Early exposure to UV radiation causes telomere shortening and poorer condition later in life

Determining the contribution of elevated ultraviolet–B radiation (UVBR; 280 — 315 nm) to amphibian population declines is being hindered by a lack of knowledge about how different acute UVBR exposure regimes during early life history stages might affect post–metamorphic stages via long–term carryover effects. We acutely exposed tadpoles of the Australian green tree frog (Litoria caerulea) to a combination of different UVBR irradiances and doses in a multi–factorial experiment, and then reared them to metamorphosis in the absence of UVBR to assess carryover effects in subsequent juvenile frogs. Dose and irradiance of acute UVBR exposure influenced carryover effects into metamorphosis in somewhat opposing manners. Higher doses of UVBR exposure in larvae yielded improved rates of metamorphosis. However, exposure at a high irradiance resulted in frogs metamorphosing smaller in size and in poorer condition than frogs exposed to low and medium irradiance UVBR as larvae. We also demonstrate some of the first empirical evidence of UVBR-induced telomere shortening in vivo, which is one possible mechanism for life–history trade–offs impacting condition post-metamorphosis. These findings contribute to our understanding of how acute UVBR exposure regimes in early life affect later life–history stages, which has implications for how this stressor may shape population dynamics.

Interactions of Feelings of Competence and Motivation of Pre-Service Science Teachers in Their Laboratory Course: A Dynamic Multilevel Modeling Approach

Dynamic structural equation modeling was applied to examine feelings of competence and in the moment motivation among pre-service science teachers (N = 101) enrolled in a course on practical biology during their second semester. The student teachers completed a short questionnaire 18 times, and the interaction between their feelings of competence and momentary motivation over time was examined in relation to control-value theory. The autoregressive values of both variables were significant, and a pattern was observed of low competence at the beginning of the course session, combined with low motivation in the moment. Feelings of competence increased by the end of each course session but returned to a low level at the beginning of the next session. Momentary motivation followed this back-and-forth shifting somewhat but showed more carryover effects. The student teachers’ motivation depended on their feelings of competence from the previous moment in the biology course session, but feelings of competence did not depend on their motivation.

Past insecticide exposure reduces bee reproduction and population growth rate

Pesticides are linked to global insect declines, with impacts on biodiversity and essential ecosystem services. In addition to well-documented direct impacts of pesticides at the current stage or time, potential delayed “carryover” effects from past exposure at a different life stage may augment impacts on individuals and populations. We investigated the effects of current exposure and the carryover effects of past insecticide exposure on the individual vital rates and population growth of the solitary bee, Osmia lignaria. Bees in flight cages freely foraged on wildflowers, some treated with the common insecticide, imidacloprid, in a fully crossed design over 2 y, with insecticide exposure or no exposure in each year. Insecticide exposure directly to foraging adults and via carryover effects from past exposure reduced reproduction. Repeated exposure across 2 y additively impaired individual performance, leading to a nearly fourfold reduction in bee population growth. Exposure to even a single insecticide application can have persistent effects on vital rates and can reduce population growth for multiple generations. Carryover effects had profound implications for population persistence and must be considered in risk assessment, conservation, and management decisions for pollinators to mitigate the effects of insecticide exposure.

On MSE-Optimal Circular Crossover Designs

In crossover designs, each subject receives a series of treatments, one after the other in p consecutive periods. There is concern that the measurement of a subject at a given period might be influenced not only by the direct effect of the current treatment but also by a carryover effect of the treatment applied in the preceding period. Sometimes, the periods of a crossover design are arranged in a circular structure. Before the first period of the experiment itself, there is a run-in period, in which each subject receives the treatment it will receive again in the last period. No measurements are taken during the run-in period. We consider the estimate for direct effects of treatments which is not corrected for carryover effects. If there are carryover effects, this uncorrected estimate will be biased. In that situation, the quality of the estimate can be measured by the mean square error, the sum of the squared bias and the variance. We determine MSE-optimal designs, that is, designs for which the mean square error is as small as possible. Since the optimal design will in general depend on the size of the carryover effects, we also determine the efficiency of some designs compared to the locally optimal design. It turns out that circular neighbour-balanced designs are highly efficient.

Long-Term and Carryover Effects of Supplementation with Whole Oilseeds on Methane Emission, Milk Production and Milk Fatty Acid Profile of Grazing Dairy Cows

Research is ongoing to find nutritional methane (CH4) mitigation strategies with persistent effects that can be applied to grazing ruminants. Lipid addition to dairy cow diets has shown potential as means to decrease CH4 emissions. This study evaluated the effects of oilseeds on CH4 emission and production performance of grazing lactating dairy cows. Sixty Holstein Friesian cows grazing pasture were randomly allocated to 1 of 4 treatments (n = 15): supplemented with concentrate without oilseeds (CON), with whole cottonseed (CTS), rapeseed (RPS) or linseed (LNS). Oilseeds were supplemented during weeks 1–16 (spring period) and 17–22 (summer period), and the autumn period (wk 23–27) was used to evaluate treatment carryover effects. Cows fed CTS decreased CH4 yield by 14% compared to CON in spring, but these effects did not persist after 19 weeks of supplementation (summer). Compared to CON, RPS decreased milk yield and CTS increased milk fat concentration in both spring and summer. In summer, CTS also increased milk protein concentration but decreased milk yield, compared to CON. In spring, compared to CON, CTS decreased most milk medium-chain fatty acids (FA; 8:0, 12:0, 14:0 and 15:0) and increased stearic, linoleic and rumenic FA, and LNS increased CLA FA. There were no carry-over effects into the autumn period. In conclusion, supplementation of grazing dairy cows with whole oilseeds resulted in mild effects on methane emissions and animal performance. In particular, supplementing with CTS can decrease CH4 yield without affecting milk production, albeit with a mild and transient CH4 decrease effect. Long term studies conducted under grazing conditions are important to provide a comprehensive overview of how proposed nutritional CH4 mitigation strategies affect productivity, sustainability and consumer health aspects.

Bayesian Analysis of an Optimal Five Period Cross-over Design

A crossover design is a repeated measurements design such that each experimental unit receives different treatments during the different time periods. In a majority of bioequivalence studies, design and analysis of cross-over using classical methods such as analysis of variance (ANOVA) and test are normally associated with erroneous results. The Bayesian method is desirable in the analysis of crossover designs to eliminate errors associated with carryover effects. The objective of this study was to compare the Bayesian and the - test analysis methods on treatments and carryover effects for an optimal two treatments, five periods and four sequence C (2, 5, 4) design. The treatments and residual estimates were obtained using Best Linear Unbiased Estimation (BLUE) method. In the Bayesian method of analysis, the posterior quantities were obtained for the mean intervals of treatments and carry-over effects and the highest posterior density (HPD) graphs were plotted and interpreted using conditional probability statements. For validation purposes, the Bayesian method results were compared with the existing -tests results. From the Bayesian analysis, the probability of significant treatment difference in the presence of carryover effects was 1, while from the -test, the calculated value of 11.73 was greater than the two sided tabulated value at 95 level of significance. The two analysis methods implied significant differences in the treatment effects. In conclusion, it was established that Bayesian method of analysis can be used for bioequivalence analysis even when the carry-over effects are present and hence it is highly recommended for bioequivalence studies.