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排序方式: 共有240条查询结果,搜索用时 15 毫秒
1.
南京汤山驼子洞洞穴堆积中鬣狗粪化石含有相对丰富的孢粉,推测草食性哺乳动物食用带有孢粉的植物后,经鬣狗的猎杀、摄食、消化和排泄,孢粉较好地保存在鬣狗粪中,形成粪化石,成为洞穴地层的组成部分。虽然鬣狗粪化石中的孢粉含量不及湖沼相地层中丰富,但有几种植物的花粉保存较好且相对集中,如Pinus,Tsuga,Quercus,Carpinus,Artemisia,Cyperaceae,Polygonum,Polypodiaceae出现的频率较高。孢粉组合揭示早更新世南京地区植被主要是草原或森林-草地,气候凉干或半干旱半湿润,可以和地层中脊椎动物群反映的自然环境相互印证。在研究洞穴古环境的代用指标中,堆积物中的鬣狗粪化石中包含的孢粉是比较好的研究对象,对环境有一定的指示意义。 相似文献
2.
Courtney M. Franssen Michael Tobler Rüdiger Riesch Francisco J. García de León Ralph Tiedemann Ingo Schlupp Martin Plath 《Aquatic Ecology》2008,42(4):685-692
A prominent trade-off in life history theory and evolution balances the costs of reproduction with those of basic somatic
needs. Hence, reproductive efforts may be reduced in environments where additional energy is required for somatic maintenance.
Here, we investigated male sperm stores in Atlantic mollies (Poecilia mexicana) from a sulfidic cave and several sulfidic and non-sulfidic surface habitats. We found significant differences among populations
in the number of sperm stripped per male, which was also correlated with differences in gonad weights. The largest sperm stores
were detected in males from non-sulfidic surface creeks, while males from a partially sulfidic surface system had lower sperm
counts, and males from completely sulfidic systems, surface as well as subterranean, had even fewer available sperm. We conclude
that the extreme environmental conditions in sulfidic habitats appear to constrain male sperm production, since hydrogen sulfide
as a naturally occurring toxin requires energy-demanding adaptations. Furthermore, we examined sperm counts of lab-reared
cave and surface mollies in response to energy limitation. Males from stock populations were placed under high and low food
treatments for a 2-week period and then stripped of sperm. Sperm counts of surface mollies tended to be reduced by low food
availability, whereas sperm counts of cave mollies did not significantly vary between food treatments, which likely points
towards a higher starvation resistance in cave mollies. 相似文献
3.
The lands including Cave Spring and most of northwest Georgia were held by the Cherokee until Cherokee removal in 1838. In 2010, a two-story pine structure that was encased inside the Green Hotel in downtown Cave Spring, Georgia, was revealed during renovation. Local Cave Spring historians insist the log structure was built by Avery Vann in 1810, making it a Cherokee structure. However, the Gold Lottery maps of 1832 show no structure on lot 871, which today contains the Green Hotel. A construction date also cannot be verified by historical documents, maps, or artifacts discovered around the Green Hotel. The purpose of this research was to determine the construction date of the Green Hotel log structure. Archaeological dating of the window glass thickness of the hotel gave dates of 1810 or 1823. However, the dendroarchaeological dating of the wood indicates cutting dates during the late spring/early summer of 1839. This would indicate that the log structure inside the Green Hotel was not built by Avery Vann or any Cherokee, but by later Euro-American settlers. 相似文献
4.
A. J. McLachlan 《Hydrobiologia》1977,54(3):195-199
The troglobitic amphipod crustacean Crangonyx antennatus occupies mud-bottom pools and small, gravel-bottom streams in caves in the southern Appalachians. One large, mud-bottom pool
population in Lee Co., Virginia was observed periodically from 1967 to 1975. Amphipods in this population frequently burrowed
into the soft mud substrate, where they were able to survive desiccation during periods when the pool dried up. Animals kept
in the laboratory also burrowed and survived desiccation during an experiment which simulated drought conditions similar to
those observed in caves. Amphipods collected from both pool and stream habitats burrowed, thereby indicating that stream-adapted
populations of this species still retain sufficient flexibility to survive under variable environmental conditions that might
be encountered in nature. It is concluded that burrowing provides a means of survival for C. antennatus when it is sometimes exposed to drought conditions in cave pool habitats and also provides protection from potential terrestrial
predators under similar conditions. Burrowing also offers amphipods protection from aquatic predators (such as salamander
larvae) during normal water levels and possibly allows juveniles a means of escaping cannibalism by adults. 相似文献
5.
周口店田园洞古人类化石点的无颈鬃豪猪(Hystrix subcristata) 总被引:7,自引:1,他引:6
周口店田园洞位于北京猿人遗址西南6km处,是新发现的晚期智人化石地点。该地点是迄今我国北方地区第四纪化石地点中含豪猪材料最丰富的。从头骨、牙齿、头后骨骼的形态特征及大小判断,田园洞的豪猪应归入我国现生无颈鬃豪猪(Hystrixsubcristata)。14C测年表明,含豪猪化石的地层时代为3.05~0.467万年,为更新世末期到全新世中期,是目前所知豪猪化石在我国北方地区的最晚记录。 相似文献
6.
The gypsum karst of the western Ukraine developed largely under artesian conditions. The Miocene aquifer is presently entrenched and dewatered over much of the territory, while it remains confined in the zone adjacent to the Carpathian Foredeep. The most prominent geochemical features of the Miocene aquifer system in the confined karst zone are: (1) the almost universal presence of a bioepigenetic calcite bed, enriched in the light carbon isotope, at the top of the gypsum (the "Ratynsky Limestone"), (2) the widespread sulfur mineralization associated with the above calcite bed (the region is one of the world's largest sulfur-bearing basins), and (3) high H 2 S and CO 2 in the groundwater. Intense microbial sulfate-reduction processes occur in the gypsum in this zone. Zoloushka Cave is the third longest (92 km) and the largest by volume (more than 7 2 10 5 m 3 ) gypsum cave in the world. It is a unique example of a young artesian cave that only during the Holocene became partly drained and during the last 50 years progressively dewatered due to a quarry operation. These rapid changes have induced a number of transitional geochemical processes, some of which appear to be bacterially mediated. Six groups of microorganisms have been identified in the cave. Our article discusses the aquifer geochemistry during the transitional stage in the light of the microbiological studies. 相似文献
7.
Guanjun Shen Xianzhu Wu Qian Wang Hua Tu Yue-xing Feng Jian-xin Zhao 《Journal of human evolution》2013
Most researchers believe that anatomically modern humans (AMH) first appeared in Africa 160-190 ka ago, and would not have reached eastern Asia until ∼50 ka ago. However, the credibility of these scenarios might have been compromised by a largely inaccurate and compressed chronological framework previously established for hominin fossils found in China. Recently there has been a growing body of evidence indicating the possible presence of AMH in eastern Asia ca. 100 ka ago or even earlier. Here we report high-precision mass spectrometric U-series dating of intercalated flowstone samples from Huanglong Cave, a recently discovered Late Pleistocene hominin site in northern Hubei Province, central China. Systematic excavations there have led to the in situ discovery of seven hominin teeth and dozens of stone and bone artifacts. The U-series dates on localized thin flowstone formations bracket the hominin specimens between 81 and 101 ka, currently the most narrow time span for all AMH beyond 45 ka in China, if the assignment of the hominin teeth to modern Homo sapiens holds. Alternatively this study provides further evidence for the early presence of an AMH morphology in China, through either independent evolution of local archaic populations or their assimilation with incoming AMH. Along with recent dating results for hominin samples from Homo erectus to AMH, a new extended and continuous timeline for Chinese hominin fossils is taking shape, which warrants a reconstruction of human evolution, especially the origins of modern humans in eastern Asia. 相似文献
8.
《Chronobiology international》2013,30(10):1336-1344
Arachnocampa species, commonly called glowworms, are flies whose larvae use light to attract prey. Here we compare rhythmicity in two of the nine described species: the Tasmanian species, Arachnocampa tasmaniensis, which inhabits caves and wet forest, and the eastern Australian mainland species, A. flava, primarily found in subtropical rainforest. Both species show the same nocturnal glowing pattern in external (epigean) environments and the same inhibition of bioluminescence by light and both species show circadian regulation of bioluminescence. We find that the underlying circadian bioluminescence propensity rhythm (BPR) of the two species peaks at opposite phases of the day:night cycle. Larvae of A. flava, placed in constant darkness in the laboratory, bioluminesce during the subjective scotophase, typical of nocturnal animals, whereas A. tasmaniensis shows the opposite tendency, bioluminescing most intensely during the subjective photophase. In A. tasmaniensis, which are exposed to natural day:night cycles, light exposure during the day overrides the high bioluminescence propensity through negative masking and leads to a release of bioluminescence after dusk when the BPR is on the wane. A consequence is that A. tasmaniensis is able to start glowing at any phase of the light:dark cycle as soon as masking by light is released, whereas A. flava is locked into nocturnal bioluminescence. We suggest that the paradoxical BPR of A. tasmaniensis is an adaptation for living in the cave environment. Observations of bioluminescence in colonies of A. tasmaniensis located in the transition from a cave mouth to the dark zone show that glowing is inhibited by light exposure but a peak bioluminescence follows immediately after “dusk” at their location. The substantial difference in the circadian regulation of bioluminescence between the two species probably reflects adaptation to the cave (hypogean) habitat in A. tasmaniensis and the forest (epigean) habitat in A. flava. (Author correspondence: d. merritt@uq. edu. au) 相似文献
9.
Cajus G. Diedrich 《Historical Biology》2013,25(2-3):271-311
Remains of 13 individuals with 3/1 male/female ratio of the extinct Upper Pleistocene lion Panthera leo spelaea (Goldfuss, 1810) from the Zoolithen Cave near Burggeilenreuth (Bavaria, Germany) include the holotype skull and all paratype material. The highest mortality rate for the Zoolithen Cave lions is in their reproductive adult ages. Bite marks on lion bones or skulls are results of hyena activities, or rare cannibalism of lions under stress situations. Lions were possibly also killed in battles with cave bears during predation on hibernating bears in winter times. This cave bear hunt specialisation in caves overlaps with the ecological behaviour of cave bear feeding by Ice Age-spotted hyenas. Both largest Ice Age predators, lions and hyenas, had to specialise on feeding herbivorous cave bears in boreal forest mountainous cave rich regions, where the mammoth steppe megafauna prey was absent. This cave bear hunt by felids, and scavenging by hyenas and other large carnivores such as leopards and wolves explains why cave bears hibernated deep in to the European caves, for protection reasons against predators. Within such lion–cave bear and even lion–hyena conflicts in the caves lions must have been killed sometimes, explaining mainly the skeleton occurrences in different European caves. 相似文献
10.
Cajus G. Diedrich 《Historical Biology》2013,25(2):161-185
A Late Pleistocene spotted hyena Crocuta crocuta spelaea (Goldfuss 1823) population from the cave bear den Sloup Cave, Moravia (Czech Republic) consists of mainly adult/senior and few cub/juvenile remains and coprolites, and 139 prey bones. Hyenas used the Nicová Cave branch that is connected to the entrance area mainly as a communal den site. Prey bone damage is most visible on the imported woolly rhinoceros remains. The partly excavated prey bone accumulation consists of a single woolly mammoth Mammuthus primigenius (Blumenbach 1799) tooth (2%), mainly Coelodonta antiquitatis (Blumenbach 1807) remains (16%), 4% Bos primigenius (Bojanus 1827) and 1% each of Megaloceros giganteus (Blumenbach 1799) and Rangifer tarandus (Linnaeus 1758). The other carnivores such as Panthera leo spelaea (Goldfuss 1810), Gulo gulo (Linnaeus 1758) and Canis lupus (Linnaeus 1758) subsp. are less represented (1–3%). Wolverines might have been imported also as prey remains, whereas wolves also possibly used this cave on a short-term basis, whereas steppe lions seem to have preyed upon cave bears deeper in the cave periodically, where even skeletons of P. leo spelaea were found in the Elisabeth Cave part. 相似文献