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Thaddeus Metz 《Developing world bioethics》2018,18(3):233-240
Many countries in Africa, and more generally those in the Global South with tropical areas, are plagued by illnesses that the wealthier parts of the world (mainly ‘the West’) neither suffer from nor put systematic effort into preventing, treating or curing. What does an ethic with a recognizably African pedigree entail for the ways various agents ought to respond to such neglected diseases? As many readers will know, a characteristically African ethic prescribes weighty duties to aid on the part of those in a position to do so, and it therefore entails that there should have been much more contribution from the Western, ‘developed’ world. However, what else does it prescribe, say, on the part of sub‐Saharan governments and the African Union, and are they in fact doing it? I particularly seek to answer these questions here, by using the 2013‐16 Ebola crisis in West Africa to illustrate what should have happened but what by and large did not. 相似文献
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Luis A. Buatois M. Gabriela Mángano 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2013,46(3):281-292
Ichnodiversity has been used as a proxy for environmental stress and stability in facies interpretations and to reconstruct evolutionary radiations and colonization histories in evolutionary palaeoecology. The three components of global diversity are exported from ecology and adapted for ichnology. Alpha ichnodiversity is used for palaeoenvironmental characterization, being assessed for individual facies. Beta ichnodiversity is commonly overlooked, although it may provide information about degree of similarity between ichnofaunas formed along environmental gradients. Gamma ichnodiversity may provide clues to detect ichnofossil provincialism. The concept of disparity may also prove to be significant in ichnological studies. Whereas ichnodiversity refers to ichnotaxonomic richness, ichnodisparity provides a measure of the variability of morphological plans in biogenic structures. Changes in global ichnodiversity do not necessarily parallel changes in ichnodisparity. For example, while the Cambrian explosion involved a dramatic increase in both, the Ordovician radiation essentially reflects an increase only in the former. Ichnodiversity and ichnodisparity should be used with caution because they are both affected by taphonomic processes. High diversity of superficial to shallow‐tier trace fossils may result from enhanced preservation due a poorly developed mixed layer, rather than a true reflection of ecosystem performance, as shown by underexploited infaunal ecospace after biotic crises (e.g. end‐Permian mass extinction). 相似文献
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Concordance of bacterial communities of two tick species and blood of their shared rodent host
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Evelyn C. Rynkiewicz Chris Hemmerich Douglas B. Rusch Clay Fuqua Keith Clay 《Molecular ecology》2015,24(10):2566-2579
High‐throughput sequencing is revealing that most macro‐organisms house diverse microbial communities. Of particular interest are disease vectors whose microbiome could potentially affect pathogen transmission and vector competence. We investigated bacterial community composition and diversity of the ticks Dermacentor variabilis (n = 68) and Ixodes scapularis (n = 15) and blood of their shared rodent host, Peromyscus leucopus (n = 45) to quantify bacterial diversity and concordance. The 16S rRNA gene was amplified from genomic DNA from field‐collected tick and rodent blood samples, and 454 pyrosequencing was used to elucidate their bacterial communities. After quality control, over 300 000 sequences were obtained and classified into 118 operational taxonomic units (OTUs, clustered at 97% similarity). Analysis of rarefied communities revealed that the most abundant OTUs were tick species‐specific endosymbionts, Francisella and Rickettsia, and the commonly flea‐associated bacterium Bartonella in rodent blood. An Arsenophonus and additional Francisella endosymbiont were also present in D. variabilis samples. Rickettsia was found in both tick species but not in rodent blood, suggesting that it is not transmitted during feeding. Bartonella was present in larvae and nymphs of both tick species, even those scored as unengorged. Relatively, few OTUs (e.g. Bartonella, Lactobacillus) were found in all sample types. Overall, bacterial communities from each sample type were significantly different and highly structured, independent of their dominant OTUs. Our results point to complex microbial assemblages inhabiting ticks and host blood including infectious agents, tick‐specific endosymbionts and environmental bacteria that could potentially affect arthropod‐vectored disease dynamics. 相似文献
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Louis M. Weiss Melanie T. Cushion Elizabeth Didier Lihua Xiao Francine Marciano‐Cabral Anthony P. Sinai Olga Matos Enrique J. Calderon Edna S. Kaneshiro 《The Journal of eukaryotic microbiology》2013,60(3):298-308
The 12th International Workshops on Opportunistic Protists (IWOP‐12) was held in August 2012 in Tarrytown, New York. The objectives of the IWOP meetings are to: (1) serve as a forum for exchange of new information among active researchers concerning the basic biology, molecular genetics, immunology, biochemistry, pathogenesis, drug development, therapy, and epidemiology of these immunodeficiency‐associated pathogenic eukaryotic microorganisms that are seen in patients with AIDS and (2) foster the entry of new and young investigators into these underserved research areas. The IWOP meeting focuses on opportunistic protists, e.g. the free‐living amoebae, Pneumocystis, Cryptosporidium, Toxoplasma, the Microsporidia, and kinetoplastid flagellates. This conference represents the major conference that brings together research groups working on these opportunistic pathogens. Slow but steady progress is being achieved on understanding the biology of these pathogenic organisms, their involvement in disease causation in both immune‐deficient and immune‐competent hosts, and is providing critical insights into these emerging and reemerging pathogens. This IWOP meeting demonstrated the importance of newly developed genomic level information for many of these pathogens and how analysis of such large data sets is providing key insights into the basic biology of these organisms. A great concern is the loss of scientific expertise and diversity in the research community due to the ongoing decline in research funding. This loss of researchers is due to the small size of many of these research communities and a lack of appreciation by the larger scientific community concerning the state of art and challenges faced by researchers working on these organisms. 相似文献
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Nematodes associated with Ips cembrae (Coleoptera: Curculionidae): comparison of generations,sexes and sampling methods
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A study of nematodes associated with the large larch bark beetle Ips cembrae (Heer 1836) was carried out at three locations in the Czech Republic. The proportion of beetles infested by endoparasitic nematodes (representatives of genera Contortylenchus, Parasitylenchus, Cryptaphelenchus and Parasitorhabditis) ranged from 29.9 to 50.9%. Significant differences were determined in nematode infestation levels among locations, generations and sampling methods. No differences were found in infestation rates between males and females. The percentage of bark beetles with phoretic nematodes ranged from 18 to 42.9%. Phoretic nematodes directly found under elytra, on wings and between body segments of the bark beetles belong to the genus Micoletzkya. However, adults and juveniles of other two phoretic species Laimaphelenchus penardi and Bursaphelenchus sp. were found in the gallery frass of I. cembrae. Infestation by phoretic nematodes positively correlated with the presence of mites under elytra. 相似文献
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Alexander S. Mikheyev Carolyn S. McBride Ulrich G. Mueller Camille Parmesan Melanie R. Smee Constanti Stefanescu Brian Wee Michael C. Singer 《Molecular ecology》2013,22(18):4753-4766
Ecotypic variation among populations may become associated with widespread genomic differentiation, but theory predicts that this should happen only under particular conditions of gene flow, selection and population size. In closely related species, we might expect the strength of host‐associated genomic differentiation (HAD) to be correlated with the degree of phenotypic differentiation in host‐adaptive traits. Using microsatellite and Amplified Fragment Length Polymorphism (AFLP) markers, and controlling for isolation by distance between populations, we sought HAD in two congeneric species of butterflies with different degrees of host plant specialization. Prior work on Euphydryas editha had shown strong interpopulation differentiation in host‐adapted traits, resulting in incipient reproductive isolation among host‐associated ecotypes. We show here that Euphydryas aurinia had much weaker host‐associated phenotypic differentiation. Contrary to our expectations, we detected HAD in Euphydryas aurinia, but not in E. editha. Even within an E. aurinia population that fed on both hosts, we found weak but significant sympatric HAD that persisted in samples taken 9 years apart. The finding of significantly stronger HAD in the system with less phenotypic differentiation may seem paradoxical. Our findings can be explained by multiple factors, ranging from differences in dispersal or effective population size, to spatial variation in genomic or phenotypic traits and to structure induced by past histories of host‐adapted populations. Other infrequently measured factors, such as differences in recombination rates, may also play a role. Our result adds to recent work as a further caution against assumptions of simple relationships between genomic and adaptive phenotypic differentiation. 相似文献
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Kefyalew Alemayehu 《African Journal of Ecology》2013,51(2):280-287
Population viability analysis (PVA) has been applied to the management of many threatened populations. The objective of this study was, therefore, to estimate the PVA of Walia ibex at the Simen Mountains National Park, in the north‐central highlands of Ethiopia, with respect to population growth parameters, the probability of the population reaching a lower extinction threshold and the mean time to extinction. Direct census of the population was carried out in 2009. Secondary census data were also collected from park authorities and the literature reviews. The result revealed that the estimates of the infinitesimal mean, μ (0.04117) was greater than the infinitesimal variance, σ2 (0.0219). The probability that the population reaches the extinction threshold was very low (0.15%). The mean time required for the counts to decline from the existing population size to one individual animal was 160 years. But threatened species are adversely affected by changes in landscape. These changes can be brought by short‐ and long‐term human and climate change impacts, respectively. Therefore, with the absence of environmental and demographic stochasticity and, with the application of appropriate reproductions and habitat management, the population of Walia ibex will be viable and reaches its mean time of extinctions after 160 years. 相似文献
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Mai Mitoma Yumi Kajino Risa Hayashi Miyako Endo Shosei Kubota Akira Kanno 《The Plant journal : for cell and molecular biology》2019,99(3):439-451
Habenaria radiata (Orchidaceae) has two whorls of perianth, comprising three greenish sepals, two white petals and one lip (labellum). By contrast, the pseudopeloric (with a decreased degree of zygomorphy) mutant cultivar of H. radiata , ‘Hishou’, has changes in the identities of the dorsal sepal to a petaloid organ and the two ventral sepals to lip‐like organs. Here, we isolated four DEFICIENS ‐ like and two AGL 6 ‐like genes from H. radiata , and characterized their expression. Most of these genes revealed similar expression patterns in the wild type and in the ‘Hishou’ cultivar, except Hr DEF ‐C3. The Hr DEF ‐C3 gene was expressed in petals and lip in the wild type but was ectopically expressed in sepal, petals, lip, leaf, root and bulb in ‘Hishou’. Sequence analysis of the Hr DEF ‐C3 loci revealed that the ‘Hishou’ genome harbored two types of Hr DEF ‐C3 genes: one identical to wild‐type Hr DEF ‐C3 and the other carrying a retrotransposon insertion in its promoter. Genetic linkage analysis of the progeny derived from an intraspecific cross between ‘Hishou’ and the wild type demonstrated that the mutant pseudopeloric trait was dominantly inherited and was linked to the Hr DEF ‐C3 gene carrying the retrotransposon. These results indicate that the pseudopeloric phenotype is caused by retrotransposon insertion in the Hr DEF ‐C3 promoter, resulting in the ectopic expression of Hr DEF ‐C3 . As the expression of Hr AGL 6‐C2 was limited to lateral sepals and lip, the overlapping expression of Hr DEF ‐C3 and Hr AGL 6‐C2 is likely to be responsible for the sepal to lip‐like identity in the lateral sepals of the ‘Hishou’ cultivar. 相似文献
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Dynein heavy chains are motor proteins that comprise a large gene family found across eukaryotes. We have investigated this gene family in four ciliate species: Ichthyophthirius, Oxytricha, Paramecium, and Tetrahymena. Ciliates appear to encode more dynein heavy chain genes than most eukaryotes. Phylogenetic comparisons demonstrated that the last common ancestor of the ciliates that were examined expressed at least 14 types of dynein heavy chains with most of the expansion coming from the single‐headed inner arm dyneins. Each of the dyneins most likely performed different functions within the cell. 相似文献
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Rocío Fernández S. Nandini S.S.S. Sarma María Elena Castellanos‐Paez 《Invertebrate Biology》2014,133(4):371-380
Simocephalus vetulus is a large (2.0–4.0 mm at maturity) cladoceran often found in the littoral region of lakes and ponds, and capable of moderate growth rates even on poor‐quality cyanobacterial diets. It frequently co‐occurs with fishes and similar sized ostracods such as Heterocypris incongruens, but little is known of its response to fish kairomones or its interactions with potential competitors. We studied the demographic responses of S. vetulus fed the green alga Scenedesmus acutus, Microcystis cf. aeruginosa strain A, Microcystis cf. aeruginosa strain B, or Limnothrix sp. Experiments were conducted separately and together in the presence of Heterocypris incongruens and cichlid fish (Oreochromis) kairomones. A diet of Limnothrix sp. resulted in the lowest population growth rate (0.21±0.023 d?1), while on diets of S. acutus or Microcystis, population growth was higher (0.30±0.009 d?1). The presence of ostracods resulted in significantly higher growth rates of S. vetulus fed Limnothrix (0.33±0.01 d?1), but not Microcystis or S. acutus. Regardless of the diet, the presence of fish kairomones resulted in significantly higher growth rates as compared with controls, particularly when ostracods were also present. Coexistence with ostracods may be beneficial to S. vetulus, particularly when food quality is poor. 相似文献
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Fredric V. Vencl Kristina Ottens Marjorie M. Dixon Sarah Candler Ximena E. Bernal Catalina Estrada Rachel A. Page 《Biotropica》2016,48(5):645-655
Although famous for photic courtship displays, fireflies (Coleoptera: Lampyridae) are also notable for emitting strong odors when molested. The identity of volatile emissions and their possible role, along with photic signals, as aposematic warnings of unpalatability have been little explored, especially in tropical species. Pursuant to the observation that the widespread Neotropical fireflies, Photuris trivittata and Bicellonycha amoena, emit pungent odors, glows, and flashes when handled, we investigated their cuticular and headspace chemistry. Gas chromatography–mass spectrometry analyses revealed that both fireflies have species‐specific cuticular hydrocarbon profiles. Photuris trivittata headspace was dominated by 2‐methoxy‐3‐(1‐methylpropyl) pyrazine (hereafter, pyrazine), on the order of 1.59 ng/individual and a suite of sesquiterpenes, while B. amoena emitted 3‐methoxy‐2‐butenoic acid methyl ester and a few ketones. This is the first report of such compounds in fireflies. We investigated the role of pyrazine in P. trivittata's interactions with potential predators: sympatric ants, toads, and bats. Solvent‐washed P. trivittata painted with pyrazine incurred lower ant predation than did their solvent‐washed counterparts. Pyrazine significantly repelled ants at baits in concentrations as low as 9.8 × 10?4 ng/μl. The toad, Rhinella marina, readily accepted intact fireflies, pyrazine‐coated and uncoated mealworms. Both Myotis nigricans and Molossus molossus bats rejected fireflies, but accepted both pyrazine‐coated and uncoated mealworms. While pyrazine repels ants, its role as an aposematic signal warning other potential predators of firefly distastefulness requires further investigation. Our results underscore the idea that multiple enemies exert conflicting selection on firefly defenses. 相似文献
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Stephen K. Donovan 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2021,54(1):1-3
‘Train crash crinoids’ represent an unusual mode of preservation of crinoid columns, superficially resembling to the carriages of a crashed train. They were exhumed from the White Peak (Mississippian limestones) of the Peak District in the Treak Cliff area of Castleton, Derbyshire, north‐central England, and were presented by Broadhurst & Simpson as part of a varied suite of observations supporting the recognition of an ancient apron reef (= fore‐reef slope). A re‐examination of these specimens shows that they were not live crinoids at or near the reef crest, but were recently dead specimens, recumbent on the sediment surface. Something triggered their movement into deeper water, and some travelled downslope parallel to the direction of movement and broke into a ‘train crash pattern’ when the lower end impacted on an immovable object. 相似文献
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Muhammad Ashfaq Muhammad Asif Zahid Iqbal Anjum Yusuf Zafar 《Molecular ecology resources》2013,13(4):573-582
Although two plastid regions have been adopted as the standard markers for plant DNA barcoding, their limited resolution has provoked the consideration of other gene regions, especially in taxonomically diverse genera. The genus Gossypium (cotton) includes eight diploid genome groups (A–G, and K) and five allotetraploid species which are difficult to discriminate morphologically. In this study, we tested the effectiveness of three widely used markers (matK, rbcL, and ITS2) in the discrimination of 20 diploid and five tetraploid species of cotton. Sequences were analysed locus‐wise and in combinations to determine the most effective strategy for species identification. Sequence recovery was high, ranging from 92% to 100% with mean pairwise interspecific distance highest for ITS2 (3.68%) and lowest for rbcL (0.43%). At a 0.5% threshold, the combination of matK+ITS2 produced the greatest number of species clusters. Based on ‘best match’ analysis, the combination of matK+ITS2 was best, while based on ‘all species barcodes’ analysis, ITS2 gave the highest percentage of correct species identifications (98.93%). The combination of sequences for all three markers produced the best resolved tree. The disparity index test based on matK+rbcL+ITS2 was significant (P < 0.05) for a higher number of species pairs than the individual gene sequences. Although all three barcodes separated the species with respect to their genome type, no single combination of barcodes could differentiate all the Gossypium species, and tetraploid species were particularly difficult. 相似文献
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Zelalem Mersha Shouan Zhang Yuqing Fu Xiaodan Mo Richard N. Raid Bernhard Hau 《Journal of Phytopathology》2013,161(3):154-164
Downy mildew, caused by the oomycete pathogen Peronospora belbahrii, is a devastating foliar disease of basil in the United States and worldwide. Currently there are very few chemistries or organic choices registered to control this disease. In this study, two systemic acquired resistance (SAR) inducers, acibenzolar‐S‐methyl (ASM) and β‐aminobutyric acid (BABA), were evaluated for their in vitro effects on the pathogen, for their potential to control basil downy mildew in greenhouses, and for changes in peroxidase activity in basil plants treated with these two SAR inducers. No significant inhibition of sporangial germination was detected in water agar amended with ASM at concentrations lower than 100 mg/l or with BABA at concentrations lower than 500 mg/l. Efficacy of ASM and BABA in greenhouses varied depending on the rate, method and timing of application. The area under the disease progress curve (AUDPC) of disease severity was significantly reduced compared to the non‐treated control when ASM was sprayed (in all experiments) or drenched (in one out of two experiments) pre‐, or pre‐ + post‐inoculation at rates of 25–400 mg/l. Three weekly post‐inoculation sprays of ASM at the rate of 50 mg/l reduced AUDPC by 93.0 and 47.2% when started 3 and 7 days after inoculation (DAI), respectively. The AUDPC of disease severity was also significantly reduced when BABA was sprayed pre‐ + post‐inoculation at rates of 125–500 mg/l. According to the prediction using a log‐logistic function, 50% maximum disease protection was achieved at a concentration of 27.5 mg/l of ASM. Basil plants treated with these two SAR inducers and challenged with the pathogen showed significantly higher peroxidase activity than the non‐treated control at 8 DAI. Temporally, the highest activity of peroxidase was detected at 8 DAI, decreased at 15 DAI and waned further at 23 DAI. 相似文献
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Effects of iron deficiency on the growth and photosynthesis of three bloom‐forming cyanobacterial species isolated from Lake Taihu
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Cyanobacterial blooms are found in many freshwater ecosystems around the world, but the effect of environmental factors on their growth and the proportion of species still require more investigation. In this study, the physiological responses of bloom‐forming cyanobacteria M icrocystis aeruginosa FACHB912, M icrocystis flos‐aquae FACHB1028 and P seudanabaena sp. FACHB1282 to iron deficiency were investigated. Their specific growth rates were found to decrease as the available iron concentration decreased. At low available iron concentrations of 1 × 10?7 M (pFe 21.3) and 5 × 10?8 M (pFe 21.6), M . aeruginosa had the lowest specific growth rate among three studied species. The cell sizes of M . flos‐aquae and Pseudanabaena sp. were significantly smaller under the lowest iron concentration. The chlorophyll a content of the three species decreased at the lowest iron concentration. The maximal relative electron transport rate, photosynthetic efficiency, and light‐saturation parameter of M . aeruginosa were lower than the other two cyanobacteria at pFe 21.3. Therefore, M . aeruginosa was the least able to adapt to iron deficiency. Under iron deficiency, the functional absorption cross‐section of PSII and electron transport rate on the acceptor side of PSII decreased in M . aeruginosa, while the connectivity factor between individual photosynthetic units increased in M . flos‐aquae, and the electron transport rate on the acceptor side of PSII and between PSII and PSI decreased in P seudanabaena sp. The ability to store iron was highest in M . flos‐aquae, followed by P seudanabaena sp. and M . aeruginosa. Thus, these results provide necessary information for detecting the role of iron in the succession of cyanobacterial species in Lake Taihu, the third largest freshwater lake in China, because all three species were isolated from this lake. 相似文献