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461.
462.
Female control of extra-pair fertilization in tree swallows 总被引:4,自引:0,他引:4
Summary In a Canadian population of tree swallows, Tachycineta bicolor, DNA fingerprinting has previously shown that half of all broods contain many offspring resulting from extra-pair copulations (EPCs), whereas the other half contain only legitimate offspring. This bimodal pattern of extra-pair paternity might be due to variation in the effectiveness of male paternity guards, variation in female ability to resist EPCs, and/or variation in female pursuit of EPCs. Here we report experimental evidence for female control of copulations and fertilizations and the occurrence of two alternative copulation strategies among females in this population. Ten paired male tree swallows were removed on the day their mates laid the first egg. Replacement males took over the nestbox within 0.5–23 h and attempted to copulate with the widowed female. Assuming that eggs were fertilized approximately 24 h prior to laying, the first two eggs were fertilized before the male was removed, while the third and subsequent eggs could potentially be fertilized by the replacement male. Fingerprinting revealed that the first two eggs were sired by the resident males in five nests and by extra-pair males in the remaining five nests. The widows that had been faithful to their initially chosen mate rejected copulation attempts by the replacement male until most of the eggs had been laid. Consequently, nearly all eggs laid by these females were sired by the original male. The widows that had been unfaithful prior to male removal copulated sooner with the replacement male than females that were faithful to their mate. However, these replacement males also had a very low fertilization success; most eggs were sired by males that were not associated with the nest. This is consistent with the situation in non-experimental nests where unfaithful females copulate with their mate at the same rate as faithful females, yet unfaithful females have a majority of offspring sired by extra-pair males. We conclude that fertilization patterns to a large extent are determined by the female through active selection and rejection of copulation partners, though our results also allow some speculation that females have control over sperm competition. Female copulation tactics are probably determined some currently unknown fitness benefits of having the offspring sired by particular males.Correspondence to: Raleigh J. Robertson 相似文献
463.
Antoon Opperhulzen Els W. v. d. Volde Frank A. P. C. Gobas Djlen A. K. Liem Jan M. D. v. d. Steen 《Chemosphere》1985,14(11-12)
Most polychlorinated naphthalones (PCN) accumulate rapidly according to their hydrophobicity. The uptake and ellmination rate constants are comparable to those of chlorinated benzenes and biphenyls.For most PCN-congeners the resulting bioaccumulation factors show an increase with increasing hydrophobicity. For higher Kd,oct-values (>105) however, no further increase of Kc is observed (Kc. max. = 3.5.104).For the two hepta- and the octachloronaphthalenes no detectable concentrations are found in the fishes, although no restricted blo-availability could be expected. Based on these observations and on data obtained from the literature. a loss of membrane permeation is suggested for hydrophobic molecules with widths over 9.5 Å.In addition a membrane permeation model, as part of the accumulation process of hydrophobic chemicals. Is proposed, which is based on diffusion and partition processes. 相似文献
464.
Brian P. Leaderer Jan A. J. Stolwijk Rebecca T. Zagraniski 《Environmental management》1977,1(2):131-137
A method is presented by which an upper limit of the adverse health effect of existing ambient CO concentrations on the U. S. population can be estimated. The method is based upon estimating the primary human physiological response to CO concentrations (COHb%) for the population in terms of person-hour-COHb>1.5% resulting from the time exposure of the population to CO concentrations in excess of the federally designated ambient air quality standard. The estimates of person-hour-COHb>1.5% are for exposures only to ambient CO concentrations and do not take into account the additional CO exposure for people who smoke or have occupational exposures.We estimate that there were up to 30.9×109 person-hour-COHb>1.5% in 1973 due to ambient concentrations in excess of the ambient 8-hour CO standard, with approximately 5×109 person-hour-COHb>1.5% occurring West of the Continental Divide and 25.9>109 person-hour-COHb>1.5% occuring East of the Continental Divide; of these 21.3×109 personhour-COHb>1.5% occurred in New York City. It was also estimated that a 60% reduction in 1973 ambient concentrations of CO (corresponding to an automotive emmision standard of less than 15 g/mile) would be needed to reduce to zero the person-hour-COHb>1.5%. The maximum estimated effects on the U.S. population of increases in ambient CO concentration above 1973 levels are also presented. 相似文献
465.
Jan D. Schmitt-Tegge 《Die Naturwissenschaften》1980,67(4):182-187
Special problems of treatment of hazardous wastes in the Federal Republic of Germany are discussed (i.e., evaluation of the manifest system, “hazardous-waste processes”, control). Special processes (incineration at sea, dumping, deep-well injection) are presented. The second part is a report about the congress of the American Chemical Society in Honolulu in April 1979, i.e., about the U.S. EPA Hazardous-Waste Program, about the abandoned hazardouswaste disposal sites and about several stabilization and solidification processes. 相似文献
466.
467.
Jan Thesing 《Die Naturwissenschaften》1977,64(12):601-605
The author gives a breakdown of costs for industrial drug research and development of seven German drug companies. Trends of development and fields of interdisciplinary pharmaceutical research are described. Increasing expenditures and requirements for safety and efficacy reduce the chances of innovation. 相似文献
468.
We evaluated first-trimester maternal serum alpha-fetoprotein (MS-AFP) as a marker for fetal chromosomal disorders. The multicentre study was performed under the auspices of the Dutch Working Party on Prenatal Diagnosis. MS-AFP was measured in 2404 normal pregnancies and 72 chromosomally abnormal pregnancies. The median multiple of the normal median (MOM) in 32 Down's syndrome pregnancies was 0·83 with a 95 per cent confidence interval ranging from 0·60 to 1·04. The difference between the distributions of first-trimester MS-AFP in normal and Down's syndrome pregnancies was statistically significant (t-test: t = 2·34, P<0·05). Thirty-one per cent of the Down's syndrome pregnancies were found below the tenth percentile. We found no difference between normal pregnancies and pregnancies with other chromosomal disorders (eight cases with trisomy 18, MOM = 1·26; seven cases with sex chromosome abnormalities, MOM = 1·07; 22 cases with a chromosomal mosaic pattern in chorionic villi, MOM = 1·08). We conclude that first-trimester MS-AFP can discriminate between normal and Down's syndrome pregnancies, but is not an effective marker. First-trimester MS-AFP has no value as a marker for other fetal chromosomal disorders. 相似文献
469.
Rodríguez I Gumbert A Hempel de Ibarra N Kunze J Giurfa M 《Die Naturwissenschaften》2004,91(8):374-377
Bilateral symmetry has been considered as an indicator of phenotypic and genotypic quality supporting innate preferences for highly symmetric partners. Insect pollinators preferentially visit flowers of a particular symmetry type, thus leading to the suggestion that they have innate preferences for symmetrical flowers or flower models. Here we show that flower-naïve bumblebees (Bombus terrestris), with no experience of symmetric or asymmetric patterns and whose visual experience was accurately controlled, have innate preferences for bilateral symmetry. The presence of color cues did not influence the bees original preference. Our results thus show that bilateral symmetry is innately preferred in the context of food search, a fact that supports the selection of symmetry in flower displays. Furthermore, such innate preferences indicate that the nervous system of naïve animals may be primed to respond to relevant sensory cues in the environment. 相似文献
470.
螯合树脂富集——原子荧光法测定地面水中的痕量汞 总被引:2,自引:0,他引:2
经对数种不同功能团螯合树脂的研究,优选出了对尔吸附效率高,解脱速度快的H-1S8型螯合树脂,并对树脂装填柱的形态及体积大小进行了研究。经脂交换与洗脱条件及原子荧光谱测试条件进行了优化实验。实验结果,方法的检出限为0.002μg/L,测定地面水水样汞的平均浓度为0.009μg/L;精密度实验的相对标准偏差为5.5%,回收率为96-101% 相似文献