1,721,006 research outputs found
May climate change allow the spread of the Asian tiger mosquito, vector of viruses, in central Europe?
Full text linkAedes albopictus, also known as the Asian tiger mosquito, is a native species of tropical and subtropical areas of Southeast Asia, recently spread also to Europe. Ae. albopictus represents a serious threat for human health because it is an important vector of many viruses. The geographical distribution of the mosquito’s populations is limited by cold climate. However, according to projections, due to the climate change the species could spread in many regions where it is now not established. The key factor that allowed Ae. albopictus to colonize new territories in higher latitudes may be the production of cold-tolerant diapausing eggs. The aim of this study is to determine the parameters for the production of diapausing eggs by Ae. albopictus and for the eggs hatching. According to our data, the diapausing eggs are induced by a 11 hours of light and 13 of dark photoperiod that, in central Italy, is reached during the middle of October. Thank to this mechanism, the mosquito can avoid the exposition to low temperature of the most susceptible stage of development, the first instar larva, that cannot survive under 10°C. The results are discussed in relation to the scenario of the global warming
Insights into Notonecta maculata biology and its consumptive and non‐consumptive effects on Aedes albopictus
No full textNotonecta species (Hemiptera: Notonectidae) are generalist true predators with a strong impact on the size, structure, and richness of the aquatic communities, particularly on mosquito populations. Juvenile and adult backswimmers not only prey on mosquito larvae (consumptive effect) but their presence can also deter the oviposition of gravid mosquito females (non-consumptive effect). In this study, we selected a Western Palearctic backswimmer, Notonecta maculata Fabricius, as a predator and deterrent of the highly invasive and health-threatening Asian tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae). In central Italy, N. maculata is univoltine and overwinters in the adult stage. Females lay eggs from February to the end of May, and the first new adults will emerge in late June; the complete nymphal development requires 44.5 +/- 3.1 days. The number of Ae. albopictus larvae preyed on by N. maculata during its growth increases while developing, going from 0.03 +/- 0.02 larvae per day for first instar nymphs to 21.38 +/- 2.90 for mature adults. Furthermore, the presence of a single N. maculata adult in a mosquito ovitrap is enough to discourage the Ae. albopictus oviposition for up to 5 days. Limiting mosquito populations and, consequently, the transmission of viruses and parasites should be our main goal. Therefore, the integrated management of Ae. albopictus by the use of insecticides and a predator (such as backswimmer juveniles and adults), even if only in specific situations, may be promising and feasible. A more in-depth knowledge of the biological cycle of N. maculata could help, consequently, to optimize its mass rearing
Multiple Functions of Malpighian Tubules in Insects: A Review
Full text linkThe Malpighian Tubules (MTs) are the main excretory organs in most insects. They play a key role in the production of primary urine and osmoregulation, selectively reabsorbing water, ions, and solutes. Besides these functions conserved in most insects, MTs can serve some specialized tasks at different stages of some species’ development. The specialized functions include the synthesis of mucopolysaccharides and proteins for the building of foam nests, mucofibrils for the construction of dwelling tubes, adhesive secretions to help the locomotion, and brochosomes for protection as well as the usage of inorganic salts to harden the puparia, eggs chorion, and pupal cells’ closing lids. MTs are also the organs responsible for the astonishing bioluminescence of some Diptera glowworms and can go through some drastic histological changes to produce a silk-like fiber utilized to spin cocoons. The specialized functions are associated with modifications of cells within the entire tubules, in specific segments, or, more rarely, modified secretory cells scattered along the MTs. In this review, we attempted to summarize the observations and experiments made over more than a century concerning the non-excretive functions of insects’ MTs, underlying the need for new investigations supported by the current, advanced technologies available to validate outdated theories and clarify some dubious aspects
Expression of homeobox genes during in vitro culture of Lactuca sativa
No full textLettuce, Lactuca sativa, is one of the main leafy vegetable crops, interesting as a source of phytonutrients. It is extensively studied for biotechnological applications based on in vitro regeneration. However, in lettuce, histological studies of adventitious morphogenesis during the regeneration process are lacking. Analogously, the genes involved in the initiation of adventitious shoots or embryos are unknown. Here, we used cotyledon explants of a cos lettuce (‘Romana’) to define the histological events of in-vitro morphogenesis at different times, and to investigate the nature of the regeneration pathway. Furthermore, we isolated three homeobox genes, LsWUSCHEL1-LIKE (LsWUS1L), LsWUS2L, and LsSHOOT MERISTEMLESS1-LIKE (LsSTM1L), to evaluate their transcription activity during the ontogenesis of the adventitious structures. De novo morphogenesis quickly proceeded through embryogenic and organogenic pathways, with some developmental abnormalities. The expression of LsWUS1L gradually increased during the in vitro culture of cotyledon explants. Remarkably, we detected high expression of both LsWUS2L and LsSTM1L genes after four days of culture, when the very early stages of morphogenesis were only noticeable through histological analysis. These findings suggest a key role of these genes in the rapid recruitment of the founder cells of adventitious structures
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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