Environmentally sustainable pest control options for Drosophila suzukii

The spotted‐wing drosophila or cherry vinegar fly (Drosophila suzukii) is native to Asia but has invaded other continents since 2008 and has spread throughout Europe. The females have a serrated ovipositor allowing them to penetrate the skins of intact ripening fruits to deposit their eggs, and the developing larvae rapidly destroy the fruits close to harvest. Drosophila suzukii has a rapid life cycle and the larvae develop well beneath the fruit surface. This means that the use of pesticides is problematic and often not effective, first due to their restricted use close to harvest to protect consumers, and second because the larvae are deep enough inside the fruit to avoid contact. There are currently no effective and environmentally sustainable pest control methods for this species, resulting in extensive damage to fruit crops. Here, we review the current status of D. suzukii as a fruit crop pest and discuss the feasibility of current pesticide‐free control methods. We also consider the potential of new technologies as a basis for the urgently needed specific and long‐term control of this species.     

Evaluation of yeasts in gel larval diet for Queensland fruit fly,Bactrocera tryoni

Queensland fruit fly, Bactrocera tryoni (“Q‐fly”), is Australia’s most economically important insect pest of horticultural and commercial crops especially in the eastern regions. The sterile insect technique (SIT) has been adopted as an environmentally benign and sustainable approach for management of Q‐fly outbreaks. High‐performance larval diets are required to produce the millions of flies needed each week for SIT. Yeast products contribute amino acids (protein) to fruit fly larval diets, as well as carbohydrate, fat and micronutrients, but there can be substantial variation in the nutritional composition and suitability of yeast products for use in larval diets. Gel larval diets have recently been developed for large‐scale rearing of Q‐fly for SIT, and composition of these diets requires optimization for both performance and cost, including choice of yeast products. We assessed performance of Q‐flies reared on gel larval diets that contained debittered brewer’s yeast (Lallemand LBI2240), hydrolysed yeast (Lallemand FNILS65), inactivated brewer’s yeast (Lallemand LBI2250) and inactivated torula yeast (Lallemand 2160‐50), including blends. Q‐flies performed poorly when reared on diets containing only or mostly hydrolysed yeast in terms of pupal number, pupal weight and percentage of fliers. Performance was also poor on diets containing high proportions of torula yeast. Overall, debittered brewer’s yeast is recommended as the best option for Q‐fly gel larval diet, as it is cheap, readily available, and produces flies with good performance in quality control assays. Inactivated brewer’s yeast produced flies of comparable quality with only a modest increase in cost and would also serve as an effective alternative.     

Reconciling variability and optimal behaviour using multiple criteria in optimization models

A major objective in behavioural and evolutionary ecology is to understand how animals make decisions in complex environments. Examinations of animal behaviour typically use optimization models to predict the choices animals ought to make. The performance of animals under specific conditions is then compared against the predicted optimal strategy. This optimization approach has come into question because model predictions often do not match animal behaviour exactly. This has led to serious scepticism about the ability of animals to exhibit optimal behaviour in complex environments. We show that conventional approaches that compare observed animal behaviour with single optimal values may bias the way we view real-world variation in animal performance. Considerable insight into the abilities of animals to make optimal decisions can be gained by interpreting why variability in performance exists. We introduce a new theoretical framework, called multi-objective optimization, which allows us to examine decision-making in complex environments and interpret the meaning of variability in animal performance. A multi-objective approach defines the set of efficient choices animals may make in attempting to reach compromises among multiple conflicting demands. In a multi-objective framework, we may see variation in animal choices, but, unlike single-objective optimizations where there is one best solution, this variation may represent a range of adaptive compromises to conflicting objectives. An important feature of this approach is that, within the set of efficient alternatives, no choice can be considered to yield higher fitness, a priori, than any other choice. Thus, variability and optimal behaviour may be entirely consistent. We illustrate our point using selected examples from foraging theory where there is already an optimization program in place.     

NMR analysis of carbohydrates with model-free spectral densities: the dispersion range revisited

Over the past decade molecular mechanics and molecular dynamics studies have demonstrated considerable flexibility for carbohydrates. In order to interpret the corresponding NMR parameters, which correspond to a time-averaged or 'virtual' conformer, it is necessary to simulate the experimental data using the averaged geometrical representation obtained with molecular modelling methods. This structural information can be transformed into theoretical NMR data using empirical Karplus-type equations for the scalar coupling constants and the appropriate formalism for the relaxation parameters. In the case of relaxation data, the 'model-free' spectral densities have been widely used in order to account for the internal motions in sugars. Several studies have been conducted with truncated model-free spectral densities based on the assumption that internal motion is very fast with respect to overall tumbling. In this report we present experimental and theoretical evidence that suggests that this approach is not justified. Indeed, recent results show that even in the case of moderate-sized carbohydrates internal motions are occurring on the same timescale as molecular reorientation. Simulations of relaxation parameters (NOESY volumes, proton cross-relaxation rates, carbon T1 and nOe values) in the dispersion range (0.1<Tc<5 ns) show that rates of internal motion can be fairly precisely defined with respect to overall tumbling. Experimental data for a variety of oligosaccharides clearly indicate similar timescales for internal and overall motion. This revised version was published online in August 2006 with corrections to the Cover Date.     

Conformational analysis of methyl 6-O-[(R)- and (S)-1-carboxyethyl]-α-D-galactopyranoside by MM and Langevin dynamics simulations

The conformational space of methyl 6-O-[(R)- and (S)- 1-carboxyethyl]-α-D-galactopyranoside has been investigated. A grid search employing energy minimization at each grid point over the three major degrees of freedom, namely φ, ψ and ω, identified low energy regions. The R-isomer shows five low energy conformers within ca. 1 kcal mol−1 of the global energy minimum. The S-isomer has two conformers within a few tenths of a kcal mol−1 of the global energy minimum. Langevin dynamics simulations have been have been performed at 300 K for 30 ns of each isomer. The φ dihedral angle has as its major conformer (g−1) for the R-isomer whereas it is the (g+) conformer for the S-isomer. For the ψ dihedral angle the (t) conformer has the highest population for both isomers. The dihedral angle ω has the (g+) conformer most highly populated, both for the R- and S-isomer. The above five and two conformational states for the R- and S-isomers, respectively, make up 90% in each case of the populated states during the Langevin dynamics (LD) simulations. Rate constants for the ω dihedral angle have been calculated based on a number correlation function. Three bond homo- and heteronuclear, i.e. proton and carbon-13, coupling constants have been calculated from the dynamics trajectories for comparison to experimental values. The heteronuclear coupling constant H2′,C6 has been measured for the S-isomer and found to be 3.3 Hz. The J value calculated from the LD simulations, namely 2.6 Hz, is in fair agreement with experiment. A comparison to the X-ray structure of the R-isomer shows that the conformation of the crystalline compound occupies the low energy region most highly populated as a single R-conformer (30%) during the LD simulations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Prediction of normal values for lactate threshold estimated by gas exchange in men and women

Lactate threshold (LT) is an index of exercise capacity and can be estimated from the gas exchange consequences of a metabolic acidosis (LT_GE). In recent years, it has emerged as a diagnostic tool in the evaluation of subjects with exercise limitation. The purpose of this study was to develop LT_GE prediction equations on a relatively large sample of adults and to cross-validate each equation. A total of 204 healthy, sedentary, nonsmoking subjects (103 men and 101 women), aged 20–70 years, underwent graded exercise testing on a cycle ergometer. The V-slope technique was used to detect LT_GE as the oxygen uptake (V˙O₂) at the breakpoint of the carbon dioxide output versus V˙O₂ relationship. Multiple linear regression was used to develop 12 equations with combinations of the following predictor variables: age, height, body mass, and fat-free mass. Eight of the equations are gender-specific and four are generalized with gender as a dummy variable. The equations were cross-validated using the predicted residual sum of squares (PRESS) method. The results demonstrate that the equations had relatively high multiple correlations (0.577–0.863) and low standard errors of the estimate (0.123–0.228 1 · min⁻¹). The PRESS method demonstrated that the equations are generalizable, i.e., can be used in future studies without a significant loss of accuracy. Since we tested only healthy, sedentary subjects, our equations can be used to predict the lower limit of normal for a given subject. Using individual data for healthy and diseased subjects from the literature, we found that our gender-specific equations rarely miscategorized subjects unless they were obese and mass was a predictor variable. We conclude that our equations provide accurate predictions of normal values for LT_GE and that they are generalizable to other subject populations. Accepted: 13 February 1997     

THE EVOLUTION OF THRESHOLD TRAITS: A QUANTITATIVE GENETIC ANALYSIS OF THE PHYSIOLOGICAL AND LIFE-HISTORY CORRELATES OF WING DIMORPHISM IN THE SAND CRICKET

Many traits are phenotypically discrete but polygenically determined. Such traits can be understood using the threshold model of quantitative genetics that posits a continuously distributed underlying trait, called the liability, and a threshold of response, individuals above the threshold displaying one morph and individuals below the threshold displaying the alternate morph. For many threshold traits the liability probably consists of a hormone or a suite of hormones. Previous experiments have implicated juvenile hormone esterase (JHE), a degratory enzyme of juvenile hormone, as a physiological determinant of wing dimorphism in the crickets Gryllus rubens and G. firmus. The present study uses a half-sib experiment to measure the heritability of JHE in the last nymphal stadium of G. firmus and its genetic correlation with fecundity, a trait that is itself genetically correlated with wing morph. The phenotypic and genetic parameters are consistent with the hypothesis that JHE is a significant component of the liability. Comparison of sire and dam estimates suggest that nonadditive effects may be important. Two models have been proposed to account for the fitness differences between morphs: the dichotomy model, which assumes that each morph can be characterized by a particular suite of traits, and the continuous model, which assumes that the associated fitness traits are correlated with the liability rather than the morphs themselves. The latter model predicts that the fitness differences will not be constant but change with the morph frequencies. Variation in fecundity and flight muscle histolysis are shown to be more consistent with the continuous model. Data from the present experiment on JHE are inconclusive, but results from a previous selection experiment also suggest that variation in JHE is consistent only with the continuous model.     

Cloning and characterization of BS-cadherin, a novel cadherin from the colonial urochordate Botryllus schlosseri

The genomic DNA for a novel member of the cadherin family (BS-cadherin) was cloned and characterized from the colonial marine invertebrate, Botryllus schlosseri. Using a differential display of mRNA by means of PCR, a small cDNA fragment of 380 nucleotides was found to be specifically expressed in a colony undergoing allogeneic rejection processes, as compared with naïve parts of the same genotype. This cDNA fragment was used as a probe to screen a genomic library of Botryllus schlosseri. A genomic fragment containing an ORF of 2718 nucleotides, with no introns, was isolated. The encoded protein exhibits a typical structure of cadherins; an extracellular domain with conserved repeated sequences (cadherin signatures), a single transmembrane domain and a conserved cytoplasmic tail region. The BS-cadherin amino-acid sequence shows 32–35% identity to mature classical cadherins type I, e.g., N-, P- and E-cadherin as well as mature classical cadherins type II, e.g., human cadherin-6, -8 and OB-cadherin. This cadherin represents a new cadherin gene family, evolutionarily distant to all other known classical cadherins.     

激光微束在两种鱼受精卵上打孔技术研究

在埃及胡子鲶和苏氏芒鲶两种鱼受精卵上,用脉冲ＹＡＧ激光微束打孔技术,成功地导入了外源指示剂和用激光微束打过孔的受精卵孵化出了仔鱼,为今后激光微束打孔植入外源基因和针类转基因研究做了一些有意义的探索工作。     

Coevolution of traits determining migratory tendency: correlated response of a critical enzyme,juvenile hormone esterase,to selection on wing morphology

Migratory tendency in insects is a complex trait, composed of a suite of correlated behavioural, physiological, morphological and life history traits. We investigate the genetic and physiological basis of the coevolution of this suite of traits using laboratory lines of the wing dimorphic cricket, Gryllus firmus, selected for increasing and decreasing incidence of macroptery. Selection on wing morphology has produced strong direct responses in proportion macropterous as well as correlated (indirect) responses in wing muscle histolysis, flight propensity and fecundity. We investigate the hypothesis that these responses have been mediated by changes in the metabolism of juvenile hormone (JH) during the final nymphal stadium (the critical period for wing morph determination). Previous studies of Gryllus sp. have established that JH titre in this period is determined primarily by the activity of the degradative enzyme, juvenile hormone esterase (JHE). Assays of JHE activity in the final nymphal stadium of the replicated control and selected lines demonstrate highly significant differences in both mean activity and the probability of macroptery for a given level of activity (i.e., the threshold activity required to induce wing formation). These correlated responses in JH metabolism support the general hypothesis that the correlations among traits determining migratory tendency result at least in part from the common influence of JH during the final nymphal stadium. We discuss these results in the context of the quantitative genetic model for the evolution of polygenic, dichotomous traits (the threshold model), and present four general predictions concerning the coevolution of traits associated with ecological (i.e., trophic, life history, behavioural) dimorphisms.