Ecological risk assessment of endocrine disruptors.
(65/1525)
The European Centre for Ecotoxicology and Toxicology of Chemicals proposes a tiered approach for the ecological risk assessment of endocrine disruptors, integrating exposure and hazard (effects) characterization. Exposure assessment for endocrine disruptors should direct specific tests for wildlife species, placing hazard data into a risk assessment context. Supplementing the suite of mammalian screens now under Organization for Economic Cooperation and Development (OECD) validation, high priority should be given to developing a fish screening assay for detecting endocrine activity in oviparous species. Taking into account both exposure characterization and alerts from endocrine screening, higher tier tests are also a priority for defining adverse effects. We propose that in vivo mammalian and fish assays provide a comprehensive screening battery for diverse hormonal functions (including androgen, estrogen, and thyroid hormone), whereas Amphibia should be considered at higher tiers if there are exposure concerns. Higher tier endocrine-disruptor testing should include fish development and fish reproduction tests, whereas a full life-cycle test could be subsequently used to refine aquatic risk assessments when necessary. For avian risk assessment, the new OECD Japanese quail reproduction test guideline provides a valuable basis for developing a test to detecting endocrine-mediated reproductive effects; this species could be used, where necessary, for an avian life-cycle test. For aquatic and terrestrial invertebrates, data from existing developmental and reproductive tests remain of high value for ecological risk assessment. High priority should be given to research into comparative endocrine physiology of invertebrates to support data extrapolation to this diverse fauna. (+info)
Genome resource banking for wildlife research, management, and conservation.
(66/1525)
Cryobiology offers an important opportunity to assist in the management and study of wildlife, including endangered species. The benefits of developing genome resource banks for wildlife are profound, perhaps more so than for traditional uses in terms of livestock and human fertility. In addition to preserving heterozygosity and assisting in the genetic management of rare populations held in captivity, frozen repositories help insure wild populations against natural and human-induced catastrophes. Such banks also are an invaluable source of new knowledge (for basic and applied research) from thousands of species that have yet to be studied. However, it is crucial that genome resource banks for wildlife species be developed in a coordinated fashion that first benefits the conservation of biodiversity. Spurious collections will be of no advantage to genuine conservation. The Conservation Breeding Specialist Group (CBSG; of the International Union for the Conservation of Nature and Natural Resources' Species Survival Commission) has promoted international dialogue on this topic. CBSG working groups have recognized that such repositories be developed according to specific, scientific guidelines consistent with an international standard that ensures practicality, high-quality ethics, and cost-effectiveness. Areas requiring priority attention also are reviewed, including the need for more basic research, advocacy, and support for developing organized repositories of biomaterials representing the world's diverse biota. (+info)
Pericentromeric organization at the fusion point of mouse Robertsonian translocation chromosomes.
(67/1525)
In mammals, Robertsonian (Rb) translocation (the joining of two telo/acrocentric chromosomes at their centromere to form a metacentric) is the most effective process in chromosomal evolution leading to speciation; its occurrence also affects human health (through the induction of trisomies) and the fertility of farm animals. To understand the mechanism of Rb translocation, we used the house mouse as a model system and studied the organization of pericentromeric satellite DNAs (satDNA) of telocentrics and Rb chromosomes, both minor and major satDNA. The chromosome-orientation fluorescence in situ hybridization (CO-FISH) technique was used to analyze the major satDNA. To detect the very small amount of minor satDNA, a procedure was developed that combines CO-FISH with primed in situ labeling and conventional FISH and is five times more sensitive than the CO-FISH procedure alone. It was found that both the major and the minor satDNA tandem repeats are oriented head-to-tail in telocentric and Rb chromosomes, and their polarity is always the same relative to the centromere. We suggest that all tandemly repetitive satDNAs in a species probably are locked into such a symmetry constraint as a universal consequence of chromosomal evolution. Rb translocation breakpoints were found localized within the minor satDNA of telocentrics, and these sequences contributed symmetrically to the formation of the centromeric region of the Rb chromosomes. These results are important for an understanding of the geometry of Rb translocations and suggest the study of DNA orientation as a new tool for investigating these rearrangements. (+info)
Prevalence of IgG antibodies response to Borrelia burgdorferi s.l. in populations of wild rodents from Mazury lakes district region of Poland.
(68/1525)
Three rodent species: Clethrionomys glareolus, Apodemus flavicollis and Microtus arvalis from Mazury Lakes District of Poland were examined for antibodies to Borrelia burgdorferi by enzyme-labelled protein G assay (ELGA). C. glareolus had an exceptionally high prevalence of B. burgdorferi antibodies - 58%, but A. flavicollis and M. arvalis also showed significant prevalence of 16.6% and 10.5%, respectively. The ELGA method is highly specific with good reproducibility. Nevertheless, some differences of sensitivity of assessed samples were season dependent. However, high seroprevalence did not coincide with infestation rates of examined rodents by I. ricinus ticks. The results indicated that in Mazury Lakes District, naturally infected rodents play an important role as an animal reservoir host for B. burgdorferi, and these animals may increase the risk of human infections in some habitats used as recreation areas. Also, this study shows that ELGA method based on the affinity of protein G for IgG of wild animals may be widely used to determine the competent zoonotic reservoir of B. burgdorferi. (+info)
Genetic variability and prevalence of Bartonella henselae in cats in Berlin, Germany, and analysis of its genetic relatedness to a strain from Berlin that is pathogenic for humans.
(69/1525)
Nineteen Bartonella henselae strains and one Bartonella clarridgeiae strain were isolated from blood samples of 97 pet cats and 96 stray cats from Berlin, Germany, indicating prevalence rates of 1 and 18.7%, respectively, for B. henselae and 0 and 1%, respectively, for B. clarridgeiae. Eighteen of 19 B. henselae isolates corresponded to 16S rRNA type II. Pulsed-field gel electrophoresis (PFGE) analysis revealed seven different PFGE types among the feline B. henselae strains. Interestingly, all feline isolates displayed low genetic relatedness to B. henselae strain Berlin-1, which is pathogenic for humans. (+info)
To walk or to fly? How birds choose among foraging modes.
(70/1525)
We test the predictive value of the main energetic currencies used in foraging theory using starlings that choose between two foraging modes (walking versus flying). Walking is low-cost, low-yield, whereas flying is the opposite. We fixed experimentally, at 11 different values, the amount of flight required to get one food reward, and for each flight cost value, we titrated the amount of walking until the birds showed indifference between foraging modes. We then compared the indifference points to those predicted by gross rate of gain over time, net rate of gain over time, and the ratio of gain to expenditure (efficiency). The results for the choice between modes show strong qualitative and quantitative support for net rate of gain over time over the alternatives. However, the birds foraged for only a fraction of the available time, indicating that the choice between foraging and resting could not be explained by any of these currencies. We suggest that this discrepancy could be accounted for functionally because nonenergetic factors such as predation risk may differ between resting and foraging in any mode but may not differ much between foraging modes, hence releasing the choice between foraging modes from the influence of such factors. Alternatively, the discrepancy may be attributable to the use of predictable (rather than stochastic) ratios of effort per prey in our experiment, and it may thus be better understood with mechanistic rather than functional arguments. (+info)
Widespread origins of domestic horse lineages.
(71/1525)
Domestication entails control of wild species and is generally regarded as a complex process confined to a restricted area and culture. Previous DNA sequence analyses of several domestic species have suggested only a limited number of origination events. We analyzed mitochondrial DNA (mtDNA) control region sequences of 191 domestic horses and found a high diversity of matrilines. Sequence analysis of equids from archaeological sites and late Pleistocene deposits showed that this diversity was not due to an accelerated mutation rate or an ancient domestication event. Consequently, high mtDNA sequence diversity of horses implies an unprecedented and widespread integration of matrilines and an extensive utilization and taming of wild horses. However, genetic variation at nuclear markers is partitioned among horse breeds and may reflect sex-biased dispersal and breeding. (+info)
Are avian blood parasites pathogenic in the wild? A medication experiment in blue tits (Parus caeruleus).
(72/1525)
The Hamilton and Zuk hypothesis on haemoparasite-mediated sexual selection and certain studies of reproductive costs are based on the assumption that avian blood parasite infections are detrimental to their hosts. However, there is no experimental evidence demonstrating harmful effects of blood parasites on fitness in wild populations, it even having been suggested that they may be non-pathogenic. Only an experimental manipulation of natural blood parasite loads may reveal their harmful effects. In this field experiment we reduced through medication the intensity of infection by Haemoproteus majoris and the prevalence of infection by Leucocytoazoon majoris in blue tits (Parus caeruleus), and demonstrated detrimental effects of natural levels of infection by these common parasite species on host reproductive success and condition. The fact that some of the costs of infection were paid by offspring indicates that blood parasites reduce parental working capacity while feeding nestlings. Medicated females may be able to devote more resources to parental care through being released from the drain imposed upon them by parasites and/or through a reduced allocation to an immune response. Therefore, this work adds support to previous findings relating hosts' life-history traits and haematozoan infections. (+info)