Semiochemical strategies for sea louse control: host location cues

The development of behavioural bioassays and electrophysiological recording techniques has enabled the role of semiochemicals to be investigated for the first time in Lepeophtheirus salmonis (Kr?yer). Adult male sea lice L salmonis were activated by, and attracted to, salmon-conditioned water (SCW) and SCW extract. Non-host fish odours, turbot-conditioned water (TCW) and turbot-conditioned water extract (TCW extract), elicited activation but no attraction in the lice. Solid-phase extraction techniques were developed to extract low molecular weight components of fish odours, and biological activity was shown to be confined to these. Electrophysiological activity from aesthetascs in the first antennae was found and neural responses to odours were recorded from the antennal nerves. Preliminary experiments on individual chemicals (isophorone, 1-octen-3-ol) linked to salmon revealed behavioural activation and electrophysiological responses in adult male L salmonis. Isophorone was shown to be significantly attractive to sea lice when placed in a slow-release system in a perfused tank of seawater in a choice situation. Proof of concept has been established for successfully extracting odour cues from seawater, analysing their biological activity and applying these to slow-release technologies for field trapping of lice. Future work involving linked GC-MS techniques using behaviour, electrophysiological responses, and organolepsis will establish further host location cues specific to Atlantic salmon.     

Improved filter system for an equine artificial vagina

A polyester filter to separate the gel from the gel-free portion of the ejaculum is part of many equine artificial vaginas. The filter itself retains many spermatozoa. Therefore, filters fabricated from nylon, micromesh cloth with pore sizes of 30 or 37 m were evaluated together with a conventional polyester filter. Five ejaculates were collected from each of six stallions using each filter. Both nylon filters were effective in retaining gel. More spermatozoa were retained in the polyester filter than in the 30- or 37-m nylon filters (2.5, 0.5 and 0.6 × 10⁹ sperm; P less than 0.05). Because of the absorption of fluid and retention of spermatozoa by the polyester filter, with samples devoid of gel the polyester filter retained a number of spermatozoa about equal to the number recovered in the semen. Use of a nylon filter allowed recovery of more spermatozoa in the semen for ejaculates without gel and caused no greater loss of spermatozoa from samples with gel. We recommend that a 37 μm nylon filter be used rather than a polyester filter.     

Interaction of bluetongue virus with preimplantation embryos from mice and cattle

Preimplantation embryos from mice and cattle were exposed to bluetongue virus in vitro to determine whether the virus would replicate in these early embryos and, if so, what pathologic consequences would ensue. A high proportion of zona pellucida-free, 2-cell embryos and morulae from mice, and morulae from cattle became infected. The infection was rapidly cytopathic in embryos from both species. Indirect immunofluorescence was used to demonstrate accumulation of virus antigen in the blastomeres of these embryos. The zona pellucida of both murine and bovine embryos provided effective protection from virus present in culture fluid.     

江苏省实施兽药GSP试点工作的基本做法与推进思考

江苏省GSP试点工作通过加强组织领导、广泛宣传推动、强化培训指导和注重检查交流等措施,基本建立了兽药GSP制度的框架,进一步提高和统一了对兽药GSP的认识,提高了试点企业的质量管理水平。但在兽药GSP实施过程中,存在对其重要性认识不足,部分暂行管理办法内容与实际脱节,技术指导力量薄弱等问题。     

Non-target effects of the ‘push–pull’ habitat management strategy: Parasitoid activity and soil fauna abundance

We assessed the non-target effects of a habitat management system (‘push–pull’) on maize stemborer specialist natural enemy activity and soil Collembola. Two study sites in western Kenya were sampled. There were two treatments at each site, maize monocrop and ‘push–pull’. The latter comprised an intercrop of maize and Desmodium, Desmodium uncinatum Jacq., with Napier grass, Pennisetum purpureum (Schumach), as a trap crop planted around the edge of the plot (spaced 1 m from main crop). Trichogramma spp. were recovered from stemborer eggs while Cotesia sesamiae and Cotesia flavipes were recovered from stemborer larvae, and Dentichasmias busseolae from pupae. Mean number of eggs parasitized was significantly higher in the maize monocrop than in the ‘push–pull’ plots however proportions parasitized did not differ between the two systems. The number of larvae and pupae parasitized and dead from causes other than parasitism similarly did not differ between cropping systems. Proportions of larvae and pupae parasitized were significantly higher in the ‘push–pull’ than in the monocrop plots, indicating that the activity of larval and pupal parasitoids was enhanced. C. sesamiae female wasps were attracted to the volatiles from Desmodium flowers but not those from the leaves in a four-arm olfactometer bioassay. A total of 1530 individual Collembola in seven families were recovered from the plots. The ‘push-pull’ strategy did not have any significant effect on Collembola abundance and dominance. The factors underlying these observations and their implications are discussed.     

Patch dynamics and the design of nature reserves

Island biogeographic theory has been applied to the design of nature reserves. However, immigration, which is important in maintaining species equilibrium on true islands, will not contribute significantly to the maintenance of equilibrium on reserves in the future because of the disappearance of recolonisation sources. Consequently, extinction becomes the dominant population process, and the internal disturbance dynamics become the critical design feature of reserves. The design of reserves should be based on ‘minimum dynamic area’, the smallest area with a natural disturbance regime which maintains internal recolonisation sources and hence minimises extinctions. Determination of minimum dynamic area must be based on knowledge of disturbance-generated patch size, frequency, and longevity, and the mobilities of the preserved species. These features have not all been explicitly considered in the previous island biogeographic design recommendations.     

Novel genotypes of the subtropical grass Eragrostis curvula for the study of apomixis (diplospory)

The aim of this work was to obtain a series of genetically related lines of Eragrostis curvula with different ploidy levels and reproductive modes, which can be used for the discovery of genes associated to diplospory. E. curvula is a widely cultivated forage grass native to Southern Africa that reproduces naturally by obligate diplosporous apomixis (asexual reproduction by seeds) of the Antennaria type. In vitro culture of immature inflorescences of the apomictic cultivar Tanganyika led to the regeneration of a diploid plant with a particular morphology (plant UNST1122). Embryo sac analysis and progeny tests determined that plant UNST1122 reproduces by sexuality. UNST1122 was cloned by dividing its tillers and a R ₁ generation was obtained from seeds after open pollination among the diploid clones. A set of 500 seeds from a diploid R ₁ plant was treated with colchicine and two plants showing a duplicated chromosome number (2n = 4x = 40) were obtained (plants UNST1112 and UNST1131). Progeny tests using RAPDs indicated that these plants reproduce also by sexuality. The availability of sexual tetraploid genotypes of E. curvula will allow the production of hybrids with new interesting combinations of agronomic traits and the developing of mapping populations segregating for diplospory. Besides, these genetically related plants with different reproduction modes constitutes an excellent model for the identification of gen(es) involved in diplosporous apomixis by mRNA profiling as well as to study the genomic rearrangements and gene expression alterations associated to changes at ploidy levels.     

Recharge in Volcanic Systems: Evidence from Isotope Profiles of Phenocrysts

Strontium isotope ratios measured from core to rim across plagioclase feldspar crystals can be used to monitor changes in the isotope composition of the magma from which they grew. In samples from three magma systems from convergent margin volcanoes, sudden changes in major element composition, petrographic features, and strontium isotope composition were found to correspond to discrete magmatic events, most likely repeated recharge of more mafic magma with lower ratios of strontium-87 to strontium-86 into a crustally contaminated magma.     

90 years of forest cover change in an urbanizing watershed: spatial and temporal dynamics

Landscape structure in the Eastern US experienced great changes in the last century with the expansion of forest cover into abandoned agricultural land and the clearing of secondary forest cover for urban development. In this paper, the spatial and temporal patterns of forest cover from 1914 to 2004 in the Gwynns Falls watershed in Baltimore, Maryland were quantified from historic maps and aerial photographs. Using a database of forest patches from six times—1914, 1938, 1957, 1971, 1999, and 2004—we found that forest cover changed, both temporally and spatially. While total forest area remained essentially constant, turnover in forest cover was very substantial. Less than 20% of initial forest cover remained unchanged. Forest cover became increasingly fragmented as the number, size, shape, and spatial distribution of forest patches within the watershed changed greatly. Forest patch change was also analyzed within 3-km distance bands extending from the urban core to the more suburban end of the watershed. This analysis showed that, over time, the location of high rates of forest cover change shifted from urban to suburban bands which coincides with the spatial shift of urbanization. Forest cover tended to be more stable in and near the urban center, whereas forest cover changed more in areas where urbanization was still in process. These results may have critical implications for the ecological functioning of forest patches and underscore the need to integrate multi-temporal data layers to investigate the spatial pattern of forest cover and the temporal variations of that spatial pattern.