Binomial sampling for pest management of stable flies (Diptera: Muscidae) that attack dairy cattle.

A binomial sampling plan for pest management of the stable fly, Stomoxys calcitrans (L.), was developed. Counts of stable flies on front legs of the same animal were independent and each leg from the same animal was considered a sample unit. The relationship between the mean number of flies per leg and the variance was determined and did not vary among farms. The relationship between the mean number of flies per leg and the proportion of legs with zero, one or less, and two or less flies (P0, P1, and P2) was determined and used as the basis of the binomial sampling plan. Predicted values of the mean number of flies per leg from P0, P1, and P2 were close to observed values of the mean number of flies per leg. Equations are presented for calculating the variance of a predicted value of the mean number of flies per leg using values of P0, P1 and P2 determined by sampling. Operating characteristic (OC) curves are also presented for determining the probability of making a treatment decision error at an economic threshold of one fly per leg (P0 = 0.47) using binomial sampling or direct counting. OC curves for binomial sampling with n = 50 legs were close to those for direct counting with n = 10 legs. Recommendations concerning the use of binomial sampling for stable flies are presented.     

Altered mandibular development precedes the time of palate closure in mice homozygous for disproportionate micromelia: an oral clefting model supporting the Pierre-Robin sequence

BACKGROUND: Development of the human craniofacial anatomy involves a number of interrelated, genetically controlled components. The complexity of the interactions between these components suggests that interference with the spaciotemporal interaction of the expanding tongue and elongating Meckel's cartilage correlates with the appearance of cleft palate. Mice homozygous for the semi-dominant Col2a1 mutation Disproportionate micromelia (Dmm), presenting at birth with both cleft palate and micrognathia, provide the opportunity to test the hypothesis that mandibular growth retardation coincides with formation of the secondary palate as predicted from our understanding of the Pierre Robin sequence. The present study was conducted in embryonic day 14 (E14) mice, 1 day before palate closure, to describe the relationship between growth of the lower jaw/tongue complex versus genotype of the embryo. METHODS: Whole heads, isolated from E14.25, E14.5 and E14.75 wild-type and homozygous mutant embryos, were fixed in Bouin's solution, embedded in paraffin, and serially sectioned. Mid-sagittal sections, stained with toluidine blue, were used to estimate growth of both tongue and lower jaw (Meckel's cartilage length) during a 12-hr period preceding palate closure. RESULTS: In control embryos, the largest increase in Meckel's cartilage length occurred between E14.5 and E14.75. Compared to control, the mean Meckel's cartilage length in the mutant was similar at E14.25, but was significantly less at E14.5 and E14.75. Absolute tongue size in control embryos increased linearly during this period of E14.25 to E14.75. Relative to the rapidly growing Meckel's cartilage, however, relative tongue size in control embryos actually decreased over time. Absolute tongue size in the mutant was not significantly different from that of control at any of the embryonic stages examined, however, relative tongue size in the mutant was significantly greater at E14.75 compared to control. CONCLUSION: Mandibular growth retardation, coupled with relative macroglossia in E14 Dmm/Dmm mice, suggests that the concerted development of the palate and lower jaw complex in the mutant is aberrant. Detection of micrognathia and pseudomacroglossia in homozygotes, before the time of palate closure, supports the hypothesis that a relationship exists between growth retardation of Meckel's cartilage and malformation of the secondary palate, as predicted by the Pierre-Robin sequence.     

Can separation along the temperature niche axis promote coexistence between native and invasive species?

Aim Western mosquitofish (Gambusia affinis) have been linked with the decline of native fish and amphibians throughout the world. Separation along the temperature niche axis may promote the long‐term coexistence of introduced western mosquitofish, with native species in temperate regions. Recent research has shown that western mosquitofish can reduce the recruitment of native least chub (Iothichthys phlegethontis) endemic to the Bonneville Basin. We tested the hypotheses that cold temperatures (≤ 15 °C in the summer, freezing winters) would: (1) reduce the aggressive and predatory effects of western mosquitofish on least chub, and (2) eliminate the overwinter survival and recruitment of western mosquitofish while having little effect on least chub recruitment. Location Bonneville Basin of Utah, USA. Methods We used short‐term tests in the laboratory at the level of individuals and manipulated temperature (warm, cold and seasonal treatments) in long‐term experiments using mesocosms at the population level. Results Cold temperatures (≤ 15 °C) reduced the aggression and predation of western mosquitofish on least chub at the level of individuals. At the population level, however, cool summers (≤ 15 °C) eliminated recruitment in both species because they required warm summers (c. 20–30 °C) to survive freezing winters. Although least chub had an overwinter advantage in survival (75% least chub, 45% western mosquitofish), it was overwhelmed by the rapid reproduction of western mosquitofish as temperatures increased in the summer. Main conclusions Studies at the level of populations are necessary to understand the ultimate effects of introduced species on native taxa. Separation along the temperature niche axis was not sufficient to promote coexistence between these species in habitats with warm summers (c. 30 °C). Although coexistence may be possible in habitats with cool summers (≤ 20 °C) and freezing winters, the ability of niche separation to promote long‐term coexistence between native and introduced species may ultimately depend on their respective rates of evolution. Long‐term coexistence may not be possible if introduced species can adapt to new environmental conditions faster than native species can evolve mechanisms to reduce their harmful effects.     

Barley response to nitrogen and non-nutritional benefits of legume green manure

Green manure application may benefit subsequent crops not only by improving nitrogen (N) fertility but also via non-nutritional mechanisms. The quantification of the latter effect, however, is complicated by the confounding effect of N fertility. Two experiments were conducted in controlled environments to partition the yield response of barley to green manure between N and non-nutritional effects. Each experiment included a factorial of fertilizer N application rates and green manure application rates. The fertilizer was labelled with ¹⁵N to facilitate discrimination between N sources. Approximately 24% of the N applied in green manure was assimilated by barley after 45 days (Experiment 1) and 32% was recovered by barley grown to maturity (Experiment 2). Apparent recovery of green manure-N by barley was not appreciably affected by fertilizer application. Regression analysis of the relationship between dry matter yield and plant N uptake demonstrated that yield responses to green manure application were not entirely attributable to improved N fertility. For a given amount of N assimilated by the crop, yields were higher in green manure-amended treatments than in those receiving no green manure. In barley grown to maturity, barley response to N and non-nutritional effects were estimated to be 5.3 and 2.2g pot⁻¹, respectively. The relationship between dry matter yield and N uptake is suggested as a method for distinguishing nutritional and non-nutritional yield responses. This approach assumes that no other nutrient is limiting growth. The presence of non-nutritional benefits observed in this study demonstrates that the agronomic value of green manure is not limited to N release and casts doubt on the assumptions inherent to calculation of fertilizer equivalents. Contribution 3879132 Contribution 3879132     

Statistical Analysis of the Comet Assay Using a Mixture of Gamma Distributions

Tail moments in the single cell gel electrophoresis (comet) assay usually do not follow a normal distribution, making the statistical analysis complicated. Researchers have used a wide variety of statistical techniques in an attempt to overcome this problem. In many cases, the tail moments follow a bimodal distribution that can be modeled with a mixture of gamma distributions. This bimodality may be due to cells being in two different stages of the cell cycle at the time of treatment. Maximum likelihood, modified to accommodate censored data, can be used to estimate the five parameters of the gamma mixture distribution for each slide. A weighted analysis of variance on the parameter estimates for the gamma mixtures can be performed to determine differences in DNA damage between treatments. These methods were applied to an experiment on the effect of thymidine kinase in DNA damage and repair. Analysis based on the mixture of gamma distributions was found to be more statistically valid, more powerful, and more informative than analysis based on log-transformed tail moments.