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31.
Terje Laskemoen Oddmund Kleven Frode Fossøy Raleigh J. Robertson Geir Rudolfsen Jan T. Lifjeld 《Behavioral ecology and sociobiology》2010,64(9):1473-1483
Sperm competition is widespread among animal taxa and considered a major force in sperm evolution. Recent comparative studies have indicated that sperm competition selects for high sperm production capacity and long and fast-swimming spermatozoa across species. Here, we examine the role of sperm quantity and quality for fertilization success of individual males in a Canadian population of tree swallows Tachycineta bicolor, a socially monogamous, but highly promiscuous passerine. Male fertilization success (the sum of withinpair and extrapair young) was significantly associated with the size of the cloacal protuberance (a proxy for sperm quantity), but not with sperm size or in vitro sperm swimming speed. In a multivariate analysis, both cloacal protuberance volume and relative sperm midpiece size (i.e. high mitochondrial loading) had significant effects on male fertilization success. However, relative sperm midpiece size was not associated with fertilization success in a simple regression. Further, both cloacal protuberance volume and relative midpiece size had significant effects on sperm velocity, both in simple regressions and in a multivariate analysis. The finding that males with large relative midpiece size had both higher fertilization success and faster swimming sperm, suggests an indirect link between sperm morphology and male fertility mediated through sperm velocity. In conclusion, both quantitative and qualitative sperm traits seem to affect male fertilization success in tree swallows. 相似文献
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Silje Hogner Terje Laskemoen Jan T. Lifjeld Václav Pavel Bohumír Chutný Javier García Marie-Christine Eybert Ekaterina Matsyna Arild Johnsen 《Behavioral ecology and sociobiology》2013,67(8):1205-1217
Spermatozoa are among the most variable animal cell types, and much research is currently directed towards explaining inter- and intraspecific variation in sperm form and function. Recent comparative studies in passerine birds have found associations between the level of sperm competition and both sperm length and sperm velocity. In species with sperm competition, postcopulatory sexual selection may shape the morphology of sperm as adaptations to the female environment. The speed of evolutionary change in sperm morphology at the species level is largely unknown. In this study, we analysed variation in sperm morphology among morphologically distinct and geographically isolated bluethroat subspecies in Europe. Consistent with previous studies, our analyses of mtDNA and nuclear introns suggest recent divergence and lack of lineage sorting among the subspecies. We found significant divergence in total sperm length and in the length of some sperm components (i.e. head and midpiece). There was a significantly positive relationship between pairwise divergences in sperm morphology and mitochondrial DNA, suggesting a role for genetic drift in sperm divergence. The magnitude of sperm length divergence was considerably higher than that in other geographically structured passerines, and even higher than that observed between several pairs of sister species. We hypothesize that the rapid sperm evolution in bluethroats is driven by sperm competition, and that strong postcopulatory sexual selection on sperm traits can lead to rapid speciation through reproductive incompatibilities. 相似文献
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Terje Houeland 《Environmental geochemistry and health》1990,12(1-2):173-177
At the present time there seems to be sufficient evidence to conclude that aluminium may, at least under some circumstances, be neurotoxic. Furthermore, several studies have found increased amounts of aluminium in specific brain structures of people who have died with Alzheimer's disease. From the available evidence it is not possible, however, to draw any firm conclusions regarding the possible role of aluminium in the aetiology or pathogenesis of Alzheimer's disease.Even though there is some evidence from ecological studies that exposure to aluminium at least from drinking water may be causally linked to the development of Alzheimer's disease, it is still entirely possible that the accumulation of aluminium in the brains of people with this disorder is a secondary phenomenon. There is a lack of data relating individual exposure to aluminium with subsequent risk of developing the disease.A case-control study currently being carried out in Norway will seek to collect individual exposure data with particular emphasis on aluminium exposure from drinking water sources. The design of this study is presented. 相似文献
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Emily R. A. Cramer Terje Laskemoen Fabrice Eroukhmanoff Fredrik Haas Jo S. Hermansen Jan T. Lifjeld Melissah Rowe Glenn-Peter Sætre Arild Johnsen 《Behavioral ecology and sociobiology》2014,68(7):1133-1144
Sexual selection may drive speciation, but most research focuses on pre-copulatory sexual selection, overlooking post-copulatory processes. Post-copulatory sexual selection in allopatric populations could drive divergence in post-copulatory pre-zygotic (PCPZ) phenotypes, limiting gene flow upon secondary contact. Here, we performed in vitro experiments examining one potential PCPZ barrier between two closely related passerine species, house sparrows (Passer domesticus) and Spanish sparrows (Passer hispaniolensis). In birds, crossing in the vagina may be particularly challenging for sperm, so we tested the effect of female reproductive tract fluids on sperm swimming speed and motility. If a PCPZ barrier exists at this stage of the fertilization process, heterospecific female fluids are predicted to reduce sperm swimming speed or motility relative to conspecific female fluid. We found that house sparrow female fluids affected the two species’ sperm asymmetrically, depending on the control sperm velocity and male species. Overall, however, sperm performed equally in conspecific and heterospecific female fluids, and the species had similar sperm morphology and sperm swimming performance. Low divergence in PCPZ phenotypes between species, perhaps because post-copulatory sexual selection is stabilizing or only moderately strong in these taxa, may be insufficient to cause an overall PCPZ barrier. Reinforcement may be unlikely to drive PCPZ barriers for this species pair, because relatively effective pre-copulatory barriers exist between the species, and because hybrids can be quite successful. Testing the role of PCPZ barriers in birds with more divergent PCPZ phenotypes will improve our understanding of speciation in passerines. 相似文献
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Arild Johnsen Henrik Pärn Frode Fossøy Oddmund Kleven Terje Laskemoen Jan T. Lifjeld 《Behavioral ecology and sociobiology》2008,62(11):1761-1767
Extra-pair paternity is common in birds and much research has focussed on the selective advantage of extra-pair matings for
both sexes. In contrast, little attention has been given to the fact that in most species the majority of offspring are sired
by the social male. We investigated whether extra-pair matings of female bluethroats (Luscinia svecica) are constrained by the presence of the pair male, by detaining males in cages on their territories for one morning during
the peak of female fertility. The proportion of offspring sired by extra-pair males was higher in broods where males had been
detained (35%) than in control broods (16%), while the proportion of broods that had at least one extra-pair offspring did
not differ significantly between experimental (65%) and control broods (44%). Within the experimental group, levels of extra-pair
paternity were not related to the day of experiment in relation to start of egg laying, but males caught early in the morning
lost more paternity than males caught later on. Our results show that pair males exert constraints on the frequency of extra-pair
paternity by being present during the period of peak fertility, which could be a direct effect of their mate guarding effort
and/or due to an advantage in sperm competition for pair males. 相似文献
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Kristin Aunan Terje K. Berntsen Gunnar Myhre Kristin Rypdal David G. Streets Jung-Hun Woo Kirk R. Smith 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5674-5681
Household fuel use in developing countries, particularly as biomass and coal, is a major source of carbonaceous aerosols and other air pollutants affecting health and climate. Using state-of-the-art emission inventories, a global three-dimensional photochemical tracer/transport model of the troposphere, and a global radiative transfer model based on methods presented in the latest IPCC Assessment Report (2007-AR4), we estimate the radiative forcing (RF) attributable to household fuel combustion in Asia in terms of current global annual-mean RF and future global integrated RF for a one-year pulse of emissions (2000) over two time horizons (100 and 20 years). Despite the significant emissions of black carbon (BC) aerosols, these estimates indicate that shorter-lived (non-Kyoto) air pollutants from household fuel use in the region overall seem to exert a small net negative RF because of the strong influence of reflective aerosols. There are, however, major uncertainties in emission estimates for solid fuel burning, and about the sustainability of household fuel wood harvesting in Asia (the carbon neutrality of harvesting). In addition, there is still substantial uncertainty associated with the BC radiative forcing. As a result we find that the sign of the RF from household biomass burning in the region cannot be established. While recognizing the value of integrating climate change and air pollution policies, we are concerned that for a ‘Kyoto style’ post-Kyoto treaty (with global cap-and-trade and the Global Warming Potential as the metric) expanding the basket of components with a selection of short-lived species without also including the wider range of co-emitted species may lead to unintended consequences for global-scale climate. Additional measurement, modelling, and policy research is urgently needed to reduce the uncertainties so that the net impact on climate of emissions and mitigation measures in this sector can be accurately assessed. 相似文献
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Popic JM Salbu B Strand T Skipperud L 《Journal of environmental monitoring : JEM》2011,13(6):1730-1738
The Fen Central Complex in southern Norway, a geologically well investigated area of magmatic carbonatite rocks, is assumed to be among the world largest natural reservoirs of thorium ((232)Th). These rocks, also rich in iron (Fe), niobium (Nb), uranium ((238)U) and rare earth elements (REE), were mined in several past centuries. Waste locations, giving rise to enhanced levels of both radionuclides and metals, are now situated in the area. Estimation of radionuclide and metal contamination of the environment and radiological risk assessment were done in this study. The average outdoor gamma dose rate measured in Fen, 2.71 μGy h(-1), was significantly higher than the world average dose rate of 0.059 μGy h(-1). The annual exposure dose from terrestrial gamma radiation, related to outdoor occupancy, was in the range 0.18-9.82 mSv. The total activity concentrations of (232)Th and (238)U in soil ranged from 69 to 6581 and from 49 to 130 Bq kg(-1), respectively. Enhanced concentrations were also identified for metals, arsenic (As), lead (Pb), chromium (Cr) and zinc (Zn), in the vicinity of former mining sites. Both radionuclide and heavy metal concentrations suggested leaching, mobilization and distribution from rocks into the soil. Correlation analysis indicated different origins for (232)Th and (238)U, but same or similar for (232)Th and metals As, Cr, Zn, nickel (Ni) and cadmium (Cd). The results from in situ size fractionation of water demonstrated radionuclides predominately present as colloids and low molecular mass (LMM) species, being potentially mobile and available for uptake in aquatic organisms of Norsj? Lake. Transfer factors, calculated for different plant species, showed the highest radionuclide accumulation in mosses and lichens. Uptake in trees was, as expected, lower. Relationship analysis of (232)Th and (238)U concentrations in moss and soil samples showed a significant positive linear correlation. 相似文献