The chemistry of antipredator defense by secondary compounds in neotropical lepidoptera: facts, perspectives and caveats

Chemical defense against predation in butterflies and moths has been studied since nineteenth century. A classical example is that of the larvae of the monarch butterfly Danaus plexippus, which feed on leaves of Asclepias curassavica (Asclepiadaceae), sequestering cardenolides. The adults are protected against predation by birds. Several other substances may be involved in chemical defense, such as iridoid glycosides, cyanogenic glycosides, glucosinolates, pyrrolizidine and tropane alkaloids, aristolochic acids, glycosidase inhibitors and pyrazines. The acquisition of these substances by lepidopterans can be due to sequestration from larval or adult host plants or de novo biosynthesis. Many Lepidoptera are known to be unpalatable, including the butterflies Troidini (Papilionidae), Pierinae (Pieridae), Eurytelinae, Melitaeinae, Danainae, Ithomiinae, Heliconiinae and Acraeinae (Nymphalidae), and Arctiidae moths, but knowledge of the chemical substances responsible for property is often scarce. This review discusses mainly three topics: field and laboratory observations on rejection of butterflies and moths by predators, correlation between unpalatability and chemicals found in these insects, and bioassays that test the activity of these chemicals against predators. Perspectives and future directions are suggested for this subject.Defesas químicas em lepidópteros contra predadores têm sido observadas desde o século XIX. O caso clássico de proteção química contra predadores é o da borboleta monarca, Danaus plexippus, cuja larva seqüestra cardenolidas de sua planta hospedeira Asclepias curassavica e transfere-as para os adultos tornando-os impalatáveis para pássaros. Entretanto diversas outras substâncias podem estar envolvidas na proteção química de lepidópteros neotropicais (glicosídeos iridóides, glicosídeos cianogênicos, glicosinolatos, alcalóides pirrolizidínicos e tropânicos, ácidos aristolóquicos, inibidores de glicosidase, pirazinas). Esses compostos podem ser seqüestrados da planta hospedeira larval, obtidos de fontes vegetais visitadas por adultos ou biossintetizados de novo. Os lepidópteros conhecidos como impalatáveis para predadores vertebrados e/ou invertebrados são as borboletas Troidini (Papilionidae), Pierinae (Pieridae), Eurytelinae, Melitaeinae, Danainae, Ithomiinae, Heliconiinae e Acraeinae (Nymphalidae) e mariposas Arctiidae. Entretanto informações sobre as substâncias que são responsáveis pela impalatabilidade e como elas são adquiridas nem sempre são obtidas. Esse artigo de revisão aborda principalmente observações de campo e laboratório sobre a rejeição de borboletas e mariposas neotropicais por predadores, correlações entre impalatabilidade e substâncias químicas encontradas nos insetos e bioensaios que demonstrem a atividade dessas substâncias contra predadores. Perspectivas são sugeridas para esses tópicos.551561Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Generation and remote detection of THz sound using semiconductor superlattices

The authors introduce a novel approach to study the propagation of high frequency acoustic phonons in which the generation and detection involves two spatially separated superlattices $\sim 1 {\rm \mu m}$ apart. Propagating modes of frequencies up to $\sim 1 {\rm THz}$ escape from the superlattice where they are generated and reach the second superlattice where they are detected. The measured frequency spectrum reveals finite size effects, which can be accounted for by a continuum elastic model.Comment: Submitted to Applied Physics Letter

Results of the Rio de Janeiro magnetic observations 1781?1788

International audienceWe have compiled a relatively extensive catalogue of geomagnetic declination measurements performed by the Portuguese Bento Sanches Dorta in Rio de Janeiro (Brazil) between 1781 and 1788. All the information was retrieved from printed documents compiled in the first three volumes of the Memories of the Portuguese Royal Academy of Sciences. During this period Sanches Dorta performed roughly 20000 individual observations, however, only a fraction of this data is presently available. In this work, all available information about these measurements is analysed. The annual change (variability and trend) and the daily cycle of geomagnetic declination at monthly scale are discussed. Keywords. Geomagnetism and paleomagnetism, History of geophysics, Geomagnetic field declinatio

Explosive development of winter storm Xynthia over the subtropical North Atlantic Ocean

In winter of 2009–2010 south-western Europe was hit by several destructive windstorms. The most important was Xynthia (26–28 February 2010), which caused 64 reported casualties and was classified as the 2nd most expensive natural hazard event for 2010 in terms of economic losses. In this work we assess the synoptic evolution, dynamical characteristics and the main impacts of storm Xynthia, whose genesis, development and path were very uncommon. Wind speed gusts observed at more than 500 stations across Europe are evaluated as well as the wind gust field obtained with a regional climate model simulation for the entire North Atlantic and European area. Storm Xynthia was first identified on 25 February around 30° N, 50° W over the subtropical North Atlantic Ocean. Its genesis occurred on a region characterized by warm and moist air under the influence of a strong upper level wave embedded in the westerlies. Xynthia followed an unusual SW–NE path towards Iberia, France and central Europe. The role of moist air masses on the explosive development of Xynthia is analysed by considering the evaporative sources. A lagrangian model is used to identify the moisture sources, sinks and moisture transport associated with the cyclone during its development phase. The main supply of moisture is located over an elongated region of the subtropical North Atlantic Ocean with anomalously high SST, confirming that the explosive development of storm Xynthia had a significant contribution from the subtropics

Insect Mortality In Spathodea Campanulata Beauv. (bignoniaceae) Flowers.

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