Offspring allocation in structured populations with dimorphic males

Summary Many fig wasp species have dimorphic males. These males often mate in different localities; one typically disperses before mating whereas the other does not disperse. In 1979 a model was developed for offspring allocation in dimorphic fig wasps, but it assumed that females only lay a single egg per fig. This assumption is not realistic and precludes any effects local mate competition (LMC) may exert on morph abundance. I develop a model without these restrictions and show that the optimal proportions of each morph is determined by two parameters. Firstly, the proportion of the non-dispersing morph is affected by the mean number of females that oviposit in a patch. This effect is due to the negative correlation between LMC between brothers and the number of females that oviposit in a patch. Secondly, the proportions of both male morphs correlate with the expected proportion of females which will mate with each morph. The separation of the two parameters generalizes the model to any other species which is spatially structured and which has two male morphs or even two alternative mating strategies. A comparison of two models shows that parent—offspring conflict involving morph ratios will not have far reaching consequences. I test these models using the 1979 model's data and both models accurately predict the variation in morph ratios in six species of dimorphic fig wasps.     

Copper-Adapted Suillus luteus, a Symbiotic Solution for Pines Colonizing Cu Mine Spoils

Natural populations thriving in heavy-metal-contaminated ecosystems are often subjected to selective pressures for increased resistance to toxic metals. In the present study we describe a population of the ectomycorrhizal fungus Suillus luteus that colonized a toxic Cu mine spoil in Norway. We hypothesized that this population had developed adaptive Cu tolerance and was able to protect pine trees against Cu toxicity. We also tested for the existence of cotolerance to Cu and Zn in S. luteus. Isolates from Cu-polluted, Zn-polluted, and nonpolluted sites were grown in vitro on Cu- or Zn-supplemented medium. The Cu mine isolates exhibited high Cu tolerance, whereas the Zn-tolerant isolates were shown to be Cu sensitive, and vice versa. This indicates the evolution of metal-specific tolerance mechanisms is strongly triggered by the pollution in the local environment. Cotolerance does not occur in the S. luteus isolates studied. In a dose-response experiment, the Cu sensitivity of nonmycorrhizal Pinus sylvestris seedlings was compared to the sensitivity of mycorrhizal seedlings colonized either by a Cu-sensitive or Cu-tolerant S. luteus isolate. In nonmycorrhizal plants and plants colonized by the Cu-sensitive isolate, root growth and nutrient uptake were strongly inhibited under Cu stress conditions. In contrast, plants colonized by the Cu-tolerant isolate were hardly affected. The Cu-adapted S. luteus isolate provided excellent insurance against Cu toxicity in pine seedlings exposed to elevated Cu levels. Such a metal-adapted Suillus-Pinus combination might be suitable for large-scale land reclamation at phytotoxic metalliferous and industrial sites.     

Improving performance of Cytisus striatus on substrates contaminated with hexachlorocyclohexane (HCH) isomers using bacterial inoculants: developing a phytoremediation strategy

Background and aims

Microbe-assisted phytoremediation is particularly effective for organic pollutants. The leguminous shrub Cytisus striatus (Hill) Rothm. has been proposed as a candidate species for the rhizoremediation of hexachlorocyclohexane (HCH)-contaminated sites. The aim of this study was to improve the performance of this species using microbial inoculants.

Methods

C. striatus was grown in substrates contaminated with 0, 10 and 35 mg HCH kg^?1 for 8 weeks. Plants were either not inoculated (NI), or inoculated with the endophyte Rhodococcus erythropolis ET54b and the HCH-degrader Sphingomonas sp. D4 (isolated from a HCH-contaminated soil) on their own or in combination (ET, D4 and ETD4).

Results

Inoculation with both bacterial strains (ETD4) resulted in decreased HCH phytotoxicity and improved plant growth. HCH-exposed plants inoculated with ETD4 presented a 120–160 % increase in root, and 140–160 % increase in shoot biomass, and led to a decrease in the activities of enzymes involved in anti-oxidative defence. APOD activity was reduced by up to 37 % in shoot tissues and 25 % in root tissues, and corresponding activities of SOD were reduced by up to 35 % and 30 %. HCH dissipation was enhanced in the presence of C. striatus but no significant effect of microbial inoculants was observed.

Conclusions

Inoculating C. striatus with this combination of bacterial strains is a promising approach for the remediation of HCH-contaminated sites.     

The Effect of Three-Monthly Albendazole Treatment on Malarial Parasitemia and Allergy: A Household-Based Cluster-Randomized,Double-Blind,Placebo-Controlled Trial

Background

Helminth infections are proposed to have immunomodulatory activities affecting health outcomes either detrimentally or beneficially. We evaluated the effects of albendazole treatment, every three months for 21 months, on STH, malarial parasitemia and allergy.

Methods and Findings

A household-based cluster-randomized, double-blind, placebo-controlled trial was conducted in an area in Indonesia endemic for STH. Using computer-aided block randomization, 481 households (2022 subjects) and 473 households (1982 subjects) were assigned to receive placebo and albendazole, respectively, every three months. The treatment code was concealed from trial investigators and participants. Malarial parasitemia and malaria-like symptoms were assessed in participants older than four years of age while skin prick test (SPT) to allergens as well as reported symptoms of allergy in children aged 5–15 years. The general impact of treatment on STH prevalence and body mass index (BMI) was evaluated. Primary outcomes were prevalence of malarial parasitemia and SPT to any allergen. Analysis was by intention to treat. At 9 and 21 months post-treatment 80.8% and 80.1% of the study subjects were retained, respectively. The intensive treatment regiment resulted in a reduction in the prevalence of STH by 48% in albendazole and 9% in placebo group. Albendazole treatment led to a transient increase in malarial parasitemia at 6 months post treatment (OR 4.16(1.35–12.80)) and no statistically significant increase in SPT reactivity (OR 1.18(0.74–1.86) at 9 months or 1.37 (0.93–2.01) 21 months). No effect of anthelminthic treatment was found on BMI, reported malaria-like- and allergy symptoms. No adverse effects were reported.

Conclusions

The study indicates that intensive community treatment of 3 monthly albendazole administration for 21 months over two years leads to a reduction in STH. This degree of reduction appears safe without any increased risk of malaria or allergies.

Trial Registration

Controlled-Trials.com ISRCTN83830814     

Infection with Soil-Transmitted Helminths Is Associated with Increased Insulin Sensitivity

Objective

Given that helminth infections have been shown to improve insulin sensitivity in animal studies, which may be explained by beneficial effects on energy balance or by a shift in the immune system to an anti-inflammatory profile, we investigated whether soil-transmitted helminth (STH)-infected subjects are more insulin sensitive than STH-uninfected subjects.

Design

We performed a cross-sectional study on Flores island, Indonesia, an area with high prevalence of STH infections.

Methods

From 646 adults, stool samples were screened for Trichuris trichiura by microscopy and for Ascaris lumbricoides, Necator americanus, Ancylostoma duodenale, and Strongyloides stercoralis by qPCR. No other helminth was found. We collected data on body mass index (BMI, kg/m²), waist-to-hip ratio (WHR), fasting blood glucose (FBG, mmol/L), insulin (pmol/L), high sensitive C-reactive protein (ng/ml) and Immunoglobulin E (IU/ml). The homeostatic model assessment for insulin resistance (HOMAIR) was calculated and regression models were used to assess the association between STH infection status and insulin resistance.

Results

424 (66%) participants had at least one STH infection. STH infected participants had lower BMI (23.2 vs 22.5 kg/m², p value = 0.03) and lower HOMAIR (0.97 vs 0.81, p value = 0.05). In an age-, sex- and BMI-adjusted model a significant association was seen between the number of infections and HOMAIR: for every additional infection with STH species, the HOMAIR decreased by 0.10 (p for linear trend 0.01). This effect was mainly accounted for by a decrease in insulin of 4.9 pmol/L for every infection (p for trend = 0.07).

Conclusion

STH infections are associated with a modest improvement of insulin sensitivity, which is not accounted for by STH effects on BMI alone.     

3D Topography of the Young Adult Anal Sphincter Complex Reconstructed from Undeformed Serial Anatomical Sections

Background

Pelvic-floor anatomy is usually studied by artifact-prone dissection or imaging, which requires prior anatomical knowledge. We used the serial-section approach to settle contentious issues and an interactive 3D-pdf to make the results widely accessible.

Method

3D reconstructions of undeformed thin serial anatomical sections of 4 females and 2 males (21–35y) of the Chinese Visible Human database.

Findings

Based on tendinous septa and muscle-fiber orientation as segmentation guides, the anal-sphincter complex (ASC) comprised the subcutaneous external anal sphincter (EAS) and the U-shaped puborectal muscle, a part of the levator ani muscle (LAM). The anococcygeal ligament fixed the EAS to the coccygeal bone. The puborectal-muscle loops, which define the levator hiatus, passed around the anorectal junction and inserted anteriorly on the perineal body and pubic bone. The LAM had a common anterior attachment to the pubic bone, but separated posteriorly into puborectal and “pubovisceral” muscles. This pubovisceral muscle was bilayered: its internal layer attached to the conjoint longitudinal muscle of the rectum and the rectococcygeal fascia, while its outer, patchy layer reinforced the inner layer. ASC contraction makes the ano-rectal bend more acute and lifts the pelvic floor. Extensions of the rectal longitudinal smooth muscle to the coccygeal bone (rectococcygeal muscle), perineal body (rectoperineal muscle), and endopelvic fascia (conjoint longitudinal and pubovisceral muscles) formed a “diaphragm” at the inferior boundary of the mesorectum that suspended the anorectal junction. Its contraction should straighten the anorectal bend.

Conclusion

The serial-section approach settled contentious topographic issues of the pelvic floor. We propose that the ASC is involved in continence and the rectal diaphragm in defecation.     

Impact of metal pollution on fungal diversity and community structures

The impact of metal pollution on plant communities has been studied extensively in the past, but little is known about the effects of metal pollution on fungal communities that occur in metal‐polluted soils. Metal‐tolerant ecotypes of the ectomycorrhizal fungus Suillus luteus are frequently found in pioneer pine forests in the Campine region in Belgium on metal‐polluted soils. We hypothesized that metal pollution would play an important role in shaping below‐ground fungal communities that occur in these soils and that Suillus luteus would be a dominant player. To test these hypotheses, the fungal communities in a young pine plantation in soil polluted with zinc, and cadmium were studied using 454 amplicon pyrosequencing. Results show that zinc, cadmium and soil organic matter content were strongly correlated with the fungal community composition, but no effects on fungal diversity were observed. As hypothesized, S. luteus was found to be a dominant member of the studied fungal communities. However, other dominant fungal species, such as Sistotrema sp., Wilcoxina mikolae and Cadophora finlandica were found as well. Their presence in metal‐polluted sites is discussed.