Characterization and Generation of Male Courtship Song in Cotesia congregata (Hymenoptera: Braconidae)

Background Male parasitic wasps attract females with a courtship song produced by rapid wing fanning. Songs have been described for several parasitic wasp species; however, beyond association with wing fanning, the mechanism of sound generation has not been examined. We characterized the male courtship song of Cotesia congregata (Hymenoptera: Braconidae) and investigated the biomechanics of sound production. Methods and Principal Findings Courtship songs were recorded using high-speed videography (2,000 fps) and audio recordings. The song consists of a long duration amplitude-modulated “buzz” followed by a series of pulsatile higher amplitude “boings,” each decaying into a terminal buzz followed by a short inter-boing pause while wings are stationary. Boings have higher amplitude and lower frequency than buzz components. The lower frequency of the boing sound is due to greater wing displacement. The power spectrum is a harmonic series dominated by wing repetition rate ~220 Hz, but the sound waveform indicates a higher frequency resonance ~5 kHz. Sound is not generated by the wings contacting each other, the substrate, or the abdomen. The abdomen is elevated during the first several wing cycles of the boing, but its position is unrelated to sound amplitude. Unlike most sounds generated by volume velocity, the boing is generated at the termination of the wing down stroke when displacement is maximal and wing velocity is zero. Calculation indicates a low Reynolds number of ~1000. Conclusions and Significance Acoustic pressure is proportional to velocity for typical sound sources. Our finding that the boing sound was generated at maximal wing displacement coincident with cessation of wing motion indicates that it is caused by acceleration of the wing tips, consistent with a dipole source. The low Reynolds number requires a high wing flap rate for flight and predisposes wings of small insects for sound production

Rapid Dissemination of SIV Follows Multisite Entry after Rectal Inoculation

Receptive ano-rectal intercourse is a major cause of HIV infection in men having sex with men and in heterosexuals. Current knowledge of the mechanisms of entry and dissemination during HIV rectal transmission is scarce and does not allow the development of preventive strategies. We investigated the early steps of rectal infection in rhesus macaques inoculated with the pathogenic isolate SIVmac251 and necropsied four hours to nine days later. All macaques were positive for SIV. Control macaques inoculated with heat-inactivated virus were consistently negative for SIV. SIV DNA was detected in the rectum as early as four hours post infection by nested PCR for gag in many laser-microdissected samples of lymphoid aggregates and lamina propria but never in follicle-associated epithelium. Scarce SIV antigen positive cells were observed by immunohistofluorescence in the rectum, among intraepithelial and lamina propria cells as well as in clusters in lymphoid aggregates, four hours post infection and onwards. These cells were T cells and non-T cells that were not epithelial cells, CD68+ macrophages, DC-SIGN+ cells or fascin+ dendritic cells. DC-SIGN+ cells carried infectious virus. Detection of Env singly spliced mRNA in the mucosa by nested RT-PCR indicated ongoing viral replication. Strikingly, four hours post infection colic lymph nodes were also infected in all macaques as either SIV DNA or infectious virus was recovered. Rapid SIV entry and dissemination is consistent with trans-epithelial transport. Virions appear to cross the follicle-associated epithelium, and also the digestive epithelium. Viral replication could however be more efficient in lymphoid aggregates. The initial sequence of events differs from both vaginal and oral infections, which implies that prevention strategies for rectal transmission will have to be specific. Microbicides will need to protect both digestive and follicle-associated epithelia. Vaccines will need to induce immunity in lymph nodes as well as in the rectum

EVOLUTION DES ONISCIDEA (CRUSTACEA, ISOPODA) (ANALYSE DE GENES MITOCHONDRIAUX ET IMPLICATIONS PHYLOGENETIQUES)

LE SOUS-ORDRE DES ONISCIDEA (ISOPODA) EST LE SEUL GROUPE DE CRUSTACES QUI COMPORTE EN GRANDE MAJORITE DES ESPECES ADAPTEES A LA VIE TERRESTRE, COMPTANT PRES DE 4000 ESPECES REPARTIES DANS LE MONDE ENTIER. CEPENDANT, LE PASSAGE DE CES CRUSTACES D'UN ENVIRONNEMENT AQUATIQUE A UN ENVIRONNEMENT TERRESTRE RESTE ENIGMATIQUE. EN EFFET, LES RELATIONS DE PARENTE ENTRE LES ONISCIDES ET LES AUTRES SOUS-ORDRES D'ISOPODES ET LA MONOPHYLIE DE CE GROUPE RESTENT CONTROVERSES. MALGRE LES ESSORS RECENTS DES PHYLOGENIES MOLECULAIRES, SEULES DES PHYLOGENIES MORPHOLOGIQUES ONT ETE PROPOSEES CHEZ LES ISOPODES, AUCUNE ETUDE MOLECULAIRE N'AYANT ETE MENEE JUSQU'A PRESENT. POUR ABORDER LA PHYLOGENIE DES ONISCIDES, NOUS AVONS CHOISI DEUX MARQUEURS MITOCHONDRIAUX : L'ADN RIBOSOMIQUE 16S ET LA CYTOCHROME OXYDASE I. LES SEQUENCES PARTIELLES DES DEUX GENES SONT ETUDIEES SEPAREMENT, PUIS EN TOTAL EVIDENCE. CETTE ETUDE DE PHYLOGENIE CLASSIQUE EST COMPLETEE PAR L'ANALYSE DE L'EVOLUTION DES STRUCTURES SECONDAIRES PARTIELLES DES ARNR 16S CHEZ PLUSIEURS ISOPODES. LES DIVERGENCES ENTRE LES ISOPODES AQUATIQUES ET LES PLUS ANCIENS DES ISOPODES TERRESTRES SONT MAL RESOLUES, CE QUI EST EN FAVEUR D'UNE EMERGENCE RAPIDE DE CE GROUPE, SUIVIE D'UNE DIVERGENCE PLUS LENTE LORS DE LA DISPERSION DES ESPECES DANS LE MILIEU TERRESTRE. L'EVOLUTION MOLECULAIRE DES MARQUEURS UTILISES ET LES DONNEES PALEONTOLOGIQUES EXISTANTES SEMBLENT EN FAVEUR DE CETTE HYPOTHESE. D'AUTRE PART, LE GROUPE DES ONISCIDES PRESENTE UN INTERET SUPPLEMENTAIRE DU FAIT DE SON INFECTION PAR DES BACTERIES DU GENRE WOLBACHIA, PARASITES DE LA REPRODUCTION. LA VARIATION DES MARQUEURS MITOCHONDRIAUX EST EXAMINEE AUX NIVEAUX INTERSPECIFIQUE ET INTRASPECIFIQUE, ET REVELE L'EXISTENCE DE NOMBREUX TRANSFERTS DE BACTERIES ENTRE ESPECES ET AUSSI ENTRE POPULATIONS. L'ETUDE DES GENES MITOCHONDRIAUX DES ISOPODES TERRESTRES NOUS PERMET AINSI D'APPORTER DE NOUVELLES INFORMATIONS CONCERNANT L'EVOLUTION DES ISOPODES TERRESTRES ET LEURS RELATIONS AVEC LES WOLBACHIA.PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Wolbachia infection in crustaceans: novel hosts and potential routes for horizontal transmission

International audienc

Molecular Characterization and Evolution of Arthropod-Pathogenic Rickettsiella Bacteria▿

We determined the 16S rRNA gene sequences of three crustacean “Rickettsiella armadillidii” strains. Rickettsiella bacteria overall appear to form a monophyletic group that diverged from Coxiella bacteria ∼350 million years ago. Therefore, the genus Rickettsiella as a whole (not just Rickettsiella grylli) should be classified among the Gammaproteobacteria instead of the Alphaproteobacteria

How invasion by Ailanthus altissima transforms soil and litter communities in a temperate forest ecosystem

International audienceThe invasive tree Ailanthus altissima (Mill.) Swingle (tree of heaven) is considered as an ecosystem transformer, which alters plant communities in open areas and forests. Nothing is yet known about its potential effects on forest soil biota and ecosystem functioning. We present here the first study assessesing the impact of A. altissima on soil and litter invertebrate communities in a temperate forest. We analyzed the effect of varying A. altissima densities in a forest of north-eastern France on soil microbial activity, diversity of various litter and soil invertebrate groups (Arthropoda, Lumbricidae, Gastropoda), diversity of functional groups (predatory, detritivorous, coprophagous, phytophagous), and trophic structure. Our study shows that increasing density of A. altissima is associated to lower soil microbial activity, decreasing abundance of litter detritivores (Acari and Collembola) and aboveground predatory Coleoptera, and decreasing species richness of terrestrial Gastropoda. In contrast, increased A. altissima density corresponded with greater abundances of litter Lumbricidae and aboveground coprophagous Coleoptera. We found an overall impact of A. altissima invasion on the soil food web structure that could accelerate the mineralization of organic matter and potentially favor nitrophilous plant species in understory plant communities