Entomological observations on dengue vector mosquitoes following a suspected outbreak of dengue in certain parts of Nagaland with a note on their susceptibility to insecticides

Three species of Aedes viz., Aedes albopictus, Aedes aegypti and Aedes annandalei were detected from different breeding sources in and around human habitats during entomological study conducted following an outbreak suspected to be of dengue (which occurred during, 1994) in parts of Medziphema PHC area of Nagaland in two different points of time ie., in the year, 1994 and, 2000. The potential dengue vector, Aedes albopictus showed high preponderance by breeding in all types of containers searched with high Breteau Index (BI) value of 85.0 and 72.72 recorded in, 1994 and, 2000 respectively whereas the BI value for other potential vector, Aedes aegypti was recorded low (4.9) in the year, 1994 with a substantial increase (31.81) in, 2000. The change in ecosystem along with the process of urbanization has facilitated the growth of these dengue vector mosquitoes in the area of investigation. Adults of both Aedes aegypti and Aedes albopictus were found to be susceptible to DDT, dieldrin and malathion in insecticide bioassay carried out using WHO test kit.     

Relative susceptibility of some common mosquito vector larvae to synthetic insecticidal compounds in north-western Rajasthan

Relative susceptibility of three important mosquito vector larvae viz., Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus, prevalent in the arid region was determined against four organophosphates (malathion, fenitrothion, fenthion, temephos) and three synthetic pyrethroid (alphamethrin, deltamethrin and fanvalerate) compounds. Studies were carried out on late 3rd or early 4th instar larvae of these species using standard WHO technique. Based on concentration mortality data LC50 and LC90 values along with their fiducial limits, regression equation, chi-square (chi2)/heterogeneity of the response have been determined by log probit regression analysis. LC50 values as observed for the above seven insecticides were 0.8097, 0.0398. 0.0432, 0.0035, 0.0025, 0.0092, 0.1006; 1.2370, 0.0531, 0.0655, 0.0076, 0.00004, 0.00004, 0.0046 and 1.4980, 0.0719, 0.0817, 0.0056, 0.00021, 0.00073, 0.0112 mg/l for the above three mosquito species respectively Among the four organophosphates tested temephos was the most effective followed by fenitrothion, fenthion and malathion. In general, Anopheles was found more susceptible as compared to the other two culicines to the above four compounds. The results also showed that larvae of Ae. aegypti were most susceptible followed by Cx. quinquefasciatus and An. stephensi to all the three pyrethroids tested. Among the three compounds tested alphamethrin was found to be the most toxic followed by deltamethrin while fanvalerate was the least toxic. The study would be of great importance while planning use of these insecticides for the control of different vector species in this area.     

Comparative larvicidal potential of different plant parts of Withania somnifera against vector mosquitoes in the semi-arid region of Rajasthan

Larvicidal potential of the extracts from different parts viz. green and red fruits, seeds, fruit without seeds, leaves and roots of Withania somnifera in different solvents was evaluated against larvae of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus, the important disease vectors prevalent in the semi-arid region. Experiments were carried out on late 3rd or early 4th instar larvae of these mosquitoes using standard WHO technique. 24 and 48 hr LC50 values along with their 95% confidence limits, regression equation, chi-square (chi2)/heterogeneity of the response have been determined by log probit regression analysis. The 24 hr LC50 values as observed for whole green fruits in water, methanol and petroleum ether were 350.9, 372.4, 576.9; 115.0, 197.1, 554.6; 154.9, 312.0, 1085.0 while corresponding values for red fruits were 473.5, 406.4,445.2; 94.7, 94.5, 1013.0; 241.8, 535.0, 893.3 mg l(-1) for An. stephensi, Ae. aegypti and Cx. quinquefasciatus respectively showing that methanol extracts were more effective against anophelines as compared to culicines when whole fruits were taken. The 24 hr LC50 values as observed for seeds in acetone, methanol and petroleum ether were 188.1, 777.5, 822.5; 245.5, 769.0, 1169.0; 140.3, 822.9, 778.4 and for fruit without seeds were 80.2, 97.6, 146.6; 88.4, 404.4, 1030.0; 30.0, 44.5, 54.2 mg l(-1) for the above mosquito species respectively showing that extract of fruit without seeds were most effective in petroleum ether followed by acetone and methanol extracts. However, experiments conducted with methanol extracts of leaves and roots of this plant species did not show any appreciable larvicidal activity and a 20-40% mortality was observed up to 500 mg l(-1) of the extracts. Overall larvae of anophelines were found more susceptible as compared to culicines to all the extracts tested. Petroleum ether extract of fruit without seeds was found most effective against all the mosquito species showing that active ingredient might be present in this part of the plant species. The study would be of great importance while planning vector control strategy based on alternative plant derived insecticides.     

Transport,fate, and toxicity of selected public health insecticides in waterways

Application of public health insecticides for mosquito control has increased dramatically with the recent outbreaks in the continental United States of dengue, chikungunya, and Zika. Mosquito control is often controversial because of the potential impacts on health and the environment due to the chemicals used. The emphasis in this review is to examine the transport, fate, and potential effects of the active ingredients in selected public health insecticides used for mosquito control. Due to the many potential entry points for insecticides, especially in urban areas where use is less monitored and application may be in greater amounts per unit area, this review suggests that a potential focus might be on the prevalence and quantification of the cumulative concentrations of these insecticides in natural systems. Often concentrations resulting from a single application are unlikely to cause mortality, but multiple applications may result in concentrations of environmental concern. Minimizing entrance to waterways and public water supply sources can be achieved by applying insecticides during prime meteorological conditions where drift and volatilization are minimized, using vegetated buffer zones in agricultural areas to prevent runoff, and avoiding application to impervious surfaces in urban areas.     

Organochlorine insecticide residues in Egyptian mothers’ milk

Two hundred ninety‐two mother's milk samples were collected during 1994 from ten Egyptian governorates representing rural, metropolitan, and newly reclaimed desert areas. The samples were analyzed for 14 organochlorine insecticides and metabolites using electron capture gas chromatography and confirmed by gas chromatography/mass spectrometry (GC/MS). The overall samples average showed that the most abundant organochlorine insecticide residues were p,p'‐DDE, α‐endosulfan, β‐HCH and, p,p’‐DDT. Residues in the range of not detectable to less than 14μg/l whole milk were recorded for α‐HCH, heptachlor, heptachlor epoxide, aldrin, dieldrin, endrin endrin aldehyde and p,p'‐DDD. The percentage of samples exceeding the acceptable daily intake for children (ADIs) set by the FAO/WHO ranged from 19% to 44% in all governorates included in the study except the governorate of Minia in which only 2.6% of the samples exceeded the ADI values. The insecticides exceeding ADI values are mostly heptachlor and heptaclor epoxide (ADI = 3.12 μg/1 whole milk).     

Association of body mass with price of bushmeat in Nigeria and Cameroon

Spatially extensive patterns of bushmeat extraction (and the processes underlying these patterns) have not been explored. We used data from a large sample (n= 87) of bushmeat trading points in urban and rural localities in Nigeria and Cameroon to explore extraction patterns at a regional level. In 7,594 sample days, we observed 61,267 transactions involving whole carcasses. Rural and urban trading points differed in species for sale and in meat condition (fresh or smoked). Carcass price was principally associated with body mass, with little evidence that taxonomic group (primate, rodent, ungulate, or mammalian carnivore) affected price. Moreover, meat condition was not consistently associated with price. However, some individual species were more expensive throughout the region than would be expected for their size. Prices were weakly positively correlated with human settlement size and were highest in urban areas. Supply did not increase proportionally as human settlement size increased, such that per capita supply was significantly lower in urban centers than in rural areas. Policy options, including banning hunting of more vulnerable species (those that have low reproductive rates), may help to conserve some species consumed as bushmeat because carcass prices indicate that faster breeding, and therefore the more sustainable species, may be substituted and readily accepted by consumers.     

Associations between soil lead concentrations and populations by race/ethnicity and income-to-poverty ratio in urban and rural areas

Lead (Pb) is a well-studied environmental contaminant that has many negative health effects, especially for children. Both racial/ethnic and income disparities have been documented with respect to exposure to Pb in soils. The objectives of this study were to assess whether soil Pb concentrations in rural and urban areas of South Carolina USA, previously identified as having clusters of intellectual disabilities (ID) in children, were positively associated with populations of minority and low-income individuals and children (≤6 years of age). Surface soils from two rural and two urban areas with identified clusters of ID were analyzed for Pb and concentrations were spatially interpolated using inverse distance weighted analysis. Population race/ethnicity and income-to-poverty ratio (ITPR) from United States Census 2000 block group data were aerially interpolated by block group within each area. Urban areas had significantly higher concentrations of Pb than rural areas. Significant positive associations between black, non-Hispanic Latino, individuals and children ≤6 years of age and mean estimated Pb concentrations were observed in both urban (r = 0.38, p = 0.0007) and rural (r = 0.53, p = 0.04) areas. Significant positive associations also were observed between individuals and children with an ITPR < 1.00 and Pb concentrations, though primarily in urban areas. Racial/ethnic minorities and low ITPR individuals, including children, may be at elevated risk for exposure to Pb in soils.     

Impacts of rural to urban migration,urbanization, and generational change on consumption of wild animals in the Amazon

For the first time in history, more people live in urban areas than in rural areas. This trend is likely to continue, driven largely by rural-to-urban migration. We investigated how rural-to-urban migration, urbanization, and generational change affect the consumption of wild animals. We used chelonian (tortoises and freshwater turtles), one of the most hunted taxa in the Amazon, as a model. We surveyed 1356 households and 2776 school children across 10 urban areas of the Brazilian Amazon (6 small towns, 3 large towns, and Manaus, the largest city in the Amazon Basin) with a randomized response technique and anonymous questionnaires. Urban demand for wild meat (i.e., meat from wild animals) was alarmingly high. Approximately 1.7 million turtles and tortoises were consumed in urban areas of Amazonas during 2018. Consumption rates declined as size of the urban area increased and were greater for adults than children. Furthermore, the longer rural-to-urban migrants lived in urban areas, the lower their consumption rates. These results suggest that wild meat consumption is a rural-related tradition that decreases as urbanization increases and over time after people move to urban areas. However, it is unclear whether the observed decline will be fast enough to conserve hunted species, or whether children's consumption rate will remain the same as they become adults. Thus, conservation actions in urban areas are still needed. Current conservation efforts in the Amazon do not address urban demand for wildlife and may be insufficient to ensure the survival of traded species in the face of urbanization and human population growth. Our results suggest that conservation interventions must target the urban demand for wildlife, especially by focusing on young people and recent rural to urban migrants. Article impact statement: Amazon urbanite consumption of wildlife is high but decreases with urbanization, over time for rural to urban migrants, and between generations. Impactos de la Migración del Campo a la Ciudad, la Urbanización y del Cambio Generacional sobre el Consumo de Animales Silvestres en el Amazonas     

河西走廊中部荒漠植被的生态学研究

根据对河西走廊中部荒漠植被的调查，对荒漠植被进行了分类及生态学描述，重点讨论了荒漠植被对改善河西走廊中部农村生态环境的作用，提出了保护和利用荒漠植被的措施及改善生态环境的途径。     

杭州市城乡乔木物种的多样性

沿杭州市区至临安农村取1 km宽75 km长样带调查乔木物种多样性。调查结果表明市区本土树种保存较好,树种数量达到20余种,农村物种丰富度极低,树种数量仅有10种左右。从物种丰富度指数可以看出市区物种最为丰富,丰富度指数最高达4.343,郊区物种丰富度指数最低,为1.303,农村物种丰富度指数较郊区有所上升,但仍显著低...     

Consumer resource matching in urbanizing landscapes: are synanthropic species over-matching?

Population responses of synanthropic species to urbanization may be explained by the resource-matching rule, which postulates that individuals should distribute themselves according to resource availability. According to the resource-matching rule, urban habitats will contain greater densities if they provide better resources than rural habitats. However, because resource availability is density dependent, individuals in urban areas would ultimately achieve fitness levels comparable to, but no better than, individuals in less urban areas. Some ecologists suggest that synanthropic birds may not conform to the resource-matching rule and may instead overmatch (i.e., overexploit) in urban habitats, ultimately leading to lower fitness despite greater resource levels. Using the Northern Cardinal (Cardinalis cardinalis) as a focal species, we evaluated if Cardinal populations in urban and rural habitats were consistent with predictions of consumer resource matching. During 2003-2006 we documented population density, adult body condition, apparent survival, and annual reproductive productivity of Cardinals in riparian forest stands within urban (n = 8 stands) and rural (n = 6 stands) landscapes in Ohio, USA. Density of Cardinals in urban forests was four times that found in more rural forests. Mark-resight data from 147 males and 125 females over four years indicated that apparent survival rates were similar between urban and rural landscapes (phi = 0.64, SE = 0.039 for males and phi = 0.57, SE = 0.04 for females). Similarly, body condition indices of 168 males, 142 females, and 118 nestlings did not differ significantly between landscapes. Annual reproductive productivity (mean number of fledglings per pair over breeding season) of 294 pairs was comparable for urban (2.4 +/- 0.18 [mean +/- SE] and rural (2.1 +/- 0.18) young birds. Thus, contrary to recent suggestions, we find that high densities of certain synanthropic species in urban landscapes are consistent with expectations of consumer resource matching.     

Complex responses within a desert bee guild (Hymenoptera: Apiformes) to urban habitat fragmentation.

Urbanization within the Tucson Basin of Arizona during the past 50+ years has fragmented the original desert scrub into patches of different sizes and ages. These remnant patches and the surrounding desert are dominated by Larrea tridentata (creosote bush), a long-lived shrub whose flowers are visited by > 120 native bee species across its range. Twenty-one of these bee species restrict their pollen foraging to L. tridentata. To evaluate the response of this bee fauna to fragmentation, we compared species incidence and abundance patterns for the bee guild visiting L. tridentata at 59 habitat fragments of known size (0.002-5 ha) and age (up to 70 years), and in adjacent desert. The 62 bee species caught during this study responded to fragmentation heterogeneously and not in direct relation to their abundance or incidence in undisturbed desert. Few species found outside the city were entirely absent from urban fragments. Species of ground-nesting L. tridentata specialists were underrepresented in smaller fragments and less abundant in the smaller and older fragments. In contrast, cavity-nesting bees (including one L. tridentata specialist) were overrepresented in the habitat fragments, probably due to enhanced nesting opportunities available in the urban matrix. Small-bodied bee species were no more likely than larger bodied species to be absent from the smaller fragments. The introduced European honey bee, Apis mellifera, was a minor faunal element at > 90% of the fragments and exerted little if any influence on the response of native bee species to fragmentation. Overall, bee response to urban habitat fragmentation was best predicted by ecological traits associated with nesting and dietary breadth. Had species been treated as individual units in the analyses, or pooled together into one analysis, these response patterns may not have been apparent. Pollination interactions with this floral host are probably not adversely affected in this system because of its longevity and ability to attract diverse pollinators but will demand careful further study to understand.     

天津市“城-郊-乡”样带土壤种子库特征分析

为了解天津市不同地理位置土壤种子库物种组成和群落结构的变化,沿天津市设置＂城区—城郊—远郊＂的生态样带,在6个典型样地选取20个样方进行土壤种子库的采样工作并进行萌发试验。结果表明：土壤种子库的密度、物种组成及群落结构差异性明显,除趋势对应分析后分异出典型的城市土壤种子库、城郊土壤种子库、远郊土壤种子库3种类型。从远郊到城区,土壤种子库的密度递增,相似性指数也递增,而物种丰富度却递减。相比远郊地区,城区、城郊区土壤种子库物种丰富度损失率分别为66.67%、45.23%。城区因城市化水平较高及频繁的人为干扰致使土壤种子库物种呈现匀质化特点,物种多为一年生的耐踩踏草本。城郊区的多样性指数、生态优势度指数、均匀度指数最低,但是种子库密度较大,物种丰富,萌发种子中木本植物可观,适合用于进行植被恢复的试验研究。     

Organochlorine pesticides in soils around Guanting Reservoir,China

Fifty-six representative samples of topsoil were collected around Guanting Reservoir, which is an important water source for Beijing. Concentrations of the insecticides HCH, DDT, and their metabolites were quantified by use of gas chromatography (GC) with electron capture detection (ECD). Organochlorine pesticides (OCPs) are still present in surface soils in the Guanting area. DDT accounts for about 93% of the total OCP content. Concentrations of α/γ, β/γ, and DDT/DDE are the result not only of historical use, but also of more recent depositions. Statistical analyses, including principal component analysis (PCA) and cluster analysis (CA), revealed associations between concentrations of OCPs and major soil characteristics. Geographical information system (GIS) technology was used to develop maps of the distributions of OCP concentrations. The areas of greatest contamination were primarily in the central part of the study area and were correlated with greater population density, heavier traffic, and more industrial activity.     

不同生态区土壤溶磷微生物的分布特征及影响因子

研究了盐渍区、重金属污染区和磷矿区土壤中溶磷微生物的数量、组成及与部分土壤化学因子的关系。结果表明,溶磷微生物在不同生态区土壤中的分布各不相同,磷矿区土壤中溶磷微生物数量和种群丰度普遍高于重金属污染区和盐渍区,但优势种属间数量差异不明显。重金属污染土壤中溶磷细菌比例较高,但种群单一,主要以巨大芽孢杆菌(Bacillus megaterium)为优势种,重金属污染区溶磷细菌比例与土壤重金属综合污染指数呈显著正相关(P<0.01),溶磷细菌丰度与有机质含量呈显著正相关(P<0.05)。盐渍土中溶磷细菌比例小,优势种群为巨大芽孢杆菌、假单胞杆菌属(Pseudomonassp.)和黄单胞杆菌属(Flavobacteriumsp.),其数量和种群丰度分别与有机质和有效磷含量呈显著相关关系(P<0.05)。     

Polychlorinated biphenyls and Organochlorine insecticides residues in fish and shellfish from lake Biwa

Results of surveys on Polychlorinated biphenyls (PCB) and organochlorine insecticides (HCH and DDT) in fish and shellfish from Lake Biwa were summarized from 1987 to 1996. In 1975, fish and shellfish in Lake Biwa were highly contaminated with PCB, HCH and DDT but recently in 1992–1996 the concentrations of these chemicals were very low and nearly constant. In the composition of HCH isomers, β‐HCH was dominant in all kinds of fish and shellfish. In the composition of DDT and DDT metabolites, pp'‐DDE was similarly dominant in all kinds of fish and shellfish. Further, the data in Lake Biwa were compared with those in Lake Michigan and Lake Baikal.     

Spider, bee, and bird communities in cities are shaped by environmental control and high stochasticity

Spatially organized distribution patterns of species and communities are shaped by both autogenic processes (neutral mechanism theory) and exogenous processes (niche theory). In the latter, environmental variables that are themselves spatially organized induce spatial structure in the response variables. The relative importance of these processes has not yet been investigated in urban habitats. We compared the variance explained by purely spatial, spatially structured environmental, and purely environmental components for the community composition of spiders (Araneae), bees (Apidae), and birds (Aves) at 96 locations in three Swiss cities. Environmental variables (topography, climate, land cover, urban green management) were measured on four different radii around sampling points (< 10 m, 50 m, 250 m, 1000 m), while Moran's eigenvector maps (MEMs) acted as spatial variables. All three taxonomic groups showed weak spatial structure. Spider communities reacted to very fine-scaled environmental changes of lawn and meadow management and climate. Bird community composition was determined by woody plants as well as solar radiation at all radii, the scale of the influence varying among species. Bee communities were weakly explained by isolated variables only. Our results suggest that the anthropogenic structuring of urban areas has disrupted the spatial organization of environmental variables and inhibited the development of biotic spatial processes. The near absence of spatial structure may therefore be a feature typical of urban species assemblages, resulting in urban community composition mainly influenced by local environmental variables. Urban environments represent a close-knit mosaic of habitats that are regularly disturbed. Species communities in urban areas are far from equilibrium. Our analysis also suggests that urban communities need to be considered as being in constant change to adapt to disturbances and changes imposed by human activities.     

Songbird abundance and parasitism differ between urban and rural shrublands.

Many studies have examined differences in avian community composition between urban and rural habitats, but few, if any, have looked at nesting success of urban shrubland birds in a replicated fashion while controlling for habitat. We tested factors affecting nest survival, parasitism by the Brown-headed Cowbird (Molothrus ater), and species abundance in shrubland habitat in rural and urban landscapes. We found no support for our hypothesis that nest survival was lower in urban landscapes, but strong support for the hypothesis that survival increased with nest height. We found strong support for our hypothesis that cowbird parasitism was greater in urban than rural landscapes; parasitism in urban sites was at least twice that of rural sites. We found strong support for an urban landscape effect on abundance for several species; Northern Cardinal (Cardinalis cardinalis) and Brown-headed Cowbirds were more abundant in urban landscapes, whereas Field Sparrow (Spizella pusilla) and Blue-winged Warbler (Vermivora pinus) were more abundant in rural sites. There was support for lower abundances of Blue-gray Gnatcatcher (Polioptila caerulea) and Indigo Bunting (Passerina cyanea) with increased housing density. For six other species, edge and trail density or vegetation parameters best explained abundance. Lower abundances and greater parasitism in habitat patches in urban landscapes are evidence that, for some species, these urban landscapes do not fulfill the same role as comparable habitats in rural landscapes. Regional bird conservation planning and local habitat management in urban landscapes may need to consider these effects in efforts to sustain bird populations at regional and local scales.     

Chemical contamination and sediment toxicity along the coast of Corsica

Trace metals (Cd, Pb, Cu, Cr, Ni, Co, Zn, Hg, As, Mn, Al, Fe, and Li) and organic compounds (PCBs, PAHs, lindanes, and DDT and its degradation products) were measured in coastal sediment samples from 27 sites in lagoons and along coastal areas of Corsica. An oyster embryo bioassay evaluated the toxicity of sediments from sites in three coastal lagoons (Urbino, Diane, and Biguglia) and the west coast of Cape Corsica. Despite contamination levels generally lower than those in other Mediterranean coastal areas, contamination is found in specific sites in Corsica and includes natural arsenic contamination on the east coast, insecticide pollution (persistent lindane and DDT) in many areas, both cadmium and lead contamination around Sagone, general contamination of both main harbours (Bastia and Ajaccio) and their surrounding areas, and asbestos mining residues in western Cape Corsica. Monitoring development of Crassostrea gigas embryos showed toxic effects at sites near a factory on Cape Corsica, with up to 100% mortality of larvae, and lower levels of toxicity at Sagone (44% mortality) and in the three coastal lagoons (up to 28% mortality). Results of this regional study show the need for further monitoring to understand the environmental issues facing the Corsican coast.     

Hierarchical Bayesian scaling of soil properties across urban, agricultural, and desert ecosystems.

Ecologists increasingly use plot-scale data to inform research and policy related to regional and global environmental change. For soil chemistry research, scaling from the plot to the region is especially difficult due to high spatial variability at all scales. We used a hierarchical Bayesian model of plot-scale soil nutrient pools to predict storage of soil organic carbon (oC), inorganic carbon (iC), total nitrogen (N), and available phosphorus (avP) in a 7962-km2 area including the Phoenix, Arizona, USA, metropolitan area and its desert and agricultural surroundings. The Bayesian approach was compared to a traditional approach that multiplied mean values for urban mesic residential, urban xeric residential, nonresidential urban, agricultural, and desert areas by the aerial coverage of each land-use type. Both approaches suggest that oC, N, and avP are correlated with each other and are higher (in g/m2) in mesic residential and agricultural areas than in deserts or xeric residential areas. In addition to traditional biophysical variables, cultural variables related to impervious surface cover, tree cover, and turfgrass cover were significant in regression models predicting the regional distribution of soil properties. We estimate that 1140 Gg of oC have accumulated in human-dominated soils of this region, but a significant portion of this new C has a very short mean residence time in mesic yards and agricultural soils. For N, we estimate that 130 Gg have accumulated in soils, which explains a significant portion of "missing N" observed in the regional N budget. Predictions for iC differed between the approaches because the Bayesian approach predicted iC as a function of elevation while the traditional approach employed only land use. We suggest that Bayesian scaling enables models that are flexible enough to accommodate the diverse factors controlling soil chemistry in desert, urban, and agricultural ecosystems and, thus, may represent an important tool for ecological scaling that spans land-use types. Urban planners and city managers attempting to reduce C emissions and N pollution should consider ways that landscape choices and impervious surface cover affect city-wide soil C, N, and P storage.