Structural and wetting properties of nature\u27s finest silks (order Embioptera)

Insects from the order Embioptera (webspinners) spin silk fibres which are less than 200 nm in diameter. In this work, we characterized and compared the diameters of single silk fibres from nine species—Antipaluria urichi, Pararhagadochir trinitatis, Saussurembia calypso, Diradius vandykei, Aposthonia ceylonica, Haploembia solieri, H. tarsalis, Oligotoma nigra and O. saundersii. Silk from seven of these species have not been previously quantified. Our studies cover five of the 10 named taxonomic families and represent about one third of the known taxonomic family-level diversity in the order Embioptera. Naturally spun silk varied in diameter from 43.6 ± 1.7 nm for D. vandykei to 122.4 ± 3.2 nm for An. urichi. Mean fibre diameter did not correlate with adult female body length. Fibre diameter is more similar in closely related species than in more distantly related species. Field observations indicated that silk appears shiny and smooth when exposed to rainwater. We therefore measured contact angles to learn more about interactions between silk and water. Higher contact angles were measured for silks with wider fibre diameter and higher quantity of hydrophobic amino acids. High static contact angles (ranging up to 122° ± 3° for An. urichi) indicated that silken sheets spun by four arboreal, webspinner species were hydrophobic. A second contact angle measurement made on a previously wetted patch of silk resulted in a lower contact angle (average difference was greater than 27°) for all four species. Our studies suggest that silk fibres which had been previously exposed to water exhibited irreversible changes in hydrophobicity and water adhesion properties. Our results are in alignment with the ‘super-pinning’ site hypothesis by Yarger and co-workers to describe the hydrophobic, yet water adhesive, properties exhibited by webspinner silk fibres. The physical and chemical insights gained here may inform the synthesis and development of smaller diameter silk fibres with unique water adhesion properties

From ground pools to treeholes: convergent evolution of habitat and phenotype in Aedes mosquitoes

Abstract Background Invasive mosquito species are responsible for millions of vector-borne disease cases annually. The global invasive success of Aedes mosquitoes such as Aedes aegypti and Aedes albopictus has relied on the human transport of immature stages in container habitats. However, despite the importance of these mosquitoes and this ecological specialization to their widespread dispersal, evolution of habitat specialization in this group has remained largely unstudied. We use comparative methods to evaluate the evolution of habitat specialization and its potential influence on larval morphology, and evaluate whether container dwelling and invasiveness are monophyletic in Aedes. Results We show that habitat specialization has evolved repeatedly from ancestral ground pool usage to specialization in container habitats. Furthermore, we find that larval morphological scores are significantly associated with larval habitat when accounting for evolutionary relationships. We find that Ornstein-Uhleinbeck models with unique optima for each larval habitat type are preferred over several other models based predominantly on neutral processes, and that OU models can reliably simulate real morphological data. Conclusions Our results demonstrate that multiple lineages of Aedes have convergently evolved a key trait associated with invasive success: the use of container habitats for immature stages. Moreover, our results demonstrate convergence in morphological characteristics as well, and suggest a role of adaptation to habitat specialization in driving phenotypic diversity in this mosquito lineage. Finally, our results highlight that the genus Aedes is not monophyletic

The mean wing length of female and male mosquitoes exposed to different parasite dosages.

<p>Both female and male mosquitoes show smaller body size when parasitized, but the relative effect for female <i>Ae</i>. <i>albopictus</i> appears greater, as evidenced by the interaction between sex and dosage (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184573#pone.0184573.t002" target="_blank">Table 2</a>). Whiskers are bootstrapped 95% confidence intervals (1000 replicates); no confidence intervals for any points overlap.</p

Two approximations of mean parasite per capita growth rate under different parasite doses to mosquito hosts.

<p>Parasite growth rate declined significantly regardless of which growth rate type, including oocysts from the male mosquito (r_p) or not including them (r_m) was used, suggesting an effect of density on parasite growth. Colored letters correspond to separate Tukey’s HSD tests on ANOVA models of each growth rate approximation. Whiskers are bootstrapped 95% confidence intervals (1000 replicates). Mean points are dodged for visibility.</p

The mean total oocysts produced by mosquitoes exposed to different parasite dosages.

<p>Oocyst production within microcosms increases with dosage of parasite. Total oocysts produced did not significantly vary with sex (Table C in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184573#pone.0184573.s003" target="_blank">S1 File</a>). Both sexes received equal doses; mean values are ‘dodged’ at each parasite dosage for visibility. Whiskers are bootstrapped 95% confidence intervals (1000 replicates).</p

Population genomics of Culiseta melanura, the principal vector of Eastern equine encephalitis virus in the United States.

BACKGROUND:Eastern Equine Encephalitis (EEE) (Togaviridae, Alphavirus) is a highly pathogenic mosquito-borne arbovirus that circulates in an enzootic cycle involving Culiseta melanura mosquitoes and wild Passeriformes birds in freshwater swamp habitats. Recently, the northeastern United States has experienced an intensification of virus activity with increased human involvement and northward expansion into new regions. In addition to its principal role in enzootic transmission of EEE virus among avian hosts, recent studies on the blood-feeding behavior of Cs. melanura throughout its geographic range suggest that this mosquito may also be involved in epizootic / epidemic transmission to equines and humans in certain locales. Variations in blood feeding behavior may be a function of host availability, environmental factors, and/or underlying genetic differences among regional populations. Despite the importance of Cs. melanura in transmission and maintenance of EEE virus, the genetics of this species remains largely unexplored. METHODOLOGY AND PRINCIPLE FINDINGS:To investigate the occurrence of genetic variation in Cs. melanura, the genome of this mosquito vector was sequenced resulting in a draft genome assembly of 1.28 gigabases with a contig N50 of 93.36 kilobases. Populations of Cs. melanura from 10 EEE virus foci in the eastern North America were genotyped with double-digest RAD-seq. Following alignment of reads to the reference genome, variant calling, and filtering, 40,384 SNPs were retained for downstream analyses. Subsequent analyses revealed genetic differentiation between northern and southern populations of this mosquito species. Moreover, limited fine-scale population structure was detected throughout northeastern North America, suggesting local differentiation of populations but also a history of ancestral polymorphism or contemporary gene flow. Additionally, a genetically distinct cluster was identified predominantly at two northern sites. CONCLUSION AND SIGNIFICANCE:This study elucidates the first evidence of fine-scale population structure in Cs. melanura throughout its eastern range and detects evidence of gene flow between populations in northeastern North America. This investigation provides the groundwork for examining the consequences of genetic variations in the populations of this mosquito species that could influence vector-host interactions and the risk of human and equine infection with EEE virus

ANCOVA results for the response variable percentage of oocysts in the adult and the explanatory variables of sex and parasite dosage, with covariates of wing length and time to emergence, and a random effect for microcosm.

<p>ANCOVA results for the response variable percentage of oocysts in the adult and the explanatory variables of sex and parasite dosage, with covariates of wing length and time to emergence, and a random effect for microcosm.</p

Differential response to mosquito host sex and parasite dosage suggest mixed dispersal strategies in the parasite <i>Ascogregarina taiwanensis</i> - Fig 1

<p>The mean proportion of mosquitoes surviving to adulthood (A) and mosquito per capita rate of increase (B) exposed to different parasite dosages. Host <i>Aedes albopictus</i> fitness declines by two measures as dosage of <i>Ascogregarina taiwanensis</i> increases. Different letters within each plot are significantly different based on Tukey’s HSD. Whiskers are bootstrapped 95% confidence intervals (1000 replicates).</p

The percent of oocysts in the adult mosquito at three parasite dosages.

<p>Male mosquitoes had a smaller proportion of oocysts in the adult until the highest dosage, 10000 oocysts/ml, where male and female mosquitoes had the same percent of oocysts in adults. Different letters correspond to separate Tukey’s HSD tests on the ANCOVA model. Whiskers are bootstrapped 95% confidence intervals (1000 replicates). Mean points are dodged for visibility.</p

Summary of partial ANOVA results for the explanatory variable of parasite dosage and some response variables^**.

<p>Summary of partial ANOVA results for the explanatory variable of parasite dosage and some response variables^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184573#t001fn002" target="_blank">**</a>}.</p