Effect of temperature on survival, development and reproduction of the predatory lacewing Dichochrysa prasina (Neuroptera: Chrysopidae) reared on Ephestia kuehniella eggs (Lepidoptera: Pyralidae)

Preimaginal development and adult longevity and reproduction of Dichochrysa prasina Burmeister were studied at six constant temperatures (15, 20, 25, 27, 30 and 33 °C) and a photoperiod of 16:8 (L:D). Eggs of the flour moth Ephestia kuehniella (Zeller) were used as food throughout preimaginal development, whereas the adults of D. prasina fed on a liquid diet of water, yeast hydrolysate, sugar and honey. At the highest tested temperature of 33 °C no larvae completed their development. At the rest of the tested temperatures the egg to adult developmental period ranged from approximately 92 days at 15 °C to 25 days at 30 °C. Percentages of adult emergence ranged from 36% at 15 °C to 84% at 30 °C. Both adult longevity and fecundity were significantly affected by temperature and the intrinsic rate of increase (r_m) reached its maximum value at 27 °C. These results could be useful for the establishment of a small scale rearing and mass production of D. prasina.     

Effect of relative humidity on development, survival and reproduction of the predatory lacewing Dichochrysa prasina (Neuroptera: Chrysopidae)

The effect of five constant relative humidity (RH) regimes (12%, 33%, 55%, 75% and 94%) on the preimaginal development and adult longevity and reproduction of Dichochrysa prasina Burmeister was studied at 26 ± 1 °C and a photoperiod of 16:8 (L:D) under laboratory conditions. For the experiments, larvae were fed individually on eggs of the flour moth Ephestia kuehniella (Zeller), whereas adults on a liquid diet consisting of water, yeast hydrolysate, sugar and honey. The experimental insects were maintained individually in sealed plastic containers with saturated water salt solutions at the base to control RH. Preimaginal developmental time from egg to adult for females and males was significantly shorter at 75% and 94% RHs than at other RHs in the range from 12% to 55%. Percentages of adult emergence were similar at all RHs tested and varied from 52.5% to 75.0%. Adult females that had no access to water and were maintained at 12%–75% RH lived on average less than two weeks and laid no eggs, whereas at 94% RH they lived longer and each laid on average 201 eggs. When the females had periodic access to a water source a significant increase in both longevity and egg production occurred and the estimated intrinsic rate of increase was high, irrespective of RH. These results could be useful for the mass-rearing of D. prasina and for better understanding its population dynamics under field conditions.     

Protein profiling of the dimorphic, pathogenic fungus, Penicillium marneffei

Background

Penicillium marneffei is a pathogenic fungus that afflicts immunocompromised individuals having lived or traveled in Southeast Asia. This species is unique in that it is the only dimorphic member of the genus. Dimorphism results from a process, termed phase transition, which is regulated by temperature of incubation. At room temperature, the fungus grows filamentously (mould phase), but at body temperature (37°C), a uninucleate yeast form develops that reproduces by fission. Formation of the yeast phase appears to be a requisite for pathogenicity. To date, no genes have been identified in P. marneffei that strictly induce mould-to-yeast phase conversion. In an effort to help identify potential gene products associated with morphogenesis, protein profiles were generated from the yeast and mould phases of P. marneffei.

Results

Whole cell proteins from the early stages of mould and yeast development in P. marneffei were resolved by two-dimensional gel electrophoresis. Selected proteins were recovered and sequenced by capillary-liquid chromatography-nanospray tandem mass spectrometry. Putative identifications were derived by searching available databases for homologous fungal sequences. Proteins found common to both mould and yeast phases included the signal transduction proteins cyclophilin and a RACK1-like ortholog, as well as those related to general metabolism, energy production, and protection from oxygen radicals. Many of the mould-specific proteins identified possessed similar functions. By comparison, proteins exhibiting increased expression during development of the parasitic yeast phase comprised those involved in heat-shock responses, general metabolism, and cell-wall biosynthesis, as well as a small GTPase that regulates nuclear membrane transport and mitotic processes in fungi. The cognate gene encoding the latter protein, designated RanA, was subsequently cloned and characterized. The P. marneffei RanA protein sequence, which contained the signature motif of Ran-GTPases, exhibited 90% homology to homologous Aspergillus proteins.

Conclusion

This study clearly demonstrates the utility of proteomic approaches to studying dimorphism in P. marneffei. Moreover, this strategy complements and extends current genetic methodologies directed towards understanding the molecular mechanisms of phase transition. Finally, the documented increased levels of RanA expression suggest that cellular development in this fungus involves additional signaling mechanisms than have been previously described in P. marneffei.     

Receptor Specificity and Transmission of H2N2 Subtype Viruses Isolated from the Pandemic of 1957

Influenza viruses of the H2N2 subtype have not circulated among humans in over 40 years. The occasional isolation of avian H2 strains from swine and avian species coupled with waning population immunity to H2 hemagglutinin (HA) warrants investigation of this subtype due to its pandemic potential. In this study we examined the transmissibility of representative human H2N2 viruses, A/Albany/6/58 (Alb/58) and A/El Salvador/2/57 (ElSalv/57), isolated during the 1957/58 pandemic, in the ferret model. The receptor binding properties of these H2N2 viruses was analyzed using dose-dependent direct glycan array-binding assays. Alb/58 virus, which contains the 226L/228S amino acid combination in the HA and displayed dual binding to both alpha 2,6 and alpha 2,3 glycan receptors, transmitted efficiently to naïve ferrets by respiratory droplets. Inefficient transmission was observed with ElSalv/57 virus, which contains the 226Q/228G amino acid combination and preferentially binds alpha 2,3 over alpha 2,6 glycan receptors. However, a unique transmission event with the ElSalv/57 virus occurred which produced a 226L/228G H2N2 natural variant virus that displayed an increase in binding specificity to alpha 2,6 glycan receptors and enhanced respiratory droplet transmissibility. Our studies provide a correlation between binding affinity to glycan receptors with terminal alpha 2,6-linked sialic acid and the efficiency of respiratory droplet transmission for pandemic H2N2 influenza viruses.