Adaptive female choice for middle-aged mates in a lekking sandfly

Most theoretical models of age-related mate choice predict that females should prefer older males because they have proven survival ability. An alternative view is that older males represent inferior mates because of negative genetic correlations between early and late fitness components, or because older males have traded off longevity against other fitness components, have accumulated deleterious germ-line mutations, or are less well adapted to current conditions than more recently born individuals. While numerous studies have reported female choice for older males, few have explicitly examined the fitness consequences of such a preference. We present evidence from a lekking sandfly, Lutzomyia longipalpis , showing that choosy females discriminate against older males and gain a fitness benefit from their choice. When permitted free choice from an aggregation consisting of males aged zero to two days (young), four to six days (middle-aged) and eight to ten days (old), females preferentially mated with middle-aged males, but all measures of female reproductive success were independent of male age. In contrast, when a second set of females was randomly assigned single virgin males of known age, the eggs of those paired to old mates exhibited lower hatching success than the eggs of females mated to young or middle-aged males. These results suggest that females avoid mating with older males because they represent poorer quality mates. Age-related differences in male quality may have a genetic basis, but could equally well arise through a phenotypic decline in sperm quality or sperm transfer ability with male age. The lack of evidence of female discrimination against older males from other studies may be because these did not explore the reproductive success of the full age range of males

Becoming a networked researcher: using social media for research and researcher development

Unable to conduct PhD fieldwork overseas, Dr Sarah-Louise Quinnell found herself searching for new ways to communicate with actors dispersed across the globe. Now, her website, a virtual research environment, has become the hub of her research and she utilises forums, blogs and twitter to interact with more actors and increase her impact through different audiences

The epidemiology of canine leishmaniasis: transmission rates estimated from a cohort study in Amazonian Brazil

We estimate the incidence rate, serological conversion rate and basic case reproduction number (R0) of Leishmania infantum from a cohort study of 126 domestic dogs exposed to natural infection rates over 2 years on Marajó Island, Pará State, Brazil. The analysis includes new methods for (1) determining the number of seropositives in cross-sectional serological data, (2) identifying seroconversions in longitudinal studies, based on both the number of antibody units and their rate of change through time, (3) estimating incidence and serological pre-patent periods and (4) calculating R0 for a potentially fatal, vector-borne disease under seasonal transmission. Longitudinal and cross-sectional serological (ELISA) analyses gave similar estimates of the proportion of dogs positive. However, longitudinal analysis allowed the calculation of pre-patent periods, and hence the more accurate estimation of incidence: an infection–conversion model fitted by maximum likelihood to serological data yielded seasonally varying per capita incidence rates with a mean of 8·66×10[minus sign]3/day (mean time to infection 115 days, 95% C.L. 107–126 days), and a median pre-patent period of 94 (95% C.L. 82–111) days. These results were used in conjunction with theory and dog demographic data to estimate the basic reproduction number, R0, as 5·9 (95% C.L. 4·4–7·4). R0 is a determinant of the scale of the leishmaniasis control problem, and we comment on the options for control

Rapid Detection of Leishmania infantum Infection in Dogs: Comparative Study Using an Immunochromatographic Dipstick Test, Enzyme-Linked Immunosorbent Assay, and PCR

Current zoonotic visceral leishmaniasis (ZVL) control programs in Brazil include the culling of Leishmania infantum-infected reservoir dogs, a strategy that has failed to prevent a rise of canine and human ZVL cases over the past decade. One of the main reasons this strategy has failed is because of a long delay between sample collection, sample analysis, and control implementation. A rapid, sensitive, and specific diagnostic tool would be highly desirable, because it would allow control interventions to be implemented in situ. We compared an immunochromatographic dipstick test to enzyme-linked immunosorbent assay (ELISA) and PCR for detecting L. infantum infections in dogs from an area of ZVL endemicity in Brazil. The dipstick test was shown to have 61 to 75% specificity and 72 to 77% sensitivity, compared to 100% specificity for both ELISA and PCR and 71 to 88% and 51 to 64% sensitivity for ELISA and PCR, respectively. Of the field samples tested, 92 of 175 (53%), 65 of 175 (37%), and 47 of 175 (27%) were positive by dipstick, ELISA, and PCR, respectively. The positive and negative predictive values for the tested dipstick were 58 to 77% and 75%, respectively. Efforts should be made to develop a more specific dipstick test for diagnosis of leishmaniasis, because they may ultimately prove more cost-effective than currently used diagnostic tests when used in mass-screening surveys

Ophelia

Poem by Mary M. Quinnell

Prophecy

Poem by M.M. Quinnell

Immune Responses in Human Necatoriasis: Association between Interleukin-5 Responses and Resistance to Reinfection

Cytokine and proliferative responses to Necator americanus infection were measured in a treatment-reinfection study of infected subjects from an area of Papua New Guinea where N. americanus is highly endemic. Before treatment, most subjects produced detectable interleukin (IL)4 (97%), IL-5 (86%), and interferon (IFN)-γ(64%) in response to adult N. americanus antigen. Pretreatment IFN-γ responses were negatively associated with hookworm burden, decreasing by 18 pg/mL for each increase of 1000 eggs/gram (epg) (n = 75; P < .01). Mean IFN-γ responses increased significantly after anthelmintic treatment, from 166 to 322 pg/mL (n = 42; P < .01). The intensity of reinfection was significantly negatively correlated with pretreatment IL-5 responses, decreasing by 551 epg for each 100 pg/mL increase in production of IL-5 (n = 51; P < .01). These data indicate that there is a mixed cytokine response in necatoriasis, with worm burdenassociated suppression of IFN-γ responses to adult N. americanus antigen. Resistance to reinfection is associated with the parasite-specific IL-5 response

Infectiousness in a Cohort of Brazilian Dogs: Why Culling Fails to Control Visceral Leishmaniasis in Areas of High Transmission

The elimination of seropositive dogs in Brazil has been used to control zoonotic visceral leishmaniasis but with little success. To elucidate the reasons for this, the infectiousness of 50 sentinel dogs exposed to natural Leishmania chagasi infection was assessed through time by xenodiagnosis with the sandfly vector, Lutzomyia longipalpis. Eighteen (43%) of 42 infected dogs became infectious after a median of 333 days in the field (105 days after seroconversion). Seven highly infectious dogs (17%) accounted for >80% of sandfly infections. There were positive correlations between infectiousness and anti-Leishmania immunoglobulin G, parasite detection by polymerase chain reaction, and clinical disease (logistic regression, r2 = 0.080.18). The sensitivity of enzyme-linked immunosorbent assay to detect currently infectious dogs was high (96%) but lower in the latent period (<63%), and specificity was low (24%). Mathematical modeling suggests that culling programs fail because of high incidence of infection and infectiousness, the insensitivity of the diagnostic test to detect infectious dogs, and time delays between diagnosis and culling

The effect of host heterogeneity and parasite intragenomic interactions on parasite population structure

Understanding the processes that shape the genetic structure of parasite populations and the functional consequences of different parasite genotypes is critical for our ability to predict how an infection can spread through a host population and for the design of effective vaccines to combat infection and disease. Here, we examine how the genetic structure of parasite populations responds to host genetic heterogeneity. We consider the well-characterized molecular specificity of major histocompatibility complex binding of antigenic peptides to derive deterministic and stochastic models. We use these models to ask, firstly, what conditions favour the evolution of generalist parasite genotypes versus specialist parasite genotypes? Secondly, can parasite genotypes coexist in a population? We find that intragenomic interactions between parasite loci encoding antigenic peptides are pivotal in determining the outcome of evolution. Where parasite loci interact synergistically (i.e. the recognition of additional antigenic peptides has a disproportionately large effect on parasite fitness), generalist parasite genotypes are favoured. Where parasite loci act multiplicatively (have independent effects on fitness) or antagonistically (have diminishing effects on parasite fitness), specialist parasite genotypes are favoured. A key finding is that polymorphism is not stable and that, with respect to functionally important antigenic peptides, parasite populations are dominated by a single genotype

Approaches to study and conceptions of biology: Differential outcomes for generalist and vocational degree students

KEYWORDS: learning in biology, vocational learning, generalist science degree, Learner Profiling BACKGROUND: Students have diverse learning styles and a raft of instruments have been created and validated to examine learner characteristics such as approaches to study (Biggs, 1987; Biggs, Kember & Leung, 2001) and conception of discipline in various science-based courses, including maths (Crawford, Gordon, Nicholas & Prosser, 1998), physics (Prosser, Trigwell, Hazel & Waterhouse, 2000) and biology (Quinnell, May, Peat & Taylor, 2005). Student survey response data can be analysed statistically in a number of ways: for example, students returning similar responses (i.e. students who adopt similar orchestrations) can be characterised using hierarchical cluster analysis (see Trigwell, Hazel & Prosser, 1996; Trigwell Prosser & Waterhouse, 1999; Prosser et al., 2000). Such analysis has allowed us to monitor changes in these learning orchestrations over the course of a semester by extending the work of Prosser et al. (2000) and employing sequential hierarchical cluster analyses in a process we refer to as ‘Learner Profiling’ (Quinnell, May & Peat, 2012). We have demonstrated that 48% of students in an introductory university biology course changed their learning orchestrations from the start to the end of their first semester at university, with some orchestrations being more persistent than others (Quinnell et al., 2012). Biology, like other enabling science courses at first year level, involves service teaching to some extent, and we were interested to see whether students enrolled in vocational or professional degrees engaged with our curriculum differently from students enrolled in generalist degrees. With this in mind we are beginning to explore the notion of differences in learning agendas of our students and if this has an impact on how students engage with our biology curriculum. AIM: Our aim was to evaluate our learner profiling method as a means to inform curriculum design which must, by necessity, be suitable for students across a broad range of degree programs, i.e. generalist and vocational degrees. DESIGN AND METHODS: We profiled biology students as described previously (Quinnell et al., 2012) and employed post-hoc analyses to see how elements of the curriculum (good teaching, clear goals, independence, assessment, workload; as defined by Ramsden, 1991) correlate with the changes in Learner Profile. We also identified students are ‘generalist’ or ‘vocational’ based on their degree program. RESULTS: Interestingly, although perhaps not surprisingly, students enrolled in generalist degrees demonstrated greater engagement with our biology curriculum than those enrolled in vocational degrees. Our data provide some evidence that our curriculum: 1. supports generalist degree students whose conception of biology is sound and whose study approach is intrinsic, 2. is less than ideal for meeting the needs of students in vocational degrees, and 3. has failed to engage students who demonstrated dissonance at the start of semester. CONCLUSIONS: Our findings suggest that a course in biology literacy would be more suitable to students in vocational degrees and a course that is biology content-rich would suit our generalist-degree students. REFERENCES: Biggs, J. (1987). Student approaches to learning and studying. Melbourne, Australian Council for Educational Research. Biggs, J., Kember D., & Leung D. Y. P. (2001). The revised two-factor Study Process Questionnaire: R-SPQ-2F. British Journal of Educational Psychology 71: 133-149. Crawford, K., Gordon, S., Nicholas, J., & Prosser, M. (1988). Qualitatively different experiences of learning mathematics at university. Learning and Instruction, 8, 455–468. Prosser, M., Trigwell, K., Hazel, E., & Waterhouse, F. (2000). Students’ experiences of studying physics concepts: the effects of disintegrated perceptions and approaches, European Journal of Psychology of Education, 15, 61-74. Quinnell, R., May, E., & Peat, M. (2012). Conceptions of Biology and Approaches to Learning of First Year Biology Students: Introducing a technique for tracking changes in learner profiles over time. International Journal of Science Education, 34(7), 1053-1074. Quinnell, R., May, E., Peat, M., & Taylor, C. (2005). Creating a reliable instrument to assess students’ conceptions of studying biology at tertiary level. Proceedings of the Uniserve Science Conference: Blended Learning in Science Teaching and Learning, 30 September 2005 (pp. 87-92) Sydney: Uniserve Science, The University of Sydney. http://science.uniserve.edu.au/pubs/procs/wshop10/2005Quinnell.pdf Ramsden, P. (1991). A performance indicator of teaching quality in Higher Education: The Course Experience Questionnaire. Studies in Higher Education, 16(2), 129-150. Trigwell, K., Hazel, E., & Prosser, M. (1996). Perceptions of the learning environment and approaches to learning university science at the topic level. Different Approaches: Theory and Practice in Higher Education. Proceedings HERDSA Conference 1996. Perth, Western Australia, 8-12 July. (Retrieved 24 March 2011 from http://www.herdsa.org.au/confs/1996/trigwell2.html) Trigwell, K., Prosser, M., & Waterhouse F. (1999). Relations between teachers' approaches to teaching and students' approaches to learning. Higher Education, 37(1), 57-70