| 1. |
- Karlsson, Maria, et al.
(författare)
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Continuous and stepwise oocyte production in Libellulidae (Anisoptera)
- 2010
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Ingår i: Odonatologica. - Utrecht, Netherlands : Societas Internationalis Odonatologica. - 0375-0183. ; 39:2, s. 107-119
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Tidskriftsartikel (refereegranskat)abstract
- Compared to other insect groups, libellulids have a rather high mean number of ovarioles. In addition, the mean ovariole diameter differs greatly between and within species. In general, 2 different types of ovariole arrangement exist: (1) all developing oocytes mature and equal in size; in some species without, and in others with, surrounding connective tissue and (2) oocytes displaying gradual maturation, with only the outermost ovarioles mature. These differences have ecological consequences: the first arrangement occurs in spp. that have stepwise egg production. These spp. will lay one or more clutches, after which an interclutch interval of ovariole regrowth follows. Spp. with the second arrangement have continuous egg production and are able to lay at least some eggs all the time, reducing the length of interclutch intervals. However, no direct connection between mate-guarding strategies and ovariole arrangements can be seen. Nevertheless, it is believed that the process of ovariole maturation differs between these groups. It is concluded that ovary morphology in libellulids may exhibit evolutionary fixed traits, although the whole picture still remains complex. The ovariole arrangement may have a crucial impact on the reproductive ecology of the species.
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| 2. |
- Koch, Kamilla, et al.
(författare)
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Farmland versus forest : comparing changes in Odonata species composition in western and eastern Sweden
- 2014
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Ingår i: Insect Conservation and Diversity. - Chichester, West Sussex : Wiley-Blackwell. - 1752-458X .- 1752-4598. ; 7:1, s. 22-31
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Tidskriftsartikel (refereegranskat)abstract
- 1. Despite the loss of natural ecosystems in the developed world during the past millennia, anthropogenic landscapes still sustain much biodiversity. Our question was, whether ten year changes in regional Odonata faunas are comparable between farmland and forested areas, or if the species pool of farmland areas respond in other ways than that of forest.2. We used data of dragonfly larvae collected from 16 lakes in a farmland area in south-western Sweden in the years 2002 and 2011/12, and compared these to data from 34 lakes in a forest area in south-eastern Sweden in the years 1996 and 2006.3. The species-richness in the agricultural region increased by 17% but decreased by 13% in the forested region. The changes in occurrence and regional distribution were similar in both areas, affecting 71% and 69% of the species pool. Average extinction rates were comparable between the agricultural and the forested region (38% and 43%) while colonisation rates differed greatly (64% and 114%).4. The species composition differed between the regions; the forest lakes harboured a 29% larger species pool. It is possible that in the forested region, the regional species pool in areas surrounding the study sites could stabilise the extinction and have a positive effect on changes in species composition. We assume that the different habitat structures of the waters in the agricultural and the forest regions and changes in temperature are the main driving forces behind the shifts. The mean seasonal air temperature has increased by circa 0.5°C in both regions, when comparing ten-year periods before each sampling year.
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| 3. |
- Koch, Kamilla, et al.
(författare)
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Morphological differences in the ovary of Libellulidae (Odonata)
- 2009
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Ingår i: International Journal of Odonatology. - Oxford : Taylor & Francis. - 1388-7890 .- 2159-6719. ; 12:1, s. 147-156
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Tidskriftsartikel (refereegranskat)abstract
- All female Odonata have been assumed to produce oocytes continuously during their mature life span. However, a recent study of ovariole orientation and development led to the suggestion that Libellulidae are divided into two groups of species, one with continuous, the other with stepwise oocyte production. To find more evidence of this division, we compared the size variation and growth within the vitellarium of the ovary, studying oocytes, and follicle cells. We found that morphological characters discriminate between the two ovary types in eight of the 10 investigated species. In both types we found an increase in all measurements from the anterior to the posterior end of the vitellarium. The increase in oocyte width and follicle cell length was significantly higher in species with a continuous oocyte production. We also noted that follicle cells may have more than one nucleus and that their number can vary during vitellogenesis. Our study confirmed the hypotheses that two different ovary types exist in Libellulidae. The two species not fitting into this grouping could be an artefact of small samp le size due to intraspecific phenotypic plasticity, or else there might be more than two ovary groups, or even a continuum. We could not offer an explanation as to how the process of stepwise oocyte production differs from continuous based production on morphological characters.
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| 4. |
- Koch, Kamilla, et al.
(författare)
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Morphology of follicle cells of Libellulidae (Odonata)
- 2011
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Ingår i: International journal of odonatology. - Leiden : Backhuys. - 1388-7890 .- 2159-6719. ; 14:3, s. 257-267
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Tidskriftsartikel (refereegranskat)abstract
- In libellulids, mature oocyte size varies within and between individual ovaries. The regulating mechanism is not yet understood. Variations in the contents of the follicle cells, and thereby their ability to secrete material into the oocyte, might explain some of the observed differences in oocyte size. We therefore investigated the follicle cell surface, the interstitial space width between follicle cells and between follicle cells and oocytes, the number of nuclei, and the cell compartment proportions using scanning and transmission electron microscopy. In all investigated species, the follicle cells were covered by a basal lamina. We found cytoplasmic microvilli and septate junctions. As we could not find any pores or other structures on the cell surface, endocytosis seems to be the only mechanism transporting material into the follicle cells. Larger follicle cells had larger interstitial gaps between follicle cells and oocytes, larger nuclei and a larger mitochondrial area. Larger interstitial spaces between follicle cells and oocytes may afford more room that can be filled with material from the follicle cell layer. More mitochondria could provide more energy/ATP needed for the transport of the material. The quantity of free ribosomes and the mean number of nuclei seemed to be even more important to the productivity of the follicle cell. All these variations in cell contents cause productivity differences among follicle cells and may explain some of the size differences between oocytes within individual ovaries in libellulids.
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| 5. |
- Raffard, Allan, et al.
(författare)
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Does range expansion modify trait covariation? : A study of a northward expanding dragonfly
- 2020
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Ingår i: Oecologia. - : Springer-Verlag New York. - 0029-8549 .- 1432-1939. ; 192:2, s. 565-575
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Tidskriftsartikel (refereegranskat)abstract
- The adaptive value of correlations among phenotypic traits depends on the prevailing environmental conditions. Differences in selection pressures during species range expansions may therefore shape phenotypic integration. In this study, we assessed variation in behavioral and morphological traits, as well as their covariations, in replicated southern and northern European populations of the northward expanding dragonfly Crocothemis erythraea. Larvae from northern populations were, on average, darker in color, and therefore, better camouflaged than larvae from southern populations. However, there was no difference in activity level. Darkness and activity were positively correlated in larvae from northern populations, whereas this trait covariation was missing in southern populations. This suggests the emergence of alternative strategies in time-limited northern populations, a higher activity level that required better camouflage through darker coloration, while less active larvae benefited from an energy-saving strategy by reducing the investment in costly traits, such as body darkness. We further found that larger larvae emerged into larger adults, with a higher investment in flight morphology. Our findings imply that phenotypic integration is associated with the northward range shift, potentially differentially shaping fitness consequences, and ecological interactions in southern versus northern populations.
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| 6. |
- Reuten, Raphael, et al.
(författare)
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Basement membrane stiffness determines metastases formation
- 2021
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122.
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Tidskriftsartikel (refereegranskat)abstract
- The basement membrane (BM) is a special type of extracellular matrix and presents the major barrier cancer cells have to overcome multiple times to form metastases. Here we show that BM stiffness is a major determinant of metastases formation in several tissues and identify netrin-4 (Net4) as a key regulator of BM stiffness. Mechanistically, our biophysical and functional analyses in combination with mathematical simulations show that Net4 softens the mechanical properties of native BMs by opening laminin node complexes, decreasing cancer cell potential to transmigrate this barrier despite creating bigger pores. Our results therefore reveal that BM stiffness is dominant over pore size, and that the mechanical properties of ‘normal’ BMs determine metastases formation and patient survival independent of cancer-mediated alterations. Thus, identifying individual Net4 protein levels within native BMs in major metastatic organs may have the potential to define patient survival even before tumour formation. The ratio of Net4 to laminin molecules determines BM stiffness, such that the more Net4, the softer the BM, thereby decreasing cancer cell invasion activity.
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| 7. |
- Vasiliu, Anca, et al.
(författare)
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Tuberculosis incidence in foreign-born people residing in European countries in 2020
- 2023
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Ingår i: Eurosurveillance. - : European Centre for Disease Prevention and Control (ECDC). - 1025-496X .- 1560-7917. ; 28:42
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Tidskriftsartikel (refereegranskat)abstract
- Background: European-specific policies for tuberculosis (TB) elimination require identification of key populations that benefit from TB screening.Aim: We aimed to identify groups of foreign-born individuals residing in European countries that benefit most from targeted TB prevention screening.Methods: The Tuberculosis Network European Trials group collected, by cross-sectional survey, numbers of foreign-born TB patients residing in European Union (EU) countries, Iceland, Norway, Switzerland and the United Kingdom (UK) in 2020 from the 10 highest ranked countries of origin in terms of TB cases in each country of residence. Tuberculosis incidence rates (IRs) in countries of residence were compared with countries of origin.Results: Data on 9,116 foreign-born TB patients in 30 countries of residence were collected. Main countries of origin were Eritrea, India, Pakistan, Morocco, Romania and Somalia. Tuberculosis IRs were highest in patients of Eritrean and Somali origin in Greece and Malta (both > 1,000/100,000) and lowest among Ukrainian patients in Poland (3.6/100,000). They were mainly lower in countries of residence than countries of origin. However, IRs among Eritreans and Somalis in Greece and Malta were five times higher than in Eritrea and Somalia. Similarly, IRs among Eritreans in Germany, the Netherlands and the UK were four times higher than in Eritrea.Conclusions: Country of origin TB IR is an insufficient indicator when targeting foreign-born populations for active case finding or TB prevention policies in the countries covered here. Elimination strategies should be informed by regularly collected country-specific data to address rapidly changing epidemiology and associated risks.
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| 8. |
- Ware, Jessica, et al.
(författare)
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Evolution of reproductive strategies in libellulid dragonflies (Odonata: Anisoptera)
- 2012
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Ingår i: Organisms Diversity & Evolution. - Heidelberg : Springer Science and Business Media LLC. - 1618-1077 .- 1439-6092. ; 12:3, s. 313-323
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Tidskriftsartikel (refereegranskat)abstract
- In Libellulidae, oocyte production has been assumed to be continuous, with periods of egg-laying interspersed with periods of resting/eating; however, recent work suggests that two types of oocyte production are common: either (a) continuous or (b) step-wise. These are mirrored in the arrangement of the ovarioles in the ovaries. Likewise, two types of mate-guarding behavior have been observed in Libellulidae: (1) non-contact guarding and (2) tandem guarding in which the male either hovers above the female or is physically attached to her during oviposition. Using molecular (mitochondrial and nuclear) data we explored the evolution of female reproductive traits, focusing on ovariole morphology, as well as guarding behavior, in Libellulidae. Continuous egg production appears to have evolved more than once, as have tandem and non-contact guarding. We discuss how the evolution of different ovariole types and guarding behavior may have been influenced by habitat instability, dispersal and crowded oviposition sites; thus, migratory behavior or habitat availability may have been the driving force of ovariole evolution.
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