| 1. |
- Lindgren, Johan, et al.
(författare)
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Fossil insect eyes shed light on trilobite optics and the arthropod pigment screen
- 2019
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 573:7772, s. 122-125
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Tidskriftsartikel (refereegranskat)abstract
- Fossilized eyes permit inferences of the visual capacity of extinct arthropods1–3. However, structural and/or chemical modifications as a result of taphonomic and diagenetic processes can alter the original features, thereby necessitating comparisons with modern species. Here we report the detailed molecular composition and microanatomy of the eyes of 54-million-year-old crane-flies, which together provide a proxy for the interpretation of optical systems in some other ancient arthropods. These well-preserved visual organs comprise calcified corneal lenses that are separated by intervening spaces containing eumelanin pigment. We also show that eumelanin is present in the facet walls of living crane-flies, in which it forms the outermost ommatidial pigment shield in compound eyes incorporating a chitinous cornea. To our knowledge, this is the first record of melanic screening pigments in arthropods, and reveals a fossilization mode in insect eyes that involves a decay-resistant biochrome coupled with early diagenetic mineralization of the ommatidial lenses. The demonstrable secondary calcification of lens cuticle that was initially chitinous has implications for the proposed calcitic corneas of trilobites, which we posit are artefacts of preservation rather than a product of in vivo biomineralization4–7. Although trilobite eyes might have been partly mineralized for mechanical strength, a (more likely) organic composition would have enhanced function via gradient-index optics and increased control of lens shape.
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| 2. |
- Bowden, Stephen, et al.
(författare)
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The thermal alteration by pyrolysis of the organic component of small projectiles of mudrock during capture at hypervelocity
- 2008
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370. ; 82, s. 312-314
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Tidskriftsartikel (refereegranskat)abstract
- In a series of experiments the pyrolytic effects of the heating induced during the hypervelocity impact(HVI) of small projectiles of high TOC mudrock were observed. Impacts at these high speeds (km s-1)release sufficient energy to vaporise metal projectiles, and the temperatures created greatly exceed thepyrolysis temperatures typically employed during laboratory studies of the thermal alteration ofsedimentary organic matter. Despite this the organic geochemical analyses of projectiles of OrcadianLaminite impacted into targets of sand and water at hypervelocities provides evidence that the structuralbackbone of biomarkers has remained intact and that only a comparatively low degree of thermalalteration (pre-oil window) has occurred. While further studies are necessary, it appears that the organiccomponent of a projectile captured at hypervelocity will be a slightly thermally altered sample of itsprecursor.
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| 3. |
- Dredge, Ian, et al.
(författare)
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Elevated flux of cosmic spherules (micrometeorites) in Ordovician rocks of the Durness Group, NW Scotland
- 2010
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Ingår i: Scottish Journal of Geology. - : Geological Society of London. - 0036-9276 .- 2041-4951. ; 46, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- Limestone samples from the Cambro-Ordovician Durness Group were crushed, acid-digested and searched for evidence of micrometeorites. Eleven melted micrometeorites were extracted from the magnetic fraction of samples from the Balnakeil and Croisaphuill formations near the top of the group. Other formations in the Durness Group did not yield micrometeorites. Only melted spherules with a distinctive dendroidal crystalline structure (I-type cosmic spherules) were accepted as definite micrometeorites. They represent a flux of micrometeorites one to two orders of magnitude greater than at present. The micrometeorite-bearing formations are of Arenig age, coincident with the onset of an enhanced flux of extraterrestrial material identified by the occurrence of fossil meteorites in Sweden.
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| 4. |
- Fujiya, Wataru, et al.
(författare)
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Migration of D-type asteroids from the outer Solar System inferred from carbonate in meteorites
- 2019
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 3:10, s. 910-915
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Tidskriftsartikel (refereegranskat)abstract
- Recent dynamical models of Solar System evolution and isotope studies of rock-forming elements in meteorites have suggested that volatile-rich asteroids formed in the outer Solar System beyond Jupiter’s orbit, despite being currently located in the main asteroid belt. The ambient temperature under which asteroids formed is a crucial diagnostic to pinpoint the original location of asteroids and is potentially determined by the abundance of volatiles they contain. In particular, abundances and 13C/12C ratios of carbonates in meteorites record the abundances of carbon-bearing volatile species in their parent asteroids. However, the sources of carbon for these carbonates remain poorly understood. Here we show that the Tagish Lake meteorite contains abundant carbonates with consistently high 13C/12C ratios. The high abundance of 13C-rich carbonates in Tagish Lake excludes organic matter as their main carbon source. Therefore, the Tagish Lake parent body, presumably a D-type asteroid10, must have accreted a large amount of 13C-rich CO2 ice. The estimated 13C/12C and CO2/H2O ratios of ice in Tagish Lake are similar to those of cometary ice. Thus, we infer that at least some D-type asteroids formed in the cold outer Solar System and were subsequently transported into the inner Solar System owing to an orbital instability of the giant planets.
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| 5. |
- Gyllemark, Paula, et al.
(författare)
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Are other tick-borne infections overlooked in patients investigated for Lyme neuroborreliosis? : A large retrospective study from South-eastern Sweden
- 2021
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Ingår i: Ticks and Tick-borne Diseases. - : Elsevier GMBH. - 1877-959X .- 1877-9603. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- In Europe, the hard tick Ixodes ricinus is considered the most important vector of human zoonotic diseases. Human pathogenic agents spread by I. ricinus in Sweden include Borrelia burgdorferi sensu lato (s.l.), Anaplasma phagocytophilum, Rickettsia helvetica, the recently described Neoehrlichia mikurensis, Borrelia miyamotoi, tick-borne encephalitis virus (TBEV), and Babesia spp. (Babesia microti, Babesia venatorum and Babesia divergens). Since these pathogens share the same vector, co-infections with more than one tick-borne pathogen may occur and thus complicate the diagnosis and clinical management of the patient due to possibly altered symptomatology. Borrelia burgdorferi s.l., TBEV and B. miyamotoi are well-known to cause infections of the central nervous system (CNS), whereas the abilities of other tick-borne pathogens to invade the CNS are largely unknown. The aim of this study was to investigate the presence and clinical impact of tick-borne pathogens other than B. burgdorferi s.l. in the cerebrospinal fluid (CSF) and serum samples of patients who were under investigation for Lyme neuroborreliosis (LNB) in a tick-endemic region of South-eastern Sweden. CSF and serum samples from 600 patients, recruited from the Regions of center dot Ostergo center dot tland County, Jo center dot nko center dot ping County and Kalmar County in South-eastern Sweden and investigated for LNB during the period of 2009-2013, were retrospectively collected for analysis. The samples were analysed by real-time PCR for the presence of nucleic acid from B. burgdorferi s.l., B. miyamotoi, A. phagocytophilum, Rickettsia spp., N. mikurensis, TBEV and Babesia spp. Serological analyses were conducted in CSF and serum samples for all patients regarding B. burgdorferi s.l., and for the patients with CSF mononuclear pleocytosis, analyses of antibodies to B. miyamotoi, A. phagocytophilum, spotted fever group (SFG) rickettsiae, TBEV and B. microti in serum were performed. The medical charts of all the patients with CSF mononuclear pleocytosis and patients with positive PCR findings were reviewed. Of the 600 patients, 55 (9%) presented with CSF mononuclear pleocytosis, 13 (2%) of whom had Borrelia-specific antibodies in the CSF. One patient was PCRpositive for N. mikurensis, and another one was PCR-positive for Borrelia spp. in serum. No pathogens were detected by PCR in the CSF samples. Four patients had serum antibodies to B. miyamotoi, four patients to A. phagocytophilum, five patients to SFG rickettsiae, and six patients to TBEV. One patient, with antibodies to SFG
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| 6. |
- Henningsson, Anna, et al.
(författare)
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Low risk of seroconversion or clinical disease in humans after a bite by an Anaplasma phagocytophilum-infected tick
- 2015
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Ingår i: Ticks and Tick-borne Diseases. - : Elsevier. - 1877-959X .- 1877-9603. ; 6:6, s. 787-792
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Tidskriftsartikel (refereegranskat)abstract
- The risk of contracting human granulocytic anaplasmosis (HGA) after a tick bite is mainly unknown. In this study we investigated the clinical and serological response in 30 humans bitten by ticks positive for Anaplasma phagocytophilum (Group A), 30 humans bitten by Borrelia burgdorferi sensu lato (s.l.)-positive ticks (Group B), and 30 humans bitten by ticks negative for both A. phagocytophilum and B. burgdorferi s.l. (Group C). Ticks, blood samples and questionnaires were collected from tick-bitten humans at 34 primary healthcare centres in Sweden and in the Åland Islands, Finland, at the time of the tick bite and after three months. A total of 2553 ticks detached from humans in 2007-2009 were analyzed by polymerase chain reaction, and 31 (1.2%) were positive for A. phagocytophilum, 556 (21.8%) were positive for B. burgdorferi s.l., and eight (0.3%) were co-infected by A. phagocytophilum and B. burgdorferi s.l. The overall prevalence of Anaplasma IgG antibodies in the included participants (n=90) was 17%, and there was no significant difference between the groups A-C. Only one of the participants (in Group C) showed a four-fold increase of IgG antibodies against A. phagocytophilum at the three-month follow-up, but reported no symptoms. The frequency of reported symptoms did not differ between groups A-C, and was unrelated to the findings of A. phagocytophilum and B. burgdorferi s.l. in the detached ticks. We conclude that the risk for HGA or asymptomatic seroconversion after a tick bite in Sweden or in the Åland Islands is low, even if the tick is infected by A. phagocytophilum.
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| 7. |
- Lindgren, Paula, et al.
(författare)
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A demonstration of an affinity between pyrite and organic matter in a hydrothermal setting
- 2011
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Ingår i: Geochemical Transactions. - : Springer Science and Business Media LLC. - 1467-4866. ; 12, s. 3-
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Tidskriftsartikel (refereegranskat)abstract
- One of the key-principles of the iron-sulphur world theory is to bring organic molecules close enough to interact with each other, using the surface of pyrite as a substrate in a hydrothermal setting. The present paper explores the relationship of pyrite and organic matter in a hydrothermal setting from the geological record; in hydrothermal calcite veins from Carboniferous limestones in central Ireland. Here, the organic matter is accumulated as coatings around, and through, pyrite grains. Most of the pyrite grains are euhedral-subhedral crystals, ranging in size from ca 0.1-0.5 mm in diameter, and they are scattered throughout the matrix of the vein calcite. The organic matter was deposited from a hydrothermal fluid at a temperature of at least 200 degrees C, and gives a Raman signature of disordered carbon. This study points to an example from a hydrothermal setting in the geological record, demonstrating that pyrite can have a high potential for the concentration and accumulation of organic materials.
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| 8. |
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| 9. |
- Lindgren, Paula, et al.
(författare)
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Concentration of organic matter in hydrothermal deposits
- 2008
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Organic matter with various origins is commonly associated with hydrothermal activity. Examples from the terrestrial record include hydrothermally produced petroleum (Simoneit 1988), the possible formation of abiotic organic molecules (Holm 1992), and present-day biological activity around hydrothermal vents and hot springs (Corliss et al. 1979; Reysenbach and Cady 2001). If the conditions for preservation of the organic matter are favourable, hydrothermal deposits could be suitable sites for the detection of extraterrestrial organic matter, for example on Mars (e.g. Simoneit et al. 1998).The study of hydrothermal deposits in the terrestrial record allows us to gain more knowledge of the distribution of organic matter in various fossil hydrothermal settings. We have investigated fossil hydrothermal deposits on the Isle of Skye in Scotland, where the heat from igneous intrusions (Paleogene dolerite sills) in wet carbon-rich shale (Jurassic) has caused localized hydrothermal activity with the mobilization of organic-rich fluids. Here, the organic matter is accumulated in hydrothermal deposits: It occurs as vesicular hydrocarbon, located in hydrothermal veins together with calcite, chlorite and quartz, and as a cm-dm thick sheet sandwiched between the shale and the intrusive body. Organic matter also occurs in hydrothermally precipitated calcite veins that cross-cuts the igneous intrusion, and in vesicles of the igneous rock.This is one example from the terrestrial record showing that where organic matter is available, it can be mobilised and concentrated as a result of hydrothermal activity. The same process of carbon concentration could have taken place in ancient martian hydrothermal systems, induced by igneous activity or bolide impacts.
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| 10. |
- Lindgren, Paula, et al.
(författare)
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Organic geochemistry of the Haughton Impact Structure
- 2008
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Konferensbidrag (populärvet., debatt m.m.)abstract
- The Haughton Impact Structure (HIS) formed 39 Ma ago. The target rocks include Lower Palaeozoic aged limestone that contain small quantities of solvent extractable organic matter. The target bedrock, hydrothermal deposits and limestone clasts within impact melt breccias all yield fossil organic matter that has been thermally matured to varying degrees. But unusually for a terrestrial impact crater, molecular biomarkers survive. While many other impact structures on Earth (e.g. Gardnos) possess lithologies with associated organic carbon, thermal maturation prior or subsequent to the impact has destroyed any biomarkers that were present (note that this is not necessarily due to the impact itself). In other instances the biomarkers present are found in hydrocarbon accumulations and have migrated through the structure (e.g. Siljan). The HIS is unique in not experiencing subsequent regional metamorphism, furthermore the sedimentary organic matter is mostly present within the target rocks as inclusions of organic matter and not a free continuous petroleum phase (it has not migrated).The extraction and analysis of biomarkers from impactites from the HIS radically alters how an organic geochemist, looking to detect ancient molecular evidence of life, views the surface of a planetary body. For craters of a certain diameter (23 km), impact cratering, far from being an agent that obliterates the biomarker fossil record, can be shown to be a geological process more akin to tectonic activity: it has the potential to exhume geological formations that would otherwise be buried – albeit at the cost of a relatively minor increase in thermal maturity.
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