Honeybees and nectar nicotine: deterrence and reduced survival versus potential health benefits

Secondary metabolites produced by plants for herbivore defence are often found in floral nectar, but their effect on the foraging behaviour and physiological performance of pollinators is largely unknown. Nicotine is highly toxic to most herbivores, and nicotine-based insecticides may contribute to current pollinator declines. We examined the effects of nectar nicotine on honeybee foraging choices and worker longevity. Free-flying honeybee (Apis mellifera scutellata) workers from six colonies were given a choice between multiple nicotine concentrations (0-1000 μM) in artificial nectar (0.15-0.63 M sucrose). The dose-dependent deterrent effect of nicotine was stronger in lower sugar concentrations, but even the highest nicotine concentrations did not completely repel honeybees, i.e., bees did not stop feeding on these diets. Nicotine in nectar acts as a partial repellent, which may keep pollinators moving between plants and enhance cross-pollination. In the second part of the study, newly emerged workers from 12 colonies were caged and fed one of four nicotine concentrations (0-300 μM) in 0.63 M sucrose for 21 days. Moderate (≤30 μM) nicotine concentrations had no significant detrimental effect, but high nicotine concentrations reduced the survival of caged workers and their nectar storage in the honey comb. In contrast, worker groups that survived poorly on sugar-only diets demonstrated increased survival on all nicotine diets. In the absence of alternative nectar sources, honeybees tolerate naturally occurring nectar nicotine concentrations; and low concentrations can even be beneficial to honeybees. However, high nicotine concentrations may have a detrimental effect on colony fitness.

LEVANTAMENTO DAS FAMÍLIAS DE HIMENÓPTEROS PARASITOIDES ASSOCIADOS AO CULTIVO DE TABACO (NICOTIANA TABACUM L.) EM SANTA CRUZ DO SUL E LAGOÃO,RIO GRANDE DO SUL, BRASIL

RESUMO O objetivo deste trabalho foi realizar o levantamento das famílias de himenópteros parasitoides associados ao cultivo do tabaco (Nicotiana tabacum L) no Estado do Rio Grande do Sul. Foram realizadas coletas quinzenais com armadilhas de Malaise, pitfalls e bandejas amarelas em lavouras de tabaco nos municípios de Santa Cruz do Sul e Lagoão. Durante o período de novembro de 2007 a fevereiro de 2008, foram coletados 1.047 indivíduos da ordem Hymenoptera. Destes, 738 parasitoides estão distribuídos em 23 famílias. Ichneumonidae, Braconidae e Scelionidae foram as famílias mais abundantes, representando 44,6%, 14,9% e 11,5% dos indivíduos parasitoides coletados, respectivamente.

First report of Elasmus polistis Burks (Hymenoptera: Eulophidae) recovered from Polistes versicolor (Olivier) (Hymenoptera: Vespidae) nests in Brazil

The first record of Elasmus polistis Burks in Polistes versicolor (Olivier) nests in the Rio Grande do Sul state and in Brazil is provided. A total of 173 specimens of P. versicolor and 790 specimens of E. polistis were collected from two nests from Gramado and Santa Cruz do Sul, RS, Brazil.

Sex-specific biochemical and histological differences in gonads of sea urchins (Psammechinus miliaris) and their response to phenanthrene exposure

Female and male individuals of the same species often differ with respect to their susceptibility to toxicant stress. In the present study, sea urchins (Psammechinus miliaris) of both sexes were exposed to high (150 μg L⁻¹) and environmentally relevant (5 μg L⁻¹) concentrations of phenanthrene over 10 days. While food intake was significantly decreased following exposure to 150 μg L⁻¹ phenanthrene, histological indices (lipofuscin accumulation, fibrosis, oocyte atresia), energetic status (energy charge, sum adenylates, AMP/ATP ratio) as well as ascorbate levels in the gonads showed either little or no effect upon phenanthrene exposure. However, most parameters (vitamin C, energy charge, sum adenylates, AMP/ATP ratio, ATP and ADP concentrations, lipofuscin content, fibrosis) significantly differed between male and female animals. This study illustrates the difficulties to identify toxic injury in reproductive tissue as it may be superimposed by gametogenesis and spawning of gametes.

Dilute bird nectars: viscosity constrains food intake by licking in a sunbird

Floral nectars of bird-pollinated plants are relatively dilute. One hypothesis proposed to explain this concerns the difficulty for birds of drinking nectar of high viscosity. We examined the effects of viscosity, separately from those of sugar concentration, on feeding by captive whitebellied sunbirds (Cinnyris talatala). Viscosities of artificial nectar (sucrose solutions ranging in concentration from 0.25 to 1.5 mol/l) were altered with Tylose, an inert polysaccharide. Food consumption was measured over 3 h, and lick frequency and duration were recorded using photodetection devices on feeding apertures too small for the bill but large enough for the extended tongue. Volumetric intake rates (ml/s) were inversely proportional to nectar viscosity, and were similar over the range of sucrose concentrations when viscosity was held constant. Sucrose intake rates (mg/s) remained the same on pure sucrose solutions, but they decreased with increasing viscosity at a constant sucrose concentration. Lick frequencies and tongue loads were reduced at high viscosities, and lick duration increased, which confirms that sunbirds take longer to ingest viscous solutions. Licking behavior was remarkably similar in birds feeding on different sucrose concentrations if viscosity was held constant. Nectar ingestion rate is determined by viscosity; however, total food intake is mainly modulated by sugar concentration. Similar effects of food viscosity have been observed in insects that suck nectar.

Gonadal lesions of female sea urchin (Psammechinus miliaris) after exposure to the polycyclic aromatic hydrocarbon phenanthrene

Histopathological alterations in the reproductive tissue of the female sea urchin Psammechinus miliaris after exposure to the polycyclic aromatic hydrocarbon (PAH) phenanthrene were investigated using light microscopy. Sexually mature sea urchins were exposed to 500 microg L(-1) phenanthrene for 20 days. A severe disorganisation of the acinal structure of the gonads was observed in phenanthrene-treated animals, mainly as a result of aggregates of degenerating previtellogenic oocytes. Growth and maturation of previtellogenic oocytes were inhibited, whereas there were no obvious effects on vitellogenic oocytes and mature ova. The acinal wall showed signs of fibrosis as well as dilation of the two epithelial layers. Phenanthrene severely affected the reproductive function of the sea urchins since a proper oogenesis of the ovarian tissue is very unlikely. Generally, the observed alterations are similar to histopathological changes in reproductive tissue in other invertebrates after exposure to PAHs and oil.

High viral load of human wart-associated papillomaviruses (PV) but not beta-PV in cutaneous warts independent of immunosuppression

BACKGROUND

A broad spectrum of human papillomaviruses (HPV) has been detected in warts from immunocompetent patients and a much more diverse range from immunosuppressed organ transplant recipients (OTR).

OBJECTIVES

To determine the HPV types in warts from OTR, we assessed present infections of mucosal (alpha-PV), wart-associated (alpha-, micro- and nu-PV) and cutaneous HPV types (beta-/gamma-PV) in immunocompetent patients and OTR. Patients/methods Forty-one warts from 29 immunocompetent patients (non-OTR) and 53 warts from 33 OTR were analysed for DNA of human alpha-, beta-, gamma-, micro- and nu-PV. For frequent types viral load was determined by quantitative real-time PCR.

RESULTS

Compared with non-OTR prevalence of cutaneous HPV (79% vs. 49%, P < 0.01) and the number of multiple infections (62% vs. 17%, P < 0.0001) were significantly increased. The mean viral load of the wart-associated HPV was more than 10(5)-fold higher compared with human beta-PV in both cohorts.

CONCLUSIONS

The high load of wart-associated HPV suggests an active role of these viruses rather than cutaneous types in warts independent of immunosuppression; however, the substantial fraction of warts with low HPV genome copies remains to be explained.

Optical study of LaO0.9F0.1FeAs: evidence for a weakly coupled superconducting state

We have studied the reflectance of the recently discovered superconductor LaO0.9F0.1FeAs in a wide energy range from the far infrared to the visible regime. We report on the observation of infrared active phonons, the plasma edge, and possible interband transitions. On the basis of this data and the reported in-plane penetration depth lambda{L}(0)=254 nm [H. Luetkens, Phys. Rev. Lett. 101, 097009 (2008)] a disorder sensitive relatively small value of the total electron-boson coupling constant lambda{tot}=lambda{e-ph}+lambda{e-sp} approximately 0.6+/-0.35 can be estimated adopting an effective single-band picture.

High-field pauli-limiting behavior and strongly enhanced upper critical magnetic fields near the transition temperature of an arsenic-deficient LaO0.9F0.1FeAs1-delta superconductor

We report upper critical field Bc2(T) data for disordered (arsenic-deficient) LaO0.9F0.1FeAs1-delta in a wide temperature and magnetic field range up to 47 T. Because of the large linear slope of Bc2 approximately -5.4 to -6.6 T/K near Tc approximately 28.5 K, the T dependence of the in-plane Bc2(T) shows a flattening near 23 K above 30 T which points to Pauli-limited behavior with Bc2(0) approximately 63-68 T. Our results are discussed in terms of disorder effects within [corrected] unconventional superconducting pairings.