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1.
笔者于西藏仲巴县塔惹增地区一带前人划分的一套早白垩世早期则弄群中发现了具有典型意义的、代表早白垩世晚期的Ampullina xainzaensis Yu,Ampullina cf. larteli Landerer,Tylostoma cf. brasilianus Maury,Pseudamaura cf. subfournaeti (Pcelincev),Gyrodes gaultiana Orbigny,Leviathania cf. gerassimovi(Pcelincev),Gymnentome cf. pizcuetana(Vilanova)等腹足类化石,以及较为丰富的中圆笠虫Mesorbitolina sp.和达克斯虫Daxia sp。表明在该区则弄群中至少有一部分以前没有被识别出的早白垩世晚期地层。通过岩石组合特征、基本层序、生物化石时代对比,将该套地层归属于捷嘎组。这一地层的确定为冈底斯带白垩系地层划分对比、地层格架建立提供了重要的依据,并丰富了该地层的古生物资料,且为中生代盆地的演化历史、古地理轮廓的确定提供了新的基础资料。 相似文献
2.
Mario N Tamburri James P Barry 《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(12):47
Many deep-sea animals derive part of their nutrition from rare and unpredictable food falls. However, traits that allow organisms inhabiting the sea floor to exploit carrion are poorly understood. We found in laboratory experiments that hagfish (Eptatretus stouti), gastropods (Neptunea amianta) and amphipods (Orchomene obtusus) survived extended periods of starvation, in some cases for more than a year. When exposed to odors emitted from carrion, most individuals of E. stouti and O. obtusus began searching for food within seconds, whereas none responded to the scent of the live prey. In contrast, the slow crawling N. amianta readily consumed carrion but showed no apparent response to any odor solutions tested. Because more motile animals exhibited lower thresholds for response to signal molecules, sensitivity to chemical cues appears related to species mobility. Hagfish were also found to defend carrion from some competitors by releasing slime when feeding. Though varying dramatically in size, morphology, locomotive ability, and phylogeny, these three species all possess traits well suited for a scavenging lifestyle. 相似文献
3.
Coastal sea-surface temperature (SST) and sea-surface salinity (SSS), including seasonality, in northwest (NW) Europe during the early phase of the Eemian interglacial ca. 125 ka ago were reconstructed from Littorina littorea (common periwinkle) gastropods. The results were based on intra-annual δ18O analyses in recent and fossil shells, mainly originating from the sea of Kattegat (Sweden) and the English Channel (United Kingdom), and confined to intertidal settings. The Eemian L. littorea shells indicated annual SSTs in the range 8–18°C for the English Channel and 8–26°C for Kattegat. All specimens from the Eemian sites experienced summer SSTs of ca. 1–3°C above recent conditions. The estimated winter SST in the English Channel during the Eemian was comparable to modern measurements of ca. 8°C. However, the Kattegat region displayed Eemian winter SST approximately 8°C warmer than today, and similar to conditions in the western English Channel. The recent-fossil isotope analogue approach indicated high SSS above 35 practical salinity units (psu) for a channel south of England in full contact with the North Atlantic Ocean during the last interglacial. In addition, the Kattegat shells indicated a SSS of ca. 29 psu, which points out a North Sea affinity for this region during the Eemian. 相似文献
4.
The effects of Cu, Cd, Zn and Cr on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus were compared. The 96-h LC50 for Cu, Cd, Zn and Cr were 0.36, 1.52, 1.76 and 36.9 mg l−1, respectively. Four sublethal concentrations of each metal plus a control were prepared and the snails were exposed to experimental solutions for 96 h. Feeding behaviour was studied after the snails were starved for five days. As compared with the control, the number of individuals feeding was significantly reduced by exposure to 0.05 mg l−1 Cu, 0.2 mg l−1 Zn, 0.5 mg l−1 Cd and 5 mg l−1 Cr. The time spent feeding was greater for individuals exposed to greater concentrations of Zn and Cd but no effect was found for Cu and Cr. Chemoreception of food was studied by placing the snails at a fixed distance of 15 cm from the bait. The success rate of reaching the bait was less for individuals exposed to Cr but no effect was found for Zn, Cu or Cd. The time required for an individual to reach the bait decreased as the concentration of Zn increased. In contrast, a longer time was required for individuals exposed to Cr whereas the effect of Cd and Cu was insignificant. The potential of using feeding behaviour and chemoreception in contaminant evaluations is discussed. 相似文献
5.
Stable isotope fractionation between mollusc shells and marine waters from Martinique Island 总被引：1，自引：0，他引：1
Forty-nine aragonitic and calcitic shells from 14 species of marine tropical molluscs (Bivalvia, Gastropoda, Polyplacophora) and ambient waters from Martinique have been analyzed for their carbon and oxygen isotope compositions. Mineralogy of shells was systematically determined by Raman spectroscopy that reveals composite shell structures and early processes of diagenetic alteration. In mangrove, brackish waters result from the mixing between 89±1% of seawater and 11±1% of freshwater, a hydrological budget quantified by both oxygen isotope and salinity mass balance calculations. Mollusc shells from the mangrove environment (S=31‰; δ18O=0.5‰) are characterized by mean δ13C values (−1.2‰) lower than those (+2.6‰) living in the open sea (S=35‰; δ18O=1‰). These low carbon isotope compositions result from the oxidation of organic matter into bicarbonate ions used in the building of mollusc shells. The oxygen isotope compositions of the studied mollusc species are mainly controlled by the temperature and composition of seawater whereas the role of the so-called “vital effects” is negligible. Contrasting with carbon isotopes, variability in the δ18O values among and within species of mollusc shells is very low (1σ=0.15) for a given littoral environment. Using ambient temperatures of seawater (28-30 °C), oxygen isotope fractionations between all studied living species and environmental waters match those extrapolated from the fractionation equation established for molluscs by Grossman and Ku [Chem. Geol., Isot. Geosci. Sect. 59 (1986) 59] in the range 3-20 °C. By analyzing calcite and aragonite layers from the same shell or by comparing shells from different species living in the same environment, there is no evidence that oxygen isotope fractionation between aragonite and water differs from that between calcite and water. On the basis of these results, we conclude that the oxygen isotope compositions of shells from most fossil mollusc species are suitable to estimate past seawater temperatures at any paleolatitude. 相似文献
6.
渭河地区位于我国中部,包括甘肃、宁夏及陕西部分地区,新生代化石资料丰富.口盖作为我国陆相地层中广泛分布且类型丰富的化石,目前多报道于20世纪七、八十年代,主要见于奥陶纪、白垩纪-古近纪地层,且主要分布于我国东南部地区,西部仅在西藏有所见及.随着近些年渭河地区工作的不断进展,在渭南沈河张家坡剖面发现大量口盖化石,主要产于上新统游河组下部地层,岩性以灰绿色、青灰色砂质泥岩及砂岩为主.由于岩性疏松、成岩作用弱,通过清水浸泡、80目筛子淘洗、筛选及稀盐酸处理,对比早期研究成果,根据其形态结构特征,鉴定出4属12种(Mirolaminatus,Assiminea,Parafossarulus和Pseudemmericia),其中包括8个新种,均为上新世地层中首次发现的腹足类口盖化石.简单归纳了口盖化石演化序列,指出腹足类口盖化石的大小及厚度不能作为口盖化石演化特征,且钙化的比角质的更进步.该化石的发现为腹足类动物群、上新统口盖化石研究及古环境恢复提供了新的证据. 相似文献
7.
During surveillance on the toxicity of invertebrates such as bivalves inhabiting the coasts of Hiroshima Bay in 2001 and 2002, the carnivorous gastropod rapa whelk Rapana venosa collected in the estuary of Nikoh River, was found to contain toxins which showed paralytic actions in mice; the maximum toxicities (as paralytic shellfish poison, PSP) were 4.2 MU/g (May 2001) and 11.4 MU/g (April 2002). Their total toxicities were 224 and 206 MU/viscera of one specimen throughout the monitoring period. Attempts were made to identify the toxic principle in the gastropod. The viscera were extracted with 80% ethanol acidified with acetic acid, followed by defatting with dichloromethane. The aqueous layer obtained was treated with activated charcoal and then applied to a Sep-Pak C18 cartridge. The unbound toxic fraction was analyzed by high-performance liquid chromatography techniques. The gastropod toxin was rather unexpectedly identified as PSP. It was comprised of high toxic component (gonyautoxin-3; GTX3, GTX2, saxitoxin; STX) as the major components, which accounted for approximately 91 mol% of all components along with C1 and C2, which are N-sulfocarbamoyl derivatives. Judging from their toxin patterns, it is suggested that the PSP toxification mechanism of the gastropod that PSP toxins produced by phytoplankton such as Alexandrium tamarense, are transferred to and accumulated in plankton feeders such as the short-necked clam, and then transferred to this carnivorous rapa whelk R. venosa through predation. 相似文献
8.
Effects of heavy metals on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus (Powys) 总被引：1，自引：0，他引：1
The effects of Cu, Cd, Zn and Cr on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus were compared. The 96-h LC50 for Cu, Cd, Zn and Cr were 0.36, 1.52, 1.76 and 36.9 mg l−1, respectively. Four sublethal concentrations of each metal plus a control were prepared and the snails were exposed to experimental solutions for 96 h. Feeding behaviour was studied after the snails were starved for five days. As compared with the control, the number of individuals feeding was significantly reduced by exposure to 0.05 mg l−1 Cu, 0.2 mg l−1 Zn, 0.5 mg l−1 Cd and 5 mg l−1 Cr. The time spent feeding was greater for individuals exposed to greater concentrations of Zn and Cd but no effect was found for Cu and Cr. Chemoreception of food was studied by placing the snails at a fixed distance of 15 cm from the bait. The success rate of reaching the bait was less for individuals exposed to Cr but no effect was found for Zn, Cu or Cd. The time required for an individual to reach the bait decreased as the concentration of Zn increased. In contrast, a longer time was required for individuals exposed to Cr whereas the effect of Cd and Cu was insignificant. The potential of using feeding behaviour and chemoreception in contaminant evaluations is discussed. 相似文献
9.
腹足类口盖化石在我国中、新生代陆相地层中分布广泛，丰富而且类型多，但目前还没有系统的口盖化石分类，作者将它们按动物分类学的方法建立口盖化石分类系统，便于对口盖化石进行比较研究和鉴别。 相似文献
10.