中国和其他全北界三趾马的头骨和头后骨骼形态比较(英文)

由于地理位置上处于北美和旧大陆西部之间,中国晚中新世的三趾马提供了重要的生物地层与生物地理信息。这些信息反映出晚中新世时期北美和欧亚大陆之间的动物群交流,同时也与当时的古环境变迁相关联。依据面部和牙齿形态以及肢骨比例,将中国的三趾马与欧亚大陆及北美的其他种类进行了对比。中国的三趾马可识别出两个分类类群,其中一个非系统发育意义上的类群包括 Hipparion dermatorhinum,H. weihoense,H. fossatum,H. hippidio-dus 和 H. coelophyes,这一类群与旧大陆西部的三趾马在形态上高度相似; 另一个为本土类群,包括 H. ptychodus,H. platyodus,H. tylodus,H. sefvei 和 H. plocodus,它们与其他地区的种类并无相似之处。前一个类群是中国北方草原型动物群中的典型分子,对欧亚大陆化石地点的生物地层对比相当重要; 后一类群与北美的三趾马( "Cormohipparion"属) 在面部形态上具有相似性,这些本土的三趾马是中国北方森林型动物群的分子。     

Bombyx acid cysteine proteinase

Summary

Three kinds of yolk proteins (vitellin, egg-specific protein and 30 k-proteins) are found in silkmoth eggs and have been well characterized. Essentially these proteins are considered to be amino acid reserves for developing embryos. Since at an early stage of egg development the cysteine proteinase accounts for the majority of the total proteinase activity, it may be involved in the degradation of yolk proteins. The enzyme is stored in the eggs as an inactive pro-form, indicating that the activation of the enzyme might be one of the key steps in yolk protein degradation. To investigate at the molecular level how yolk proteins degradation takes place, we have studied Bombyx acid cysteine proteinase (BCP) during an early period of embryonic development. We summarize how proteinases are regulated and are involved in the degradation of Bombyx yolk proteins during embryogenesis. These will be discussed mainly in light of recent results obtained from eggs of the silkmoth, Bombyx mori.     

Drosophila subpulchrella, a new species of the Drosophila suzukii species subgroup from Japan and China (Diptera: Drosophilidae)

Drosophila (Sophophora) subpulchrella Takamori and Watabe, sp. nov., of the D. suzukii subgroup in the D. melanogaster species group, is described from Japan and southern China, and compared with its sibling species, D. pulchrella Tan et al. distributed in the Yun‐Gui Highland, south‐western China. The results of cross‐experiments show a complete pre‐mating isolation between D. subpulchrella and D. pulchrella.     

Ontogenetic histology of Stegosaurus plates and spikes

Abstract: The dinosaur Stegosaurus is characterized by osteoderms of alternating plates and terminal paired spikes. Previous studies have described the histological features and possible functions of these osteoderms. However, ontogenetic changes are poorly documented. In this study, the ontogenetic changes of the osteoderms are examined using eight different ontogenetic skeletons (a juvenile, a subadult, a young adult, and five old adults based on the cortical histology of their body skeletons). The juvenile plate and subadult spike show thin cortex and thick cancellous bone. The young adult plates have an extensive vascular network, which is also seen in old adults. Old adult spikes are different from old adult plates in having a thick cortex and a large axial channel. The cortical histology, in both plates and spikes, show well‐vascularized bone tissue consisting of dense mineralized fibres in young adult forms. In old adult forms, the bone tissues in the spikes become more compact and are extensively remodelled. This might contribute to the structural reinforcement of the spikes. The plates in old adult forms also show extensive remodelling and lines of arrested growth, but only limited signs of compaction. The timing for acquisition of features seen in old adults is different between plates (an extensive vascular network in the young adult) and spikes (a thick cortex with a large axial channel in old adults). The result suggests that the timing for plate and spike functions is different. The extensive vascular networks seen in large plates suggest their function is for display and/or thermoregulation. The thick cortical bone of spikes of old adults suggests that spikes acquire a weapon function for defence ontogenetically late.     

Neural population representation hypothesis of visual flow and its illusory after effect in the brain: psychophysics,neurophysiology and computational approaches

The neural representation of motion aftereffects induced by various visual flows (translational, rotational, motion-in-depth, and translational transparent flows) was studied under the hypothesis that the imbalances in discharge activities would occur in favor in the direction opposite to the adapting stimulation in the monkey MST cells (cells in the medial superior temporal area) which can discriminate the mode (i.e., translational, rotational, or motion-in-depth) of the given flow. In single-unit recording experiments conducted on anaesthetized monkeys, we found that the rate of spontaneous discharge and the sensitivity to a test stimulus moving in the preferred direction decreased after receiving an adapting stimulation moving in the preferred direction, whereas they increased after receiving an adapting stimulation moving in the null direction. To consistently explain the bidirectional perception of a transparent visual flow and its unidirectional motion aftereffect by the same hypothesis, we need to assume the existence of two subtypes of MST D cells which show directionally selective responses to a translational flow: component cells and integration cells. Our physiological investigation revealed that the MST D cells could be divided into two types: one responded to a transparent flow by two peaks at the instances when the direction of one of the component flow matched the preferred direction of the cell, and the other responded by a single peak at the instance when the direction of the integrated motion matched the preferred direction. In psychophysical experiments on human subjects, we found evidence for the existence of component and integration representations in the human brain. To explain the different motion perceptions, i.e., two transparent flows during presentation of the flows and a single flow in the opposite direction to the integrated flows after stopping the flow stimuli, we suggest that the pattern-discrimination system can select the motion representation that is consistent with the perception of the pattern from two motion representations. We discuss the computational aspects related to the integration of component motion fields.     

A Japanese patient with the Costello syndrome

The Costello syndrome is characterized by dwarfism, unique cutaneous lesions, distinct facial gestalt, and mental retardation. We present a Japanese patient with the Costello syndrome. She showed high serum IgM level during the early infantile period. Nissen's fundplication was carried out to treat severe gastroesophageal reflux. Endocrinological investigations revealed a partial deficiency of growth hormone.     

Phosphatic Shell Formation in Atremate Brachiopods

The atremate brachiopods are unique in that they possess shellsof calcium phosphate. In Lingula adamsi and Gloltidia pyramidata,the shell mineral is (CO₃ + F)-containing apatite and is crystallo-chemicallysimilar but not identical to the mineral francolite. The shellof Glottidia consists of a thin periostracum, a mineralizedthick primary layer, and alternating mineralized layers andless mineralized chitin layers. The basic unit of the crystalsis the spherulite. Proteinaceous and glycosaminoglycan (GAG)matrices are present in the primary and mineralized layers.The GAGS in the chitin layer are morphologically different fromthose of the other layers. The GAGS are intimately associatedwith the apatite crystals. Shell formation appears to be mediated by three different typesof cells in the outer epithelium. The cells primarily involvedin the mineral formation are characterized by many vacuoleswith electron-dense granular inclusions containing Ca, P, andS. The connective tissue at the anterior edge of the mantlealso contains fine granules with Ca, P, and S. Those granulesare considered to be a mineral reserve for shell formation.Some problems of the mechanisms of shell formation are discussed.     

Studies on shell formation. VIII. Electron microscopy of crystal growth of the nacreous layer of the oyster Crassostrea virginica

Electron microscope observations have been made by means of the replica method on growth processes of calcite crystals of the nacreous layer of the shell of the oyster, Crassostrea virginica. Layer formation is initiated by the secretion of a conchiolin matrix and the deposition of rounded crystal seeds on or in this material. In some areas crystal seeds are elongate and within a given area show a similar orientation, probably due to slower deposition. The seeds appear to increase in size by dendritic growth, and smaller seeds become incorporated into larger ones which come into contact to form a single layer. With further growth, crystals overlap, forming a step-like arrangement. The direction of growth is frequently different in neighboring regions. Crystal seeds deposited on crystal surfaces are usually elongate and oriented. Well developed crystals have a tabular idiomorphic form and are parallel in their growth. Rounded and irregular crystals were also observed. The crystals show reticular structure with units of the order of 100 A and striations corresponding with the rhombohedral axes of the crystals. The role of the mantle is discussed in relation to the growth patterns of crystals and shell structure.     

蒙古戈壁上白垩统的暴龙类额骨(英文)

记述了发现于蒙古戈壁查干泰格地点的一块额骨。短的眶缘和矢状脊的存在等特征表明,该标本属于暴龙超科。查干泰格地点出露的地层被认为属于森诺曼-桑托期的巴音沙拉组,新材料的发现为上白垩统下部非常稀少的暴龙类恐龙记录增添了新的内容。     

Molecular phylogeny of the <Emphasis Type="Italic">Drosophila obscura</Emphasis> species group,with emphasis on the Old World species

Background  

Species of the Drosophila obscura species group (e.g., D. pseudoobscura, D. subobscura) have served as favorable models in evolutionary studies since the 1930's. Despite numbers of studies conducted with varied types of data, the basal phylogeny in this group is still controversial, presumably owing to not only the hypothetical 'rapid radiation' history of this group, but also limited taxon sampling from the Old World (esp. the Oriental and Afrotropical regions). Here we reconstruct the phylogeny of this group by using sequence data from 6 loci of 21 species (including 16 Old World ones) covering all the 6 subgroups of this group, estimate the divergence times among lineages, and statistically test the 'rapid radiation' hypothesis.