Aerial ultra-low-volume application of naled: impact on nontarget imperiled butterfly larvae (Cyclargus thomasi bethunebakeri) and efficacy against adult mosquitoes (Aedes taeniorhynchus)

We assessed the exposure and acute toxicity of naled, applied aerially as an ultra-low-volume spray for mosquito control, on late instar larvae of the Miami blue (Cyclargus thomasi bethunebakeri) (Comstock and Huntington 1943) (Lepidoptera: Lycaenidae), an imperiled South Florida butterfly. We concurrently evaluated the control efficacy against caged adult female salt-marsh mosquitoes (Aedes taeniorhynchus) (Wiedemann 1821) (Diptera: Culicidae). This 3-yr study was conducted in north Key Largo (Monroe County, FL) beginning in 2006. The field trials incorporated 15 sampling stations: nine in the target spray zone, three in the spray drift zone at varying distances from the target zone, and three in the control zone not subjected to naled spray drift. A total of six field spray trials were completed, three at an altitude of 30.5 m (100 feet), and three at 45.7 m (150 feet). For all trials, the ultra-low-volume application of Trumpet EC insecticide (78% naled) at a rate of 54.8 ml/ha (0.75 fl. oz/acre) was effective in killing caged adult mosquitoes in the target zone. Butterfly larvae survival was significantly reduced in the spray zone compared with drift and control zones. Analysis of insecticide residue data revealed that the mortality of the late instar butterfly larvae was a result of exposure to excess residues of naled. Additional research is needed to determine mitigation strategies that can limit exposure of sensitive butterflies to naled while maintaining mosquito control efficacy.     

Benefits for plants in ant-plant protective mutualisms: a meta-analysis

Costs and benefits for partners in mutualistic interactions can vary greatly, but surprisingly little is known about the factors that drive this variation across systems. We conducted a meta-analysis of ant-plant protective mutualisms to quantify the effects of ant defenders on plant reproductive output, to evaluate if reproductive effects were predicted from reductions in herbivory and to identify characteristics of the plants, ants and environment that explained variation in ant protection. We also compared our approach with two other recent meta-analyses on ant-plant mutualisms, emphasizing differences in our methodology (using a weighted linear mixed effects model) and our focus on plant reproduction rather than herbivore damage. Based on 59 ant and plant species pairs, ant presence increased plant reproductive output by 49% and reduced herbivory by 62%. The effects on herbivory and reproduction within systems were positively correlated, but the slope of this relationship (0.75) indicated that tolerance to foliar herbivory may be a common plant response to absence of ant guards. Furthermore, the relationship between foliar damage and reproduction varied substantially among systems, suggesting that herbivore damage is not a reliable surrogate for fitness consequences of ant protection. Studies that experimentally excluded ants reported a smaller effect of ant protection on plant reproduction than studies that relied upon natural variation in ant presence, suggesting that study methods can affect results in these systems. Of the ecological variables included in our analysis, only plant life history (i.e., annual or perennial) explained variation in the protective benefit of mutualistic ants: presence of ants benefitted reproduction of perennials significantly more than that of annuals. These results contrast with other quantitative reviews of these relationships that did not include plant life history as an explanatory factor and raise several questions to guide future research on ant-plant protection mutualisms.     

Studies on the mechanism of aromatase and other cytochrome P450 mediated deformylation reactions

Aromatase is a microsomal cytochrome P450 that converts androgens to estrogens by three sequential oxidations. The isolation of the 19-hydroxy and 19-oxo androgens suggests that the first two oxidations occur at the C₁₉ carbon. However, the mechanism of the third oxidation, which results in C₁₀---C₁₉ bond cleavage, has not been determined. Two proposed mechanisms which remain viable involve either initial 1β-hydrogen atom abstraction or addition of the ferric peroxy anion from aromatase to the C₁₉ aldehyde. Semiempirical molecular orbital calculations (AM1) were used to study potential reaction mechanisms initiated by initial 1β-hydrogen atom abstraction. Initially, the energetics of carbon---carbon bond cleavage of the keto and enol forms of C1-radicals were studied and were found to be energetically similar. A mechanism was proposed in which the 19-oxo intermediate is subject to initial nucleophilic attack by the protein. The geometry of the A-ring in the androgens is between that for the 1-radicals and estrogen, suggesting that some transition state stabilization for the homolytic cleavage reaction can occur.

More recently, studies on liver microsomal cytochrome P450 mediated deformylation of xenobiotic aldehydes supports mechanisms involving an alkyl peroxy intermediate formed by addition of the ferric peroxy anion from aromatase to the C₁₉ aldehyde. Although this intermediate could proceed through several different concerted or non-concerted pathways, one non-concerted pathway involves the heterolytic cleavage of the dioxygen bond resulting in an active oxygenating species (iron-oxene) and a diol. The diol could then undergo hydrogen atom abstraction followed by homolytic carbon---carbon bond cleavage as in the mechanisms modeled previously. When this cleavage was modeled for seven aldehydes, a good correlation with reported experimental aldehyde turnover numbers was obtained. However, when dialkoxy derivatives of the aldehydes are subject to microsomal metabolism, the rates of carbon---carbon cleavage products do not approach the rates of deformylation of the aldehyde analog.     

Plasmodium falciparum: continuous cultivation in a semiautomated apparatus.

A semi-automated apparatus for the continuous cultivation of the malarial parasite, Plasmodium falciparum, was developed. It changes the culture medium and redistributes ths infected erythrocytes at preselected intervals. Parasitemias between 2 and 16% can be maintained by adding fresh erythrocytes every 2 or 3 days. This apparatus produces approximately 10 ml of packed erythrocytes per week with parasitemias between 12 and 16%     

Plasmodium falciparum merozoites: isolation by density gradient centrifugation using Percoll and antigenic analysis

Merozoites of Plasmodium falciparum were isolated and immunocytochemically analyzed. Mature parasites from knobby (K+) and knobless (K-) strains were incubated for 4 to 5 hr in RPMI 1640 with 10% serum and 10% RBC extract. About 12 to 14% of the merozoites released were recovered by density gradient centrifugation using Percoll. From 1 to 3 X 10(9) merozoites were obtained per collection. The merozoite preparations were contaminated with 10% residual bodies, about 0.1% infected and uninfected erythrocytes, about 0.1% RBC-free trophozoites and schizonts, and numerous small (less than 0.5 microns) membrane vesicles. Merozoites from the K+ and K- strains were morphologically and, by an indirect, ferritin-labeled antibody assay using serum from immune Aotus, antigenically indistinguishable. Although the residual body coats reacted with the immune Aotus serum, the membrane vesicles, some of which were seen to be blebbing from merozoites, did not react with this serum or a serum against erythrocytes. This paper describes a procedure that can be used to obtain large numbers of merozoites with little contamination by host erythrocytes.