| 195281. |
- Tesson, Sylvie V.M., et al.
(författare)
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Description of Limnomonas gen. nov., L. gaiensis sp. nov. and L. spitsbergensis sp. nov. (Chlamydomonadales, Chlorophyta)
- 2022
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Ingår i: Diversity. - : MDPI AG. - 1424-2818. ; 14:6
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Tidskriftsartikel (refereegranskat)abstract
- Two novel Chlamydomonas-like species, belonging to the Moewusii clade, have been de-scribed. The first species inhabits eutrophic and neutral to basic pH waters in Sweden and England. It is easily recognizable under a light microscope due to its morphology (a small green prolate spheroidal shape with a large and truncated papilla at its anterior end, two equal flagella, a single lateral eyespot, a basal nucleus, and a well-defined pyrenoid) and to its peculiar whole-body pen-dulum movement while resting on surfaces or attached to floating particles. The species occurs as free-living individuals and is able to gather temporarily into groups of individual cells. No particular binding structures or palmelloid cells were observed in cultures. The second species, previously assigned to Chlamydomonas cf. proboscigera, was collected from persistent snow in Svalbard, Norway. Its morphology is revised herein. Using SSU rDNA sequence analyses, these two species formed a well-supported clade. Moreover, ITS-2 secondary structure analyses confirmed sexual incompatibility between these biological species. Considering these results, a new genus Limnomonas and its type species L. gaiensis and L. spitsbergensis are proposed.
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| 195282. |
- Tesson, Sylvie V.M., et al.
(författare)
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Dispersal in a changing world: opportunities, insights and challenges
- 2013
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Ingår i: Movement Ecology. - : Springer Science and Business Media LLC. - 2051-3933. ; :1-10
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- It has been long recognised that dispersal is an important life-history trait that plays a key role in the demography and evolution of populations and species. This then suggests that dispersal play a central role in the response of populations and species to ever-increasing global change, including climate change, habitat loss and fragmentation, and biological invasions. During a symposium held at Lund University (Sweden), the causes and consequences of dispersal were discussed, and here we provide an overview of the talks. As the discussions often gravitated towards the role and our understanding of dispersal in a changing world and given the urgent challenges posed by it, we place this overview in the context of global change. We draw and discuss four conclusions: (i) methodological advances provide opportunities for improved future studies, (ii) dispersal distances can be much greater than previously thought (examples in plants and vertebrates), but also much more restricted (examples in micro-organisms), (iii) dispersal is more dynamic than we often care to admit (e.g. due to individual variation, effects of parasites, variation in life history, developmental and evolutionary responses, community impacts), (iv) using results of dispersal research for detailed prediction of outcomes under global change is currently mostly out of reach – nevertheless, that should not stop us from showing the many negative consequences of global change, and how dispersal is often a limiting factor in adapting to this.
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| 195283. |
- Tesson, Sylvie V.M., et al.
(författare)
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Ice nucleation activity and aeolian dispersal success in airborne and aquatic microalgae
- 2018
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 9:NOV
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Tidskriftsartikel (refereegranskat)abstract
- Microalgae are common members of the atmospheric microbial assemblages. Diverse airborne microorganisms are known to produce ice nucleation active (INA) compounds, which catalyze cloud and rain formation, and thus alter cloud properties and their own deposition patterns. While the role of INA bacteria and fungi in atmospheric processes receives considerable attention, the numerical abundance and the capacity for ice nucleation in atmospheric microalgae are understudied. We isolated 81 strains of airborne microalgae from snow samples and determined their taxonomy by sequencing their ITS markers, 18S rRNA genes or 23S rRNA genes. We studied ice nucleation activity of airborne isolates, using droplet freezing assays, and their ability to withstand freezing. For comparison, we investigated 32 strains of microalgae from a culture collection, which were isolated from polar and temperate aqueous habitats. We show that ∼17% of airborne isolates, which belonged to taxa Trebouxiphyceae, Chlorophyceae and Stramenopiles, were INA. A large fraction of INA strains (over 40%) had ice nucleation activity at temperatures ≥-6°C. We found that 50% of aquatic microalgae were INA, but the majority were active at temperatures <-12°C. Most INA compounds produced by microalgae were proteinaceous and associated with the cells. While there were no deleterious effects of freezing on the viability of airborne microalgae, some of the aquatic strains were killed by freezing. In addition, the effect of desiccation was investigated for the aquatic strains and was found to constitute a limiting factor for their atmospheric dispersal. In conclusion, airborne microalgae possess adaptations to atmospheric dispersal, in contrast to microalgae isolated from aquatic habitats. We found that widespread taxa of both airborne and aquatic microalgae were INA at warm, sub-zero temperatures (>-15°C) and may thus participate in cloud and precipitation formation.
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| 195284. |
- Tesson, Sylvie V M, et al.
(författare)
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Integrating microorganism and macroorganism dispersal: modes, techniques and challenges with particular focus on co-dispersal
- 2015
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Ingår i: Ecoscience. - : Informa UK Limited. - 1195-6860. ; 22:2-4, s. 109-124
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Tidskriftsartikel (refereegranskat)abstract
- Whatever their size and the ecosystem they live in, all organisms may disperse at some stage of their life cycle. Dispersal dynamics are to a varying extent dependent on organismal size, life history, ecological niche, survival capacities and phylogeny. Moves towards a synthesis in dispersal ecology have focused primarily on vertebrates and higher plants, yet recent studies suggest that the dispersal of microorganisms and macroorganisms has much more in common than previously assumed. The dispersal of one organism enables co-dispersal for many others, smaller in size. There is an increasing need for a more integrated approach to study dispersal within the context of organismal interactions and their environments. Such an approach is facilitated by recent developments of powerful indirect techniques that enable tracking of microorganisms and macroorganisms over multiple spatial and temporal scales. Likewise, dispersal modelling and theoretical models of the consequences of dispersal can inspire empirical studies across the entire size spectrum. Simultaneously studying the relationships between dispersal of microorganisms and macroorganisms, and accounting for dispersal through time and space, will allow us to better understand the functioning and dynamics of communities and ecosystems, and to make better predictions of future dispersal patterns, changes in biodiversity and connectivity.
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| 195285. |
- Tesson, Sylvie V.M., et al.
(författare)
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Mendelian Inheritance Pattern and High Mutation Rates of Microsatellite Alleles in the Diatom Pseudo-nitzschia multistriata.
- 2012
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Ingår i: Protist. - : Elsevier BV. - 1434-4610.
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Tidskriftsartikel (refereegranskat)abstract
- The diatom Pseudo-nitzschia multistriata exhibits a diplontic life cycle composed of an extensive phase of vegetative cell division and a brief phase of sexual reproduction. To explore genotypic stability, we genotyped seven polymorphic microsatellite loci in 26 monoclonal strains over 3-16 months in a culture maintenance regime. Moreover, to assess inheritance patterns of the microsatellite alleles, we genotyped 246 F1 strains resulting from four mating experiments between parental strains of know genotype. Results generally conformed expectations according to Mendelian inheritance patterns, but deviations were detected indicating mutations during sexual reproduction. A total of forty-two mutations were detected in the clonal cultures over time. Microsatellites with more core-repeats accumulated mutations faster. The mutation rate varied significantly across loci and strains. A binomial mass function and a computer simulation showed that the mutation rate was significantly higher during the first months of culture (μ≈3×10(-3) per locus per cell division) and decreased to μ≈1×10(-3) in the strains kept for 16 months. Our results suggest that genetic mutations acquired in both the vegetative phase and sexual reproduction add to the allelic diversity of microsatellites, and hence to the genotypic variation present in a natural population.
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| 195286. |
- Tesson, Sylvie V.M., et al.
(författare)
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Microsatellite primers in the planktonic diatom Pseudo-nitzschia multistriata (Bacillariophyceae)
- 2011
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Ingår i: American Journal of Botany. - : Wiley. - 0002-9122. ; 98:2, s. 5-33
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Tidskriftsartikel (refereegranskat)abstract
- Premise of the study: Seven microsatellite loci were characterized for the toxic diatom Pseudo-nitzschia multistriata Takano (Takano) to investigate intraspecific variability and estimate population genetic structure over blooms, seasons, and sexual and vegetative reproduction. Methods and Results: Selected microsatellites consisted of di- and trinucleotide repeats in the core region, and showed four to twelve alleles per locus in strains of P. multistriata collected in the Gulf of Naples (Italy). Primer pairs were species-specific since they positively amplified against conspecific strains from Portugal and Spain but failed to generate PCR products from the diatoms Pseudo-nitzschia pseudodelicatissima (Hasle) Hasle and Leptocylindrus minimum Gran. Conclusions: The seven selected microsatellite markers will be useful in studying population dynamics of Pseudo-nitzschia multistriata in space and time.
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| 195287. |
- Tesson, Sylvie V.M., et al.
(författare)
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Population connectivity, dispersal, and swimming behavior in Daphnia
- 2021
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 11:6, s. 2873-2885
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Tidskriftsartikel (refereegranskat)abstract
- The water flea Daphnia has the capacity to respond rapidly to environmental stressors, to disperse over large geographical scales, and to preserve its genetic material by forming egg banks in the sediment. Spatial and temporal distributions of D. magna have been extensively studied over the last decades using behavioral or genetic tools, although the correlation between the two has rarely been the focus. In the present study, we therefore investigated the population genetic structure and behavioral response to a lethal threat, ultraviolet radiation (UVR), among individuals from two different water bodies. Our results show two genetic populations with moderate gene flow, highly correlated with geographical location and with inheritable traits through generations. However, despite the strong genetic differences between populations, we show homogeneous refuge demand between populations when exposed to the lethal threat solar UVR.
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| 195288. |
- Tesson, Sylvie V.M., et al.
(författare)
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The potential for dispersal of microalgal resting cysts by migratory birds
- 2018
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 54:4, s. 518-528
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Tidskriftsartikel (refereegranskat)abstract
- Most microalgal species are geographically widespread, but little is known about how they are dispersed. One potential mechanism for long-distance dispersal is through birds, which may transport cells internally (endozoochory) and deposit them during, or in-between, their migratory stopovers. We hypothesize that dinoflagellates, in particular resting stages, can tolerate bird digestion; that bird temperature, acidity, and retention time negatively affect dinoflagellate viability; and that recovered cysts can germinate after passage through the birds’ gut, contributing to species-specific dispersal of the dinoflagellates across scales. Tolerance of two dinoflagellate species (Peridiniopsis borgei, a warm-water species and Apocalathium malmogiense, a cold-water species) to Mallard gut passage was investigated using in vitro experiments simulating the gizzard and caeca conditions. The effect of in vitro digestion and retention time on cell integrity, cell viability, and germination capacity of the dinoflagellate species was examined targeting both their vegetative and resting stages. Resting stages (cysts) of both species were able to survive simulated bird gut passage, even if their survival rate and germination were negatively affected by exposure to acidic condition and bird internal temperature. Cysts of A. malmogiense were more sensitive than P. borgei to treatments and to the presence of digestive enzymes. Vegetative cells did not survive conditions of bird internal temperature and formed pellicle cysts when exposed to gizzard-like acid conditions. We show that dinoflagellate resting cysts serve as dispersal propagules through migratory birds. Assuming a retention time of viable cysts of 2–12 h to duck stomach conditions, cysts could be dispersed 150–800 km and beyond.
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| 195289. |
- Testa, A. C., et al.
(författare)
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Imaging in gynecological disease (1): ultrasound features of metastases in the ovaries differ depending on the origin of the primary tumor
- 2007
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Ingår i: Ultrasound in Obstetrics & Gynecology. - : Wiley. - 1469-0705 .- 0960-7692. ; 29:5, s. 505-511
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Tidskriftsartikel (refereegranskat)abstract
- Objective To describe the gray-scale and color Doppler ultrasound findings of metastatic tumors in the ovary according to the origin of the primary tumor. Methods Information was retrieved retrospectively from 67 patients who had undergone preoperative transvaginal gray-scale and color Doppler ultrasound examination and who were found subsequently to have metastatic tumors in their ovaries. In all women the ultrasound information had been collected prospectively using a standardized examination technique and predefined definitions of ultrasound characteristics. Stored ultrasound images were used only to describe retrospectively the external surface of the metastatic tumors. Information on presenting symptoms and on whether the patient had been treated for a malignancy in the past was retrieved retrospectively from patient records. Results Most (95%) ovarian metastases were solid, multilocular-solid or multilocular. Almost all (38/41, 93%) metastases that derived from the stomach, breast, lymphoma or uterus were solid, while most (16/22, 73%) metastases deriving from the colon, rectum, appendix or biliary tract were multilocular or multilocular-solid (P < 0.0001). Metastases that derived from the colon, rectum, appendix or biliary tract were larger compared with those from the stomach, breast, lymphoma or uterus (median maximum diameter, 122 (range, 16-200) mm vs. 71 (range, 27-170) mm, P = 0.02). In addition, irregular external borders were more common (19/22 (86%) vs. 19/41 (46%), P = 0.002), as were papillary projections (6/22 (27%) vs. 2/41 (5%), P = 0.011). They also appeared to be less vascularized, with 64% (14/22) manifesting moderate-to-abundant vascularization at color Doppler examination in comparison to 88% (36/41) of the ovarian metastases from stomach, breast, lymphoma or uterus (P = 0.024). Conclusion Ovarian metastases derived from lymphoma or from tumors in the stomach, breast and uterus are solid in almost all cases, whereas those derived from the colon, rectum or biliary tract manifest more heterogeneous morphological patterns, most being multicystic with irregular borders. Copyright (c) 2007 ISUOG. Published by John Wiley & Sons, Ltd.
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| 195290. |
- Testa, A. C., et al.
(författare)
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Intravenous contrast ultrasound examination using contrast-tuned imaging (CnTI (TM)) and the contrast medium SonoVue (R) for discrimination between benign and malignant adnexal masses with solid components
- 2009
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Ingår i: Ultrasound in Obstetrics & Gynecology. - : Wiley. - 1469-0705 .- 0960-7692. ; 34:6, s. 699-710
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Tidskriftsartikel (refereegranskat)abstract
- Objective To determine whether intravenous contrast ultrasound examination is superior to gray-scale or power Doppler ultrasound for discrimination between benign and malignant adnexal masses with complex ultrasound morphology. Methods In an international multicenter study, 134 patients with an ovarian mass with solid components or a multilocular cyst with more than 10 cyst locules, underwent a standardized transvaginal ultrasound examination followed by contrast examination using the contrast-tuned imaging technique and intravenous injection of the contrast medium SonoVue (R). Time intensity curves were constructed, and peak intensity, area under the intensity curve, time to peak, sharpness and half wash-out time were calculated. The sensitivity and specificity with regard to malignancy were calculated and receiver-operating characteristics (ROC) curves were drawn for gray-scale, power Doppler and contrast variables and for pattern recognition (subjective assignment of a certainly benign, probably benign, uncertain or malignant diagnosis, using gray-scale and power Doppler ultrasound findings). The gold standard was the histological diagnosis of the surgically removed tumors. Results After exclusions (surgical removal of the mass > 3 months after the ultrasound examination, technical problems), 72 adnexal masses with solid components were used in our statistical analyses. The values for peak contrast signal intensity and area under the contrast signal intensity curve in malignant tumors were significantly higher than those in borderline tumors and benign tumors, while those for the benign and borderline tumors were similar. The area under the ROC curve of the best contrast variable with regard to diagnosing borderline or invasive malignancy (0.84) was larger than that of the best gray-scale (0.75) and power Doppler ultrasound variable (0.79) but smaller than that of pattern recognition (0.93). Conclusion Findings on ultrasound contrast examination differed between benign and malignant tumors but there was a substantial overlap in contrast findings between benign and borderline tumors. It appears that ultrasound contrast examination is not superior to conventional ultrasound techniques, which also have difficulty in distinguishing between benign and borderline tumors, but can easily differentiate invasive malignancies from other tumors. Copyright (C) 2009 ISUOG. Published by John Wiley & Sons, Ltd.
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