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1.
Bird specimens collected by 19th century explorer and ornithologist Prince Maximilian of Wied-Neuwied form one of the foundation collections of the American Museum of Natural History in New York. However, parts of his collection remained in Germany and came to the Museum Wiesbaden. Since Wied described numerous new species without designating types, some of these specimens might be type material. Here we present a catalog of the 30 Wiesbaden specimens associated with him and discuss their potential type status. We conclude that 17 individuals in 11 species are potential type specimens that should be considered in future taxonomic work. 相似文献
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The maturation of zygotes formed by the fusion of two gametes is the essential part of the diploid phase of the Chlamydomonas reinhardtii sexual life cycle and results in mature zygotes competent to germinate. To understand the molecular mechanisms underlying zygote maturation and the attainment of competence for germination we isolated genomic clones representing three different genes that are specifically expressed in Chlamydomonas reinhardtii zygotes. Accumulation of the RNAs started more than 24 h after mating, setting these genes apart from genes expressed in young zygotes [9]. Upon light-induced germination of zygotes, the mRNAs disappeared. The patterns of RNA accumulation and disappearance were gene-specific and suggested a function of these genes in maturation and/or in initial steps of germination. 相似文献
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Jan-Wolfhard Kellmann Tatjana Kleinow Kerstin Engelhardt Christina Philipp Dorothee Wegener Jeff Schell Peter H. Schreier 《Plant molecular biology》1996,30(2):351-358
Two different genes encoding class II chitinases from peanut (Arachis hypogaea L. cv. NC4), A.h.Chi2;1 and A.h.Chi2;2, have been cloned. In peanut cell suspension cultures, mRNA levels of A.h.Chi2;2 increased after ethylene or salicylate treatment and in the presence of conidia from Botrytis cinerea. The second gene, A.h.Chi2;1, was only expressed after treatment with the fungal spores. Transgenic tobacco plants containing the complete peanut A.h.Chi2;1 gene exhibited essentially the same expression pattern in leaves as observed in peanut cell cultures. Expression characteristics of transgenic tobacco carrying a promoter-GUS fusion of A.h.Chi2;1 are described. 相似文献
6.
Andreas Christian Dorothee Koberg Holger Preuschoft 《Pal?ontologische Zeitschrift》1996,70(3-4):591-601
The pelvis ofPlateosaurus is examined from a biomechanical point of view. The shape of the acetabulum in particular is analysed in order to determine the range of possible directions of the forces exchanged between femur and pelvis. These forces must have been more or less confined to a sagittal plane. From a quasi-static analysis under consideration of the major hip muscles ofPlateosaurus, a nearly but not fully extended posture of the hindlimbs can be deduced. The hip joints ofPlateosaurus and probably of some other dinosaurs with a narrow biacetabular width were balanced rather by adducting than by abducting muscles. 相似文献
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Dorothee Hodapp Irene T. Roca Dario Fiorentino Cristina Garilao Kristin Kaschner Kathleen Kesner-Reyes Birgit Schneider Joachim Segschneider Ádám T. Kocsis Wolfgang Kiessling Thomas Brey Rainer Froese 《Global Change Biology》2023,29(12):3304-3317
Driven by climate change, marine biodiversity is undergoing a phase of rapid change that has proven to be even faster than changes observed in terrestrial ecosystems. Understanding how these changes in species composition will affect future marine life is crucial for conservation management, especially due to increasing demands for marine natural resources. Here, we analyse predictions of a multiparameter habitat suitability model covering the global projected ranges of >33,500 marine species from climate model projections under three CO2 emission scenarios (RCP2.6, RCP4.5, RCP8.5) up to the year 2100. Our results show that the core habitat area will decline for many species, resulting in a net loss of 50% of the core habitat area for almost half of all marine species in 2100 under the high-emission scenario RCP8.5. As an additional consequence of the continuing distributional reorganization of marine life, gaps around the equator will appear for 8% (RCP2.6), 24% (RCP4.5), and 88% (RCP8.5) of marine species with cross-equatorial ranges. For many more species, continuous distributional ranges will be disrupted, thus reducing effective population size. In addition, high invasion rates in higher latitudes and polar regions will lead to substantial changes in the ecosystem and food web structure, particularly regarding the introduction of new predators. Overall, our study highlights that the degree of spatial and structural reorganization of marine life with ensued consequences for ecosystem functionality and conservation efforts will critically depend on the realized greenhouse gas emission pathway. 相似文献
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Induction of diapausing amictic eggs in Synchaeta pectinata 总被引:2,自引:0,他引:2
Amictic females of a clone of S. pectinata from Star Lake (Norwich, Vermont) may produce diapausing as well as non-diapausing (subitaneous) eggs. The proportion of diapausing eggs produced in cultures was unaffected by temperature (12 vs 19 °C) or rotifer population density (minima of 0.33 vs 3 ind. ml–1) at 19 °C. However, at 19 °C this proportion was higher in cultures maintained at a low food level suppressing reproduction (5 × 103 cells ml–1
Cryptomonas erosa) than in those maintained at a high food level (2 × 104 cells ml–1); the treatment effect was marginally significant (p=0.067). Consistent with the effect of low food availability, a period of starvation was very effective in inducing the development of diapausing eggs. None of 19 females cultured individually from hatching at 19 °C on C. erosa (2 × 104 cells ml–1) in 1-ml volumes produced any diapausing eggs in 4 days (0 out of 349 eggs), while 13 out of 16 females subjected to a 15-hour starvation period 6 hours after birth produced one or more diapausing eggs during that time (34% of the 158 eggs produced by the 16 females were diapausing). Diapausing eggs produced and left at 19 °C hatched after 4 to 13 days. Those produced in cultures with a low food level took significantly longer to hatch (9.7 days) than those produced in cultures with a high food level (8.1 days) (p=0.022). In natural communities, S. pectinata should be able to respond directly and rapidly to poor food conditions by producing eggs that undergo an obligatory dormant period before resuming development. 相似文献
10.
M Ehrich J E Aswell R L van Tassell T D Wilkins A R Walker N J Richardson 《Mutation research》1979,64(4):231-240
The incidence of mutagens in the feces of 3 South-African populations at different risk levels for colon cancer has been determined. Lyophilized fecal samples were extracted with ether and the mutagenicity of the extracts determined using the Salmonella/mammalian microsome mutagenicity test. 19% of the samples from urban white South-Africans, a population at a high risk for colon cancer, were mutagenic using Salmonella typhimurium strain TA100. This incidence was significantly greater (p less than 0.001) than the incidence of mutagen excretion in the low-risk populations of urban blacks (2%) and rural blacks (0%). This pattern was also obtained using Salmonella typhimurium strain TA98. The incidence of mutagen excretion for urban whites was 10%, as compared to 5% and 2% for urban and rural blacks, respectively. 相似文献