Phosphatized embryo fossils from the Cambrian explosion

The earliest Cambrian (Meishucunian) phosphatized metazoanOlivooides from the Yangtze platform is represented by dierent developmental stages: from blastula through possible gastrula to tissue differentiation and finally to the hatched animals. The fossilization of embryos opens a new field in palaeontologypalaeoembryology. Embryological studies will be of importance for the understanding of ontogeny and phylogeny of metazoans from the Cambrian explosion.     

The internal structure of Early Cambrian fossil embryo <Emphasis Type="Italic">Olivooides</Emphasis> revealed in the light of Synchrotron X-ray Tomographic Microscopy

Countless fossil embryo Olivooides and the hatched larvae, juveniles and adults （the latter two kinds are Punctatus） are recovered by means of acid maceration from the fine-crystalline to medium-crystalline phosphatic limestone and phosphatic micrite of Early Cambrian Kuanchuanpu Formation at the Shizhonggou section, near Kuanchuanpu Village, Ningqiang County, Shaanxi Province, China. Using the technique of Synchrotron X-ray Tomographic Microscopy, the 3D internal structure of Ofivooides and Punctatus is reconstructed. The morphological and statistic analyses are also given to the stellae structure of Ofivooides and Punctatus, which indicates that this structure is a result of adaptive evolution to a lifestyle of fast-attaching after hatching, probably with the function of mucilage secretion. The internal structure of Punctatus is described and discussed. The ovum-like structure, a common internal feature of Punctatus, is considered as the taphonomic structure, rather than eggs or other biological structure. This structure is thought to be formed after the burial of the animal and before or during the mineralization. The original internal structure of Punctatus is assumed to be tabulae-filled, with soft body grown on them.     

河川沙塘鳢孵化腺的超微结构

为进一步了解河川沙塘鳢（Odontobutis potamophila）胚胎早期发育过程中孵化腺（Hatching gland,HG）的发生及其超微结构,采用透射电镜观察了河川沙塘鳢胚胎早期发育过程中心跳期、眼晶体形成期、血液循环期、眼黑色素出现期、孵化前期、初孵仔鱼期等6个不同时期的孵化腺超微结构。观察结果显示,河川沙塘鳢的孵化腺为单细胞腺体,最早可在眼晶体形成期观察到孵化腺细胞（Hatching glandc ells,HGCs）,主要分布于头部腹面、头部与卵黄囊连接处及其卵黄囊前腹面;当胚胎发育至血液循环期时,HGCs不仅在形态上达到最大,数量上急剧增多,而且分布更广泛;胚胎发育进入眼黑色素出现期时,可以观察到处于不同合成时期的酶原颗粒,每个酶原颗粒外面均有膜包围,颗粒之间有明显的界限;当胚胎发育至孵化前期时,HGCs在数量上达到最多,并且可以观察到呈圆球形、直径约为0．25—1．00μm的孵化酶颗粒自HGCs顶部的开口向外分泌,这些颗粒有的以单体形式存在,有些则粘结成团;初孵仔鱼期,HGCs分泌作用已经完成,它们离开胚胎表面,移至表皮细胞下方并逐渐衰退。以上结果表明,河川沙塘鳢孵化酶颗粒有一个成熟过程,成熟的孵化酶颗粒主要通过外倾方式向卵周隙中分泌以帮助胚胎的孵化破膜。     

In situ stable isotopic constraints on dolomitizing fluids for the hydrothermally-originated saddle dolomites at Keping, Tarim Basin

Detailed characterization of diagenetic fluid behaviour and evolution is commonly hindered by shortage of appropriate and economic methods to carry out in situ analysis in the tiny diagenetic mineral crystals. Using micromill sampling method, this study presents in situ stable isotopic data for the growth zones of saddle dolomite crystals in the hydrothermally-altered dolostones of Upper Cambrian (Furongian) at Keping, Tarim Basin, NW China. These data show minor and large variations in δ13C ( 0.7‰ to 1.5‰ VPDB) and δ18O ( 8.3‰ to 13.8‰ VPDB), respectively, from the cores to outer rims of the dolomite crystals and suggest that saddle dolomites precipitated from dolomitizing fluids with similar carbon sources but oscillatory temperatures during different formation stages. This scenario is confirmed by microthermometry of fluid inclusions within the growth zones of dolomite crystals. This study indicates that in situ isotope analysis could provide more detailed information related to the source and pathway of dolomitizing fluids, facilitating better characterization of dolomitizing fluids and processes.     

Developmental sequence of Cambrian embryo Markuelia

Based on more exquisitely preserved specimens of Markuelia hunanensis recently recovered from Middle and Upper Cambrian in western Hunan and in the light of Synchrotron radiation X-ray tomo-graphic microscopy, the developmental sequence from cleavage through organogenesis to the pre-hatching of Cambrian embryo Markuelia, especially the developmental sequence during the pre-hatching stage, i.e. from the earliest period when the scalids and tail spines only took shape to the latest period (just about hatching), is established. This developmental sequence provides a pattern of embryonic development during the pre-hatching stage, which has not been established in the living scalidophorans (priapulids, loriciferans and kinorhynchs). Thus, it not only enriches our knowledge on the embryonic development of the extant descendants of Markuelia, but also opens a new window to the evolution and development of the animal.     

New anomalocardid frontal appendages from the Guanshan biota, eastern Yunnan

Anomalocaridids were large predators of the Cambrian seas at the top of the trophic pyramid. Complete anomalocaridid specimens have been rarely discovered and the rigid isolated frontal appendages and mouthparts are more commonly preserved. Here we study new material of the frontal appendages from the Wulongqing Formation, Cambrian Stage 4, Series 2 near Kunming, eastern Yunnan. Two new forms of anomalocaridid frontal appendages are described, namely Anomalocaris kunmingensis sp. nov. and Paranomalocaris multisegmentalis gen. nov., sp. nov. The frontal appendage of A. kunmingensis sp. nov. probably comprises 15 podomeres of which the first one has a weakened skeletoned, the second one is armed with small spines, and the third one is armed with remarkably robust proximal ventral spines with 6 anisomerous auxiliary spines; paired auxiliary spines are associated with podomeres 4–14; podomeres 12–14 are armed with paired dorsal spines, and the last podomere bears 2 distal spines, one spine distinctly larger than the other. The frontal appendage of P. multisegmentalis tapered backwards, consisting of 22 visible podomeres; the most ventral spine is armed with 5 pairs of auxiliary spines, and podomeres 12–21 bear dorsal spines, the last podomere with 2 small distal spines. The new material provides additional evidence for our understanding of the diversity of anomalocaridids in the Cambrian. The morphology of these new finds may indicate the importance of different feeding strategies of anomalocaridids in the Cambrian ecosystem.     

Provincialism of the late Middle through middle Late Cambrian paraconodonts and protoconodonts

Quantitative paleoprovincialism is studied, using a coefficient of similarity (CS) formula. The results indicate that the provincialism of the late Middle through middle Late Cambrian paraconodonts and protoconodonts did exist. The provincialism of Ordovician conodonts can be traced back to late Middle Cambrian. The North China Province and South China Province can be recognized in late Middle Cambrian, whereas the North China Province, South China Province and Balitca Province can be recognized respectively in early Late Cambrian and middle Late Cambrian. The possibility that the larger units of provincialism, i.e. Faunal Regions existed in the areas mentioned above is discussed. It is inferred that the Midcontinent Faunal Region and the Atlantic Faunal Region had existed in early Late Cambrian and middle Late Cambrian. The North China Province was the secondary unit of provincialism in the Midcontinent Faunal Region, while the Baltica Province was that in the Atlantic Faunal Region. The South China Province is the secondary unit of provincialism between the two largest units of provincialism. Moreover, the comparison with the trilobite provincialism which has been accumulated on a solid basis of research is made, and the paleogeographic positions of North China Massif, South China Massif and Tarim Massif are revised.     

Detrital zircon of 4.1 Ga in South China

One hadean zircon from the Cambrian sandstone in the southern part of South China has a U-Pb age of 4107±29 Ma with ε Hf(t) value similar to that of the homochronous depleted mantle and Hf model age of 4102±21 Ma.This demonstrates the existence of hadean crustal remnant in South China.A close match between the U-Pb age and Hf model age with the highly position ε Hf(t) value indicates the growth and immediate reworking of juvenile crust from the depleted mantle at ca 4.1 Ga.The prominent "Pan-African" and Grenville zircons derived from the exotic sources were also found in the sample,which indicates a linking between South China and Gondwana in the Cambrian period.The southern part of South China has complex histories of crustal growth and tectonic evolution.     

Flabellariopteris,a new aquatic fern leaf from the Late Triassic of western Liaoning,China

An aquatic fern leaf, Flabellariopteris mii Sun gen. et sp. nov. from the Late Triassic of Western Liaoning, China, is described and proposed as the type species of the new morphortaxon of the Marsileaceae. The fossil leaves are preserved as impression. No fertile and rhizomatic materials are found. The leaves attached at a common point on the top of the petiole are composed of two leaflets joined basally in an opposite arrangement. The petiole is slender. The leaflet is fan-shaped or semi-circular, and commonly divided into four wedge-shaped lobes. Terminal margin of lobes is usually incised, incisions shallow or deep, with bluntly rounded or notched apex. The veins are conspicu- ously dichotomous, but anastomoses and marginal vein are absent. The unique morphological features, including two- parted thin leaflets, size, shape, veins and slender petiole, indicate that the present specimen represents an aquatic fern, which is the oldest fossil record and the first megafossil evidence assignable to Marsileaceae from the Triassic floras.     

湘西花垣中寒武统具表面装饰的管状微体化石

对采自湘西花垣县排碧剖面中寒武统花桥组灰岩中具表面装饰的磷灰石质管状化石（Ornamented tubes）进行了研究,依据化石的壳面装饰特征,建立了3形态类型：Ornamented Tube Form Ⅰ,Ornamented Tube Form Ⅱ 和 Ornamented Tube Form Ⅲ。其中Ⅰ型壳体表面装饰有尖细的小刺,多数标本壳刺成行排列,行间存在宽约0.01～0.05 mm的间隔;Ⅱ 型管体表面具有零散稀疏而不规则分布的斑疹状壳饰,壳体微微向外弯曲的一侧具有一列粗壮的呈锯齿状排列的脊刺;Ⅲ型整个壳体表面布满圆形、卵圆形瘤状壳饰,壳饰中空,与壳体内腔相通,壳体微微向外弯曲的一侧具有一列粗壮的呈羽状排列的脊刺。从壳体形态、表面装饰特征分析,这类管状化石可能是节肢动物(如高肌虫类)生物体壳瓣上的前刺或背部的刺等管状硬体构造。     

A single stem cell can recolonize an embryonic thymus, producing phenotypically distinct T-cell populations

There is much interest in early T-cell development, particularly in relation to the diversification of the T-cell receptor repertoire and the elucidation of the lineage relationships between T-cell populations in the thymus and peripheral lymphoid organs. However, the requirements for the growth of the earliest thymic T-cell precursor in 13-14-day mouse embryo thymus in isolation from the thymic environment are unknown. Proliferation and maturation of such cells are not sustained either in the presence of monolayers of thymic stromal cells or by the addition of interleukin-2 (IL-2), despite the expression of receptors for this growth factor on a proportion of thymocytes displaying the immature Thy 1+ Lyt-2-L3T4- phenotype in the embryonic thymus. In contrast, when maintained within the intact thymic environment in organ cultures, 13-14-day thymic stem cells do show a pattern of surface marker and functional development similar to that seen in vivo, suggesting that short-range growth signals, perhaps necessitating direct contact with organized epithelial cells, are required. We have shown, by exploiting the selective toxicity of deoxyguanosine (dGuo) for early T cells, that this organ culture system can be manipulated to produce alymphoid lobes that can be recolonized from a source of precursors in a transfilter system. We now show that recolonization of alymphoid lobes can also be achieved by association with T-cell precursors in hanging drops, allowing recolonization by exposure to defined numbers of precursors, including a single micromanipulated stem cell. Analysis of T-cell marker expression in these cultures shows that a single thymic stem cell can produce progeny of distinct phenotypes, suggesting that these marker-defined populations are not derived from separate prethymic precursors, but arise within the thymus.     

Re-Os isotopes and PGE geochemistry of black shales and intercalated Ni-Mo polymetallic sulfide bed from the Lower Cambrian Niutitang Formation, South China

The paleo oceanenvironmentalchangeduringthePrecambrian Cambriantransitionisakeyissuere latedtothecausesforanexplosiveradiationofdiffer entmetazoanphyladuringtheEarlyCambrianera .Thechemicalandisotopiccompositionsofmarinesed iments (carbonates ,phosphorites ,siliceousrocks ,andblackshales)recordthechangingcompositionandphysicalconditionsoftheseawaterinwhichtheserocksaccumulated .Organiccarbon richblackshalesfrommarineenvironmentsarecommonlyenrichedinanumberoftraceelementssuchasNi,Mo ,V ,Co ,…     

中国林蛙胚胎后期发育观察

首次对中国林蛙在华南地区的胚胎后期发育进行观察研究.结果表明:华南地区的环境条件基本适合中国林蛙的胚胎后期发育,较高的温度加快了中国林蛙的胚胎发育进程,但对其生长无明显影响.     

DEX1, a plasma membrane-localized protein, functions in microspore development by affecting CalS5 expression in Arabidopsis thaliana

Microsporogenesis in flowering plants plays important roles in sexual reproduction. It has been reported that DEFECTIVE IN EXINE FORMATION1 (DEX1) is essential for exine pattern formation in Arabidopsis thaliana. However, the functions of DEX1 in regulating microspore development are largely not understood. In this study, we show that DEX1 is strongly expressed in the tapetum by using RNA in situ hybridization. dex1 microspores were degenerated and aborted after release from the tetrads. The callose wall in tetrads was thinner in the dex1 mutant than in the wild type, suggesting that DEX1 affects callose formation at the tetrad stage during anther development. RT-PCR and real-time PCR analyses showed that CalS5, which plays an important role in callose synthesis during microspore development, was greatly down-regulated in dex1 plants. DEX1 encodes a membrane protein with one transmembrane domain, one intracellular domain and one extracellular domain. Collectively, our results demonstrate that DEX1 is essential for microspore development, possibly by regulating the expression of CalS5.     

A giant Ordovician anomalocaridid

Anomalocaridids, giant lightly sclerotized invertebrate predators, occur in a number of exceptionally preserved early and middle Cambrian (542-501?million years ago) biotas and have come to symbolize the unfamiliar morphologies displayed by stem organisms in faunas of the Burgess Shale type. They are characterized by a pair of anterior, segmented appendages, a circlet of plates around the mouth, and an elongate segmented trunk lacking true tergites with a pair of flexible lateral lobes per segment. Disarticulated body parts, such as the anterior appendages and oral circlet, had been assigned to a range of taxonomic groups--but the discovery of complete specimens from the middle Cambrian Burgess Shale showed that these disparate elements all belong to a single kind of animal. Phylogenetic analyses support a position of anomalocaridids in the arthropod stem, as a sister group to the euarthropods. The anomalocaridids were the largest animals in Cambrian communities. The youngest unequivocal examples occur in the middle Cambrian Marjum Formation of Utah but an arthropod retaining some anomalocaridid characteristics is present in the Devonian of Germany. Here we report the post-Cambrian occurrence of anomalocaridids, from the Early Ordovician (488-472?million years ago) Fezouata Biota in southeastern Morocco, including specimens larger than any in Cambrian biotas. These giant animals were an important element of some marine communities for about 30?million years longer than previously realized. The Moroccan specimens confirm the presence of a dorsal array of flexible blades attached to a transverse rachis on the trunk segments; these blades probably functioned as gills.     

慈姑雌花在自然居群中的受粉过程--花粉粒落置、萌芽及花粉管生长的荧光显微观察

用荧光显微术观察了慈姑（Ｓａｇｉｔｔａｒｉａ ｔｒｉｆｏｌｉａ Ｌｉｎｎ）不同时期的雌花柱头上花粉粒的落置、萌发及花粉管的生长过程与途径。结果表明：该种雌花开花２ｈ 柱头受粉率为０,开花４ｈ 和８ｈ受粉率分别为５３８％ 和９８３％ ,柱头上花粉萌发率达１００％ ;花粉管沿雌蕊之向心一侧的组织中穿行,至子房基部后部分花粉管转向胚珠,由珠孔进入珠心。本研究发现该种花粉管常穿过子房基部至花托组织,并可进入其他雌蕊中,作者认为这种行为可能对保证雌花的结实率有一定意义     

Scriptaid affects histone acetylation and the expression of development-related genes at different stages of porcine somatic cell nuclear transfer embryo during early development

Although the somatic cell nuclear transfer(SCNT) technique has been used extensively for cloning and generating transgenic pigs,the cloning efficiency is still very low.It has been proposed that the low efficiency of this technique is the result of incomplete epigenetic reprogramming and abnormal gene expression during early embryonic development.In this study,we investigate the effect of Scriptaid,a low-toxicity histone deacetylase inhibitor,on the developmental competence of porcine SCNT embryos.We found that treating SCNT embryos with 500 nmol/L Scriptaid for 15 h after activation significantly enhanced the blastocyst formation rate(27.7%) compared with the untreated group(control)(12.2%,P<0.05).Using an immunofluorescence technique to measure the average fluorescence intensity,we also found that treating SCNT embryos with Scriptaid increased the level of histone acetylation on histone H3 at lysine 14(acH3K14).Furthermore,treating embryos with Scriptaid increased the expression level of three genes that play important roles during embryonic development(Oct4,Klf4 at the blastocyst stage and Nanog at the 4-cell stage).Moreover,the expression level of the apoptosis-related gene Caspase-3 was significantly lower in the Scriptaid-treated SCNT embryos compared with the control SCNT embryos at the 4-cell and blastocyst stages.In conclusion,these results indicate that Scriptaid treatment improves the development and nuclear reprogramming of porcine SCNT embryos.     

A restudy of Oryctocephalus indicus (Reed, 1910)

Restudy on morphology of Oryctocephalus indicus (Reed, 1910), based on specimens from Guizhou, China and Nevada USA, suggests that the subspecies regarded previously as Oryctocephalus indicus indicus (Reed, 1910), O. indicus latus Zhao et Yuan 2002, and O. indicus kobayashi Saito, 1934, are synonymous, and Oryctocephalus americanus Sundberg et McCollum, 2003 is a similar form of O. indicus. Oryctocephalus indicus is rediagnosed as having a glabella that is subconical in outline and tapering forward slightly; a thorax that comprises 12 segments, and a small pygidium that bears 2?3 axial rings with a terminal piece and a postaxial ridge. Oryctocephalus indicus is widely distributed in eastern Guizhou and ranges through a great interval of Kaili Formation. Its first appearance is almost identical with these events of trilobite extinction-recovery occurring at the end of the Early Cambrian, the alternation of acritach assemblages, the change of trace elements (REE) and stable isotopes (carbon) at the Wuliu-Zengjiaya section. As one of the key forms for defining the traditional Lower - Middle Cambrian boundary (the base of Cambrian Series 3 and Stage 5 in the new Cambrian chronstratigraphic standard), O. indicus has received detailed study and has more advantages than other species such as Ovatoryctocara granulata Tchernysheva, 1962 or Arthricocephalus chauveaui Bergeron, 1899.     

Opening of the Longmu Co–Shuanghu–Lancangjiang ocean:constraints from plagiogranites

This paper reports new zircon U-Pb ages,and Hf isotope and whole-rock major and trace element data for Cambrian plagiogranites from the Tuobeiling ophiolite in central Qiangtang,Tibetan Plateau.Zircon SIMS and LAICP-MS U-Pb dating of the plagiogranites yield weighted mean ages of 504.8±4.2 and 491.6±1.5 Ma,respectively.The zircons from plagiogranites exhibit positive eHf(t)values(ranging from 11.46 to 15.16),indicating that the plagiogranites are derived from depleted mantle.These plagiogranites are characterized by high SiO2and Na2O,low K2O,low REE contents,and flat REE distribution patterns.These rocks have geochemical compositions typical of oceanic plagiogranite and,considered along with their petrography and field relationships,are interpreted to have derived from anatexis of hydrated amphibolites by ductile shearing during transports of the oceanic crust.The formation age of such type of plagiogranite is slightly younger than that of the associated section of oceanic crust.Thus the new results from these plagiogranites suggest that the Longmu Co–Shuanghu–Lancangjiang ocean had probably opened before the Middle Cambrian.