterpillars of a non-ant-associated lycaenid, Lycaena phlaeas, with artificial food rewards. Chemical analysis revealed cuticular hydrocarbon profiles of the mutualistic caterpillars were complex compared with those of non-ant-associated caterpillars. Our results suggest that partner-recognition based on partner-specific chemical signals and cognitive abilities of workers are important mechanisms underlying the evolution and maintenance of mutualism with ants.

Odor aversion and pathogen-removal efficiency in grooming behavior of the termite Coptotermes formosanus.

The results of biocontrol with entomopathogens in termites have been discouraging because of the strong social hygiene behavior for removing pathogens from termite colonies. However, the mechanism of pathogen detection is still unclear. For the successful application of biopesticides to termites in nature, it would be beneficial to identify substances that could disrupt the termite's ability to perceive pathogens. We hypothesized that termites can perceive pathogens and this ability plays an important role in effective hygiene behavior. In this study, pathogen-detection in the subterranean termite Coptotermes formosanus was investigated. We performed quantitative assays on conidia removal by grooming behavior using epifluoresence microscopy and Y-maze tests to examine the perception of fungal odor by termites. Three species each of high- and low-virulence entomopathogenic fungi were used in each test. The results demonstrated that termites removed conidia more effectively from a nestmate's cuticle if its odor elicited stronger aversion. Highly virulent pathogens showed higher attachment rates to termite surfaces and their odors were more strongly avoided than those of low-virulence isolates in the same species. Moreover, termites appeared to groom each other more persistently when they had more conidia on their bodies. In brief, insect perception of pathogen-related odor seems to play a role in the mechanism of their hygiene behavior.