Host selection,oviposition behaviour and leaf traits in a specialist willow sawfly on species of Salix (Salicaceae)

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Oviposition,larval survival and leaf damage by the willow leaf blotch miner,Micrurapteryx salicifoliella,in relation to leaf trichomes across 10 Salix species

1. Foliar trichomes clearly reduce chewing damage and efficiency of movement by some insect herbivores, but the effect of trichomes on insect oviposition is less well characterised. Trichomes are likely to have particularly strong, negative effects on species that require secure attachment of the egg to the leaf epidermis for successful transition to the feeding stage – a group that includes many leaf mining insects. 2. One such species, Micrurapteryx salicifoliella, must initially enter leaf cells directly from an egg adhered to the cuticle, but later instars can move between leaves and initiate new mines from the leaf exterior. 3. Natural patterns of occurrence by M. salicifoliella were quantified on 10 sympatric Salix species varying in trichome expression to test whether trichomes were associated with reduced oviposition, larval survival and leaf damage. 4. Mean egg density and leaf mining damage were negatively related to mean trichome density across Salix species. Survival of M. salicifoliella from egg to pupa was positively related to trichome density, suggesting that initiation of new mines by late‐instar larvae was not adversely affected by trichomes. There was no evidence that trichomes benefited leaf miner larvae indirectly by decreasing density‐dependent mortality; rather, the positive relationship between trichome density and larval survival may reflect less effective chemical defence by Salix species expressing high trichome density. 5. The results suggest that foliar trichomes serve as an effective defence against M. salicifoliella by deterring oviposition, but do not reduce the survivorship of those individuals that successfully transition from egg to larva.     

Development of the Recalcitrant (Homoiohydrous) Seeds of Avicennia marina: Anatomical, Ultrastructural and Biochemical Events Associated with Development from Histodifferentiation to Maturation

Early histodifferentiation of the embryo of Avicennia marina(Forssk) Vierh was characterized by the formation of endospermhaustoria Once the growth phase was initiated, subsequent embryodevelopment was extra-ovular The mature seed, therefore, wasenclosed by a pericarp originating entirely from the ovary wallGrowth and reserve deposition was not initiated until 45–50d after fruit set (DAFS), when respiratory activity had peakedWater content remained constant from the earliest stages ofembryogenesis to seed abscission and respiratory activity, althoughdeclining somewhat after the completion of histodifferentiation,remained relatively high throughout seed development The ultrastructureof the meristematic root primordia was indicative of metabolicactivity, remaining essentially similar in all respects fromthe end of histodifferentiation until the mature seeds wereabscised During this phase cotyledon cells became highly vacuolatedand the soluble sugars, which constituted the major nutrientreserves of mature seeds, increased considerably Seeds of A,marina initiate germination, without the requirement for additionalwater, as soon as they are shed It is proposed that the accumulationof soluble sugars, rather than insoluble complex reserves, isa major factor in the developmental strategy of these highlyrecalcitrant seeds Anatomy, Avicennia marina, biochemistry, homoiohydrous, recalcitrant, seed development/maturation, ultrastructure     

Population biology of swift (Apus apus) ectoparasites in relation to host reproductive success

Abstract.

• 1 We censused ectoparasite populations of adult and nestling swifts over the course of the host's breeding season. Nearly all of the birds were infested with chewing lice and two-thirds of the nests were infested with louse flies. Feather mites were observed but not quantified.
• 2 Lice and louse flies both showed aggregated distributions among hosts. Louse eggs, hatched lice and adult louse flies had negative binomial distributions, whereas the aggregated distribution of louse fly pupae was not adequately described by negative binomial or Poisson models.
• 3 Transmission of lice from parents to offspring was documented. A comparison of the age structure of lice on parents and offspring indicated that most transmission was by nymphal lice.
• 4 Host reproductive success and survival appeared to be independent of the number of lice or louse flies. Neither parasite correlated with the number, body mass, or date of fledging of young birds, nor with the overwinter survival of adults. We caution, however, that experimental manipulations of parasite load are required for a definitive test of the impact of ectoparasites on evolutionary fitness components.

     

Gram-Chromotrope: a New Technique that Enhances Detection of Microsporidial Spores in Clinical Samples

We have developed a new staining procedure that combines the traditional Gram staining for bacteria and the Weber's chromotrope staining method, the standard technique for the detection of microsporidia spores in clinical Specimens. This “Gram-chromotrope” staining technique enhances the staining characteristics of microsporidia spores and facilitates the easy detection and differentiation of spores from other microorganisms that are found in clinical specimens, especially stool samples. This new technique is fast, reliable, and simple to perform, and can be easily adapted for use in clinical laboratories.     

RNA silencing-mediated resistance to a crinivirus (Closteroviridae) in cultivated sweetpotato (Ipomoea batatas L.) and development of sweetpotato virus disease following co-infection with a potyvirus

Sweetpotato chlorotic stunt virus (SPCSV; genus Crinivirus , family Closteroviridae) is one of the most important pathogens of sweetpotato ( Ipomoea batatas L.). It can reduce yields by 50% by itself and cause various synergistic disease complexes when co-infecting with other viruses, including sweetpotato feathery mottle virus (SPFMV; genus Potyvirus , family Potyviridae). Because no sources of true resistance to SPCSV are available in sweetpotato germplasm, a pathogen-derived transgenic resistance strategy was tested as an alternative solution in this study. A Peruvian sweetpotato landrace 'Huachano' was transformed with an intron-spliced hairpin construct targeting the replicase encoding sequences of SPCSV and SPFMV using an improved genetic transformation procedure with reproducible efficiency. Twenty-eight independent transgenic events were obtained in three transformation experiments using a highly virulent Agrobacterium tumefaciens strain and regeneration through embryogenesis. Molecular analysis indicated that all regenerants were transgenic, with 1–7 transgene loci. Accumulation of transgene-specific siRNA was detected in most of them. None of the transgenic events was immune to SPCSV, but ten of the 20 tested transgenic events exhibited mild or no symptoms following infection, and accumulation of SPCSV was significantly reduced. There are few previous reports of RNA silencing-mediated transgenic resistance to viruses of Closteroviridae in cultivated plants. However, the high levels of resistance to accumulation of SPCSV could not prevent development of synergistic sweet potato virus disease in those transgenic plants also infected with SPFMV.     

Trypanosoma cruzi: Quantification and Analysis of the Infectivity of Cloned Stocks1

The infection of bovine embryo skin and muscle cells by trypomastigotes of four Trypanosoma cruzi clones (CA-I/71, /72, Miranda/76, /80) was quantified. Stable and reproducible intra-isolate differences were observed; an almost 70-fold difference in infectivity occurred between clones. The CA-I/71 clone was not susceptible to N-acetyl-D-glucosamine at a concentration that inhibits the infection of vertebrate cells by Ernestina and Y-strain parasites. Eight other monosaccharides that are common constitutents of vertebrate cell surface glycoproteins also failed to inhibit the infection of vertebrate cells by the CA-I/71 clone.     

Metal resistances of Chlorophyta from rivers polluted by heavy metals

SUMMARY. Two-hundred isolates, comprising 87 species of Chlorophyta, were obtained from sites along the Rivers Hayle and Gannel. which drain the ancient mining region of Cornwall. All isolates were tested for sensitivity to copper, lead, zinc and cadmium. In general, isolates were resistant to the metals normally present in their habitats. However, the distribution of metal sensitivities of the algae from a given site was broad; the effect of metal pollution was to shift the median response of a population toward higher metal resistance. Resistant algae of two general classes were identified: some normally sensitive species were metal-tolerant, presumably through genetic adaptation; other species were metal-resistant even when isolated from a non-polluted habitat. Many isolates of both types displayed multiple-resistances or co-tolerances. For example, copper tolerant isolates from high copper sites tended to be also lead resistant; however, algae from high lead sites were usually very copper sensitive. Zinc and cadmium resistances also were correlated among isolates from both zinc-polluted and non-polluted sites. General metal-insensitivity seemed to be common, particularly among gelatinous Chlamydomonas and Gloeococcus species. Thus, several evolutionary strategies appear to coexist among algae from metal polluted environments.