Population dynamics and tolerance to desiccation in a crustacean ostracod adapted to life in small ephemeral water bodies   总被引：1，自引：0，他引：1  

Josep A. Aguilar-Alberola  Francesc Mesquita-Joanes 《Limnologica》2011,41(4):348-355

Given their small size, isolation and unpredictability, temporary rockpools present high environmental stress and impoverished communities of species that have adapted to such stressful conditions. Special adaptations of the invertebrates living in these habitats include tolerance to desiccation and fast ontogenetic development in order to maintain stable populations and face high risk of extinction. Dozens of small rockpools (mostly with Ø < 1 m) can be found in east Spain on limestone substrate, where the only known Iberian populations of Heterocypris bosniacaPetkovski et al. (2000), an ostracod species with geographic parthenogenesis, have been recently found. In this survey, two of these rockpools have been monitored during the main hydroperiod between the fall of 2005 and summer 2006 to test the ability of H. bosniaca parthenogenetic populations to face unpredictable hydroperiod dynamics. Pools were visited weekly, and limnological data and ostracod samples were obtained from either water or substrate in dry periods. Ostracod individuals were counted and assigned to growth instars to monitor population changes. In the laboratory, experimental cultures allowed the estimation of survival dependence on the substrate desiccation rate. Throughout the hydrological cycle studied, several hatching periods were observed, usually preceded by desiccation, followed by substrate hydration and water dilution by rain. The demographic changes observed indicate that H. bosniaca populations are able to persist in intermittently inundated environments and produce several generations per annual hydrological cycle. In addition, adult individuals were able to survive in the wet mud of dry pools for longer than five weeks. The experimental data suggest a lower average survival time when exposed to desiccation processes, and that the velocity of substrate water loss is a determining factor for the survival rate of ostracods resisting dry events in temporary ponds. As shown by ostracods’ life histories in temporary aquatic environments undergoing unpredictable desiccation events, a combined strategy of adult tolerance to short periods of water scarcity and rapid hatching from resting egg banks can be advantageous for the monopolization of small-sized ephemeral habitats.  相似文献   

Ostracoda during the Early Aptian (Early Cretaceous) greenhouse period on the Isle of Wight, England     

Ian P. Wilkinson 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(5):809-815

The earliest Aptian marine transgression of the Lower Cretaceous across southern England resulted in the collapse of the generally freshwater Barremian environment and the initiation of marine mileux. Salinities passed from fresh-oligohaline to meso- and pliohaline, reaching fully marine conditions during the obsoletum Subzone (P. fissicostus Zone). Newly formed environmental niches were rapidly occupied by ostracod associations. In the Isle of Wight, freshwater Cypridea-rich assemblages in the lower Shepherd's Chine Member (Vectis Formation) were gradually replaced by faunas dominated by Sternbergella cornigera, Mantelliana mantelli and Theriosynoecum fittoni. Marine taxa recorded from the Atherfield Clay Formation migrated predominantly from the Paris Basin and include Asciocythere albae, Schuleridea derooi, Neocythere gottisi, N. bordeti, Cythereis geometrica, Cytheropteron stchepinskyi and Protocythere croutesensis.  相似文献   

A new pelagic Polyconchoecia Xiang, Chen and Du, 2018 (Ostracoda: Myodocopa: Halocyprididae) from the South China Sea     

项鹏  王雨  陈瑞祥  叶又茵  王春光  陈小银  林茂 《海洋学报(英文版)》2020,39(4):73-83

Halocyprid ostracods are appreciable part of ostracods floating through virtually everywhere in marine environment.In this study,we describe a new species of genus Polyconchoecia Xiang,Chen and Du,2018,tribe Conchoeciini Chavtur and Angel,2011,family Halocyprididae Dana,1853 from the middle of the South China Sea.Polyconchoecia chenii sp.nov.is very close to P.commixtus Xiang,Chen and Du,2018.But it differs from P.commixtus by the distinctions of locations of major glands of carapace and the characteristics of appendages:more posteriorly situated left asymmetric gland of carapace,no right asymmetric gland;segmented frontal organ;the endopod 2 of the first antenna with a very small seta;a-and c-setae of the first antenna with long end joint have long end joint,the b-and d-setae have no end joint,spinose e-seta without end joint;the e-seta of the second antenna is present;teeth side is distinctive;the setal counts of the mandible,maxilla,fifth limb,and sixth limb are individual.The locations of the major glands on carapace and the characteristics of the first antenna can be the key of the new species.This work is the second discovery of the genus Polyconchoecia from the world.  相似文献   

Confirmation of an interglacial age for the Condat tufa (Dordogne,France) from biostratigraphic and isotopic data     

R. C. Preece  P. M. Thorpe  J. E. Robinson 《第四纪科学杂志》1986,1(1):57-65

The Condat tufa is a localised deposit, reaching 8.2m in thickness, composed of freshwater carbonates deposited in a complex series of environments which include marsh, spring and stream facies. Five radiocarbon determinations had previously been obtained from different stratigraphic levels within the tufa and had given a consistent series, ranging from 12320 ± 175 BP to 31050 ± 1500BP. Although the youngest two dates, from near the surface of the tufa, had been rejected as being anomalously young, the older dates were regarded as indicating tufa formation during the last cold stage. Biostratigraphic analyses of the molluscan and ostracod faunas, presented here, demonstrate that the tufa formed under fully temperate conditions throughout. The occurrence of certain snails that are either locally extinct (e.g. Belgrandia marginata) or unknown living in western France (e.g. Daudebardia brevipes), together with the geomorphological setting, suggest that the tufa is of interglacial age. New radiocarbon determinations of the Condat tufa all proved to be >33 Ka BP and support this conclusion.  相似文献   

东海浮游介形类生态适应分析   总被引：2，自引：0，他引：2  

徐兆礼 《海洋学报》2007,29(5):123-131

根据1997~2000年东海23°30'~33°N,118°30'~128°E海域4个季节海洋调查资料,用浮游介形类物种丰度和同步表层温、盐度数据进行曲线拟合,构造数学模型,计算介形类分布最适温度和盐度值,并参考其地理分布和生态适应特征分析,确定东海浮游介形类主要物种的生态类型.结果表明:在浮游介形类优势种中,后圆真浮萤(Euconchoecia maimai)、短棒真浮萤(E.Chierchiae)、针刺真浮萤(E.aculeata)、细长真浮萤(E.elongata)和齿形海萤(Cypridina dentata)等为亚热带外海种.这些种具有广泛的分布,如果冬、春季在较低水温出现,与东海北部外海暖流带入有密切的关系.腹突拟浮萤(Paraconchoecia decipiens)、猬刺拟浮萤(P.echinata)、棘刺拟浮莹(P.spinifera)、长拟浮萤(P.oblonga)、大浮萤(Conchoecia magna)和葱萤(Porroecia porrecta)等是热带大洋种,这些种主要分布在黑潮暖流、台湾暖流和台湾海峡水域.同心假浮萤(Pseudocon-choecia concentrica)和Paraconchoecia sp.最适温度较低,但地理分布特征显示前者是亚热带外海种,后者是暖温带外海种.所提到介形类其他物种最适盐度大多超过34,但最适温度在15~20℃之间.依据有关文献,这些种在我国从东海到南沙海域都有分布,分布虽广但数量稀少,难有证据表明这些种分布与暖流有密切的关系,是亚热带外海种.  相似文献   

Lateglacial and Holocene variation in aeolian sediment flux over the northeastern Tibetan Plateau recorded by laminated sediments of a saline meromictic lake   总被引：2，自引：0，他引：2  

Steffen Mischke  Chengjun Zhang  Anko Börner  Ulrike Herzschuh 《第四纪科学杂志》2010,25(2):162-177

Predominantly laminated lake sediments from a saline closed‐basin lake on the northeastern Tibetan Plateau were investigated using a multi‐proxy approach (¹⁴C‐accelerator mass spectrometry dating, smear‐slide analysis, loss on ignition, grain size, X‐ray diffraction, elemental concentration, ostracod assemblages, stable isotopes of ostracod shells) to trace the regional environmental and climatic history in the Lateglacial and Holocene. Before about 15 cal. ka BP, small saline water bodies probably filled the basin under unstable cold and harsh environmental conditions. Soon after about 14.9 cal. ka BP, a relatively deep saline lake was established, probably as a result of runoff from melting snow, ice and frozen ground in the lake's catchment. Large changes in flux of aeolian material to the lake were recorded during this initial period of formation of Lake Kuhai. Highest lake levels, a low sediment accumulation rate and less saline conditions were maintained between about 12.8 and 7.1 cal. ka BP when the aeolian influx diminished significantly. After about 7.1 cal. ka BP, the aeolian influx remained at a moderate level apart from a strongly increased dust delivery to the lake between about 6.1 and 5.4 cal. ka BP and a minor short‐lived period of slightly enhanced aeolian influx at about 2.7 cal. ka BP. The strongly enhanced dust input to the lake between 6.1 and 5.4 cal. ka BP represented the largest influx of aeolian material to Lake Kuhai during the entire Holocene. However, evidence for climatic deterioration during this period is not seen at most other palaeoclimate sites on the Tibetan Plateau, but instead a significant increase in aridity has been recorded at numerous sites in the northern foreland of the Tibetan Plateau and on the Chinese Loess Plateau. The large dust input to Lake Kuhai between 6.1 and 5.4 cal. ka BP probably did not result from a severe climate deterioration on the Tibetan Plateau itself, but from the pronounced aridity in its northern and eastern foreland. In contrast, the increase in dust influx about 2.7 cal. ka BP seems to correspond to a brief warming spell recorded at other sites on the Tibetan Plateau too. A slight increase in lake level and decrease in salinity after about 0.6 cal. ka BP suggests a slightly higher effective moisture during the final lake stage, accompanied by a somewhat larger dust influx. This apparent contradiction possibly results from enhanced human activities on the northeastern Tibetan Plateau during the last 600 years. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

The recognition of mid-Cretaceous sea-level changes by means of Foraminifera     

M. B. Hart 《Cretaceous Research》1980,1(4):289-297

Detailed microfaunal investigations of the mid-Cretaceous (Albian-Santonian) successions of S. E. England have allowed the recognition of a major rise in sea level during the Cenomanian, that reached a maximum in the Early Turonian. The water depth model presented in this account has also been compared to successions from environments ranging from marginal marine, to open shelf, and finally deep ocean, in an attempt to confirm its validity.  相似文献   

A survey of the non-marine Cretaceous in China     

Chen Pei-ji 《Cretaceous Research》1983,4(2):123-143

A review of the stratigraphy of the continental Cretaceous sequences is given. Conchastracans, ostracods and charophytes have proved useful in biostratigraphy, with additional aid from pelecypods, gastropods, larger plant fossil and, locally, dinosaur remains.The continental Lower Cretaceous deposits are considered to fall into three domains: the Circum-Pacific, the Tethyan and the NW Chinese. The continental Upper Cretaceous sediments occur mainly in the three domains: NW Chinese, SE Chinese and NE Chinese.  相似文献   

A late Quaternary ostracod record from Wallywash Great Pond, a Jamaican marl lake     

Jonathan A. Holmes 《Journal of Paleolimnology》1998,19(2):115-128

Two assemblages typify the ostracod fauna of a 9.23 meter core taken from Wallywash Great Pond, a small perennial freshwater marl lake in Jamaica. The first, dominated by Cypretta brevisaepta, lived in deep water, similar to present-day conditions. The second, dominated by Candonopsis sp., reflects the existence of a shallower lake. The core has a basal date of c. 125 kaBP. Four inferred deep-water phases occurred in the period 125–93.5 kaBP with periods of inferred shallower water in between. The lake was dry between 93.5 kaBP and c. 10 kaBP as suggested by the absence of ostracods or fossils of other aquatic organisms. Ostracod faunal evidence indicates that there have been three highstands and two lowstands of the lake during the Holocene, although ostracods are not preserved in the organic mud and lignite that formed under swampy conditions as the basin filled at the start of the Holocene and during part of the two subsequent lowstands of the lake. A major hydrological perturbation, associated with the flooding of the nearby Black River catchment around 1.2 kaBP, caused an increase in the ostracod species diversity of the Great Pond, although this was relatively short lived and the lake attained a faunal composition similar to present around 1 kaBP. Major variations in ostracod assemblages in the core thus represent lake-level changes and accord well with previously-published interpretations of water depth based on lithofacies variation and stable oxygen isotope ratios in authigenic carbonates.  相似文献   

柴达木盆地全球末次冰期介形类动物群的演变   总被引：9，自引：0，他引：9       下载免费PDF全文

孙镇城  曹丽  张海泉  张永华  董宁  乔子真  孙乃达  袁秀君  路艳丽  张宏欣 《古地理学报》2003,5(3):365-377

晚更新世晚期，柴达木盆地达参1井井深46m以下的沉积物内，水生生物化石有很高的丰度和分异度。介形类为 Cyprideis torosa-Ilyocypris inermis组合，伴生有轮藻类、腹足类、双壳类、植物和鱼类等化石。井深46m~10m，为全球末次冰期盛冰阶（25ka~10ka B.P）沉积，当时气候极端干冷，出现干盐湖地质事件（playa），沉积物由湖相泥岩迅速演变为石盐层，生物化石罕见，几近绝迹。平均40m厚的石盐沉积遍及三湖(台吉乃尔湖、达布逊湖和霍布逊湖)地区，形成了该区天然气赖以保存的最后一道屏障-天然气藏的盖层。井深约10m以上，为全新世暖期或称现代间冰期沉积物，渐变为浅湖相泥岩和粉砂岩夹膏盐沉积。当时处于氧同位素阶段1，湖水盐度逐渐降低，水生生物丰度和分异度再度增高，介形类更替为半咸水-淡水介形类Candona neglecta-Candoniella lactea组合，伴生有丰富的轮藻、腹足类、双壳类等。直到现代，台吉乃尔湖、达布逊湖和霍布逊湖以南由于受昆仑山充足的淡水补给影响，水生生物丰富。三湖以北，远离主要淡水补给区，水体较咸，介形类则为典型的盐湖介形类Eucypris inflata所替代，膏盐沉积比三湖以南明显增多。  相似文献