Population structure of Argas arboreus (Acari: Argasidae) ticks associated with seasonally abandoned mixed heronries, dominated by cattle egrets (Bubulcus ibis), in South Africa

During winter populations of Argas arboreus from heronries of the cattle egret, Bubulcus ibis, in South Africa are composed of adults, with some predominance of males, and II-IV instar nymphs, in a state of diapause. The period of tick activity, including reproduction and development of eggs, larvae and N1 nymphs, is synchronized with the nesting and breeding season of their avian hosts. It begins during spring with the return of birds to the heronry, and ceases in autumn through induction of reproductive diapause in engorged females, and behavioural diapause in unfed nymphs and adult ticks. Many ticks showed morphological anomalies and malformations, the study of which could possibly be used for monitoring of environmental pollution.     

Nymphal diapause and its photoperiodic control in the tick Ixodes scapularis (Acari: Ixodidae)

It is shown experimentally that the option between developmental diapause and non-diapause development in nymphs of Ixodes scapularis Say, 1821 (Middle Atlantic population) is determined by photoperiodic conditions according to a two-step photoperiodic reaction of short-day long-day type. Diapause arrest of development is induced by an impact of either long day upon unfed nymphs, or short day upon engorged nymphs, while non-diapause development completed in 2-2.5 months at 20 degrees C needs the change from short-day to long-day conditions. Some ecophysiological aspects of mechanisms controlling seasonal development of ticks belonging to Ixodes ricinus complex are discussed.     

Chemical structure of terrestrial humus materials formed from different vegetation characterized by solid-state 13C NMR with CP-MAS techniques

Eleven samples of terrestrial humus from different vegetational backgrounds were examined with solid-state ¹³C NMR using cross-polarization and magic-angle spinning (CP-MAS). In addition, all the samples were run with a dipolar dephasing pulse sequence for non-quarternary carbon suppression (NQS). The humus samples all appeared to contain small amounts of aromatic substances and larger amounts of aliphatic compounds. Most of the samples contained considerable amounts of hydroxyl groups and acetals, which originate mainly from carbohydrates. No correlations were found between vegetational background and chemical structure.     

Particle nucleation in the tropical boundary layer and its coupling to marine sulfur sources

New particle formation in a tropical marine boundary layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being linked to the natural marine sulfur cycle. This conclusion was based on real-time observations of dimethylsulfide, sulfur dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, aerosol size and number distribution, and total aerosol surface area. Classic binary nucleation theory predicts no nucleation under the observed marine boundary layer conditions.     

Changes in the Metagenome of Prokaryotic Community as an Indicator of Fertility of Arable Soddy-Podzolic Soils upon Fertilizer Application

The influence of different systems of fertilization and liming on the changes in the taxonomic structure of prokaryotic community in arable soddy-podzolic soil (Albic Retisol (Loamic, Aric, Cutanic, Differentic, Ochric)) was studied in a stationary field experiment of Vologda State Dairy Farming Academy with the use of high-performance sequencing method of gene 16S rRNA. The 25-year-old fallow plot, in which the intensity of microbiological processes was close to that in the virgin soddy-podzolic soils, was used as a control. At the first stage, dominant phyla were identified: Proteobacteria (45.3–56.2%), Actinobacteria (13.6–20.4%), Bacteroidetes (7.2–19.3%), Acidobacteria (7.1–11.5%), and Verrucomicrobia (4.3–10.3%). Several groups of microorganisms-indicators, whose portion changes in the arable soil under the influence of liming, fertilizer application, and soil treatment in comparison with the control, were determined. The applied approach made it possible to relate the taxonomic structure of the soil microbial cenosis with external factors for assessing changes in the structure of soil microbial complex under the impact of different uses of the arable soil.     

Ethics and Genetic Selection in Purebred Dogs

There is an ongoing revolution in medicine that is changing the way that veterinarians will be counselling clients regarding inherited disorders. Clinical applications will emerge rapidly in veterinary medicine as we obtain new information from canine and comparative genome projects ( Meyers‐Wallen 2001 : Relevance of the canine genome project to veterinary medical practice. International Veterinary Information Service, New York). The canine genome project is described by three events: mapping markers on canine chromosomes, mapping gene locations on canine chromosomes ( Breen et al. 2001 : Genome Res. 11, 1784–1795), and obtaining the nucleotide sequence of the entire canine genome. Information from such research has provided a few DNA tests for single gene mutations [ Aguirre 2000 : DNA testing for inherited canine diseases. In: Bonagura, J (ed), Current Veterinary Therapy XIII. Philadelphia WB Saunders Co, 909–913]. Eventually it will lead to testing of thousands of genes at a time and production of DNA profiles on individual animals. The DNA profile of each dog could be screened for all known genetic disease and will be useful in counselling breeders. As part of the pre‐breeding examination, DNA profiles of prospective parents could be compared, and the probability of offspring being affected with genetic disorders or inheriting desirable traits could be calculated. Once we can examine thousands of genes of individuals easily, we have powerful tools to reduce the frequency of, or eliminate, deleterious genes from a population. When we understand polygenic inheritance, we can potentially eliminate whole groups of deleterious genes from populations. The effect of such selection on a widespread basis within a breed could rapidly improve health within a few generations. However, until we have enough information on gene interaction, we will not know whether some of these genes have other functions that we wish to retain. And, other population effects should not be ignored. At least initially it may be best to use this new genetic information to avoid mating combinations that we know will produce affected animals, rather than to eliminate whole groups of genes from a population. This is particularly important for breeds with small gene pools, where it is difficult to maintain genetic diversity. Finally, we will eventually have enough information about canine gene function to select for specific genes encoding desirable traits and increase their frequencies in a population. This is similar to breeding practices that have been applied to animals for hundreds of years. The difference is that we will have a large pool of objective data that we can use rapidly on many individuals at a time. This has great potential to improve the health of the dog population as a whole. However, if we or our breeder clients make an error, we can inadvertently cause harm through massive, rapid selection. Therefore, we should probably not be advising clients on polygenic traits or recommend large scale changes in gene frequencies in populations until much more knowledge of gene interaction is obtained. By then it is likely that computer modelling will be available to predict the effect of changing one or several gene frequencies in a dog population over time. And as new mutations are likely to arise in the future, these tools will be needed indefinitely to detect, treat and eliminate genetic disorders from dog populations. Information available from genetic research will only be useful in improving canine health if veterinarians have the knowledge and skills to use it ethically and responsibly. There is not only a great potential to improve overall canine health through genetic selection, but also the potential to do harm if we fail to maintain genetic diversity. Our profession must be in a position to correctly advise clients on the application of this information to individual dogs as well as to populations of dogs, and particularly purebred dogs.