40 resultados para Reproduction.
Resumo:
1. Freshwater unionoids are one of the most threatened animal groups worldwide and the freshwater pearl mussel Margaritifera margaritifera is currently listed as critically endangered in Europe. The ‘EC Habitats & Species Directive’ requires that EU member states monitor the distribution and abundance of this species and report regularly on its conservation status.
2. The pearl mussel meta-population in Northern Ireland was surveyed to assess temporal population trends in Special Areas of Conservation (SACs) and mussel reproduction throughout its range.
3. Mussels occurred in six rivers and numbers within three SAC designated sites remained stable between 2004-07 and 2011. The discovery of >8,000 previously unknown individuals in the Owenreagh River contributed to an overall increase (+56.8%) in the total known population. All populations actively reproduced during 2010 with approximately half of all individuals gravid. Moreover, suitable salmonid hosts occurred at all sites with 10.7% of salmon and 22.8% of trout carrying encysted glochidia. Populations were composed entirely of aged individuals with little evidence of recent recruitment.
4. We infer that the break in the life cycle must occur during the juvenile stage when glochidia metamorphose and settle into the interstitial spaces within the substrate. Water quality parameters, most notably levels of suspended solids, exceeded the recommended maximum thresholds in all rivers.
5. We posit that the deposition of silt may be the main cause of juvenile mortality contributing to a lack of recruitment. Consequently, all populations were judged to be in ‘unfavourable’ conservation status. Catchment-level management plans are urgently needed to reduce siltation with the aim of improving recruitment. Our results have implications for the success of ex-situ conservation programmes; specifically, the size at which captive bred juveniles are released into the wild. Further research is required to assess the vulnerabilities of early life stages of M. margaritifera to siltation.
Resumo:
How are resources split between caring for offspring and self-maintenance? Is the timing of immune challenge important? In burying beetles challenging the immune system prior to breeding does not affect the total number and quality of offspring produced during the individual's lifetime. However, the immune system is suppressed during breeding and if an immune challenge is presented during this time the beetle will upregulate its immune system, but at the detriment to the number of offspring produced during that breeding opportunity.We know that parental investment and immune investment are costly processes, but it is unclear which trait will be prioritized when both may be required. Here, we address this question using the burying beetle Nicrophorus vespilloides, carrion breeders that exhibit biparental care of young. Our results show that immunosuppression occurs during provision of parental care. We measured phenoloxidase (PO) on Days 1-8 of the breeding bout and results show a clear decrease in PO immediately from presentation of the breeding resource onward. Having established baseline immune investment during breeding we then manipulated immune investment at different times by applying a wounding challenge. Beetles were wounded prior to and during the parental care period and reproductive investment quantified. Different effects on reproductive output occur depending on the timing of wounding. Challenging the immune system with wounding prior to breeding does not affect reproductive output and subsequent lifetime reproductive success (LRS). LRS is also unaffected by applying an immune elicitor prior to breeding, though different arms of the immune system are up/downregulated, perhaps indicating a trade-off between cellular and humoral immunity. In contrast, wounding during breeding reduces reproductive output and to the greatest extent if the challenge is applied early in the breeding bout. Despite being immunosuppressed, breeding beetles can still respond to wounding by increasing PO, albeit not to prebreeding levels. This upregulation of PO during breeding may affect parental investment, resulting in a reduction in reproductive output. The potential role of juvenile hormone in controlling this trade-off is discussed.
Resumo:
While feminist scholarship has centred reproduction in women’s lives, it has inadequately explored its meanings in men’s. If we assume that reproduction happens in relationships of one kind or another between males and females, then missing men is a considerable oversight. Although there is now much research on fatherhood,merely focussing on this end-stage assumes that women take care of all of the foreplay, leaving unanswered questions in relation, inter alia, to men’s desires for parenthood,men’s involvement in planning or lack of planning to have children, the way men struggle or cope with infertility, their encounters with new reproductive technologies and surrogate mothers, their experiences of foetal screening, their involvement in abortion decision-making, and their experiences of becoming or not becoming a father. In this article I argue that men have compelling experiences throughout the reproductive trajectory deserving of more attention. I offer a profeminist theoretical composition for advancing further enquiries on men and reproduction,which begins with the feminism-informed Critical Studies of Men and Masculinities (CSM), and then weaves this together with the theories of intimate citizenship, sociology of the body, and the sociology of science and technology. I will propose how concepts from these collective theories may be useful in opening up layered questions about gender relations, intimacy, bodies, and technologies in future studies of men and reproduction.
Resumo:
Due to its efficiency and simplicity, the finite-difference time-domain method is becoming a popular choice for solving wideband, transient problems in various fields of acoustics. So far, the issue of extracting a binaural response from finite difference simulations has only been discussed in the context of embedding a listener geometry in the grid. In this paper, we propose and study a method for binaural response rendering based on a spatial decomposition of the sound field. The finite difference grid is locally sampled using a volumetric array of receivers, from which a plane wave density function is computed and integrated with free-field head related transfer functions, in the spherical harmonics domain. The volumetric array is studied in terms of numerical robustness and spatial aliasing. Analytic formulas that predict the performance of the array are developed, facilitating spatial resolution analysis and numerical binaural response analysis for a number of finite difference schemes. Particular emphasis is placed on the effects of numerical dispersion on array processing and on the resulting binaural responses. Our method is compared to a binaural simulation based on the image method. Results indicate good spatial and temporal agreement between the two methods.
Resumo:
Neoliberal capitalism and its accompanied austerity measures has had a profound effect on social reproduction throughout Europe. Social reproduction, ie, the process that makes it possible for individuals, families, and society to reproduce itself – is in crisis. The concept of social reproduction utilized in this presentation is framed within the feminist and Marxist tradition. Historically, social reproduction was met through both waged and unwaged work with women playing a predominant role either as waged, predominantly public sector, workers (social workers, teachers, carers, nurses, etc) or as unpaid workers (unpaid carers: mothers, wives, etc.) but now both forms of work are destabilized and undermined. Thus, the crisis in social reproduction. Within this crisis women’s unequal position is further undermined but at the same time progressive women and men are organizing to present alternatives forms of social reproduction. This presentation by utilizing the case of Greece will first outline the neoliberal processes that have caused the crisis in social reproduction. Second, it will present the consequences of social reproduction by highlighting the gender implications. Third, it will discuss the reorganization of social reproduction which is taking place outside the logic of capitalist society and is manifested through the creation of solidarity health clinics and pharmacies, communal kitchens, creation of various forms of bartering etc. This presentation will argue that these forms present glimpses of another society , a society based on principles of solidarity and cooperation. A society worth fighting for. And finally the presentation will conclude by discussing at which level can this crisis be resolved and the role of the social work profession.