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1.
On the origin of the Hirudinea and the demise of the Oligochaeta 总被引:10,自引:0,他引:10
Martin P 《Proceedings. Biological sciences / The Royal Society》2001,268(1471):1089-1098
The phylogenetic relationships of the Clitellata were investigated with a data set of published and new complete 18S rRNA gene sequences of 51 species representing 41 families. Sequences were aligned on the basis of a secondary structure model and analysed with maximum parsimony and maximum likelihood. In contrast to the latter method, parsimony did not recover the monophyly of Clitellata. However, a close scrutiny of the data suggested a spurious attraction between some polychaetes and clitellates. As a rule, molecular trees are closely aligned with morphology-based phylogenies. Acanthobdellida and Euhirudinea were reconciled in their traditional Hirudinea clade and were included in the Oligochaeta with the Branchiobdellida via the Lumbriculidae as a possible link between the two assemblages. While the 18S gene yielded a meaningful historical signal for determining relationships within clitellates, the exact position of Hirudinea and Branchiobdellida within oligochaetes remained unresolved. The lack of phylogenetic signal is interpreted as evidence for a rapid radiation of these taxa. The placement of Clitellata within the Polychaeta remained unresolved. The biological reality of polytomies within annelids is suggested and supports the hypothesis of an extremely ancient radiation of polychaetes and emergence of clitellates. 相似文献
2.
Göran Malmberg 《Systematic parasitology》1990,17(1):1-65
Data on the ontogeny of the posterior haptor of monogeneans were obtained from more than 150 publications and summarised. These data were plotted into diagrams showing evolutionary capacity levels based on the theory of a progressive evolution of marginal hooks, anchors and other attachment components of the posterior haptor in the Monogenea (Malmberg, 1986). 5 + 5 unhinged marginal hooks are assumed to be the most primitive monogenean haptoral condition. Thus the diagrams were founded on a 5 + 5 unhinged marginal hook evolutionary capacity level, and the evolutionary capacity levels of anchors and other haptoral attachement components were arranged according to haptoral ontogenetical sequences. In the final plotting diagram data on hosts, type of spermatozoa, oncomiracidial ciliation, sensilla pattern and protonephridial systems were also included. In this way a number of correlations were revealed. Thus, for example, the number of 5 + 5 marginal hooks correlates with the most primitive monogenean type of spermatozoon and with few sensillae, many ciliated cells and a simple protonephridial system in the oncomiracidium. On the basis of the reviewed data it is concluded that the ancient monogeneans with 5 + 5 unhinged marginal hooks were divided into two main lines, one retaining unhinged marginal hooks and the other evolving hinged marginal hooks. Both main lines have recent representatives at different marginal hook evolutionary capacity levels, i.e. monogeneans retaining a haptor with only marginal hooks. For the main line with hinged marginal hooks the name Articulon-choinea n. subclass is proposed. Members with 8 + 8 hinged marginal hooks only are here called Proanchorea n. superord. Monogeneans with unhinged marginal hooks only are here called Ananchorea n. superord. and three new families are erected for its recent members: Anonchohapteridae n. fam., Acolpentronidae n. fam. and Anacanthoridae n. fam. (with 7 + 7, 8 + 8 and 9 + 9 unhinged marginal hooks, respectively). Except for the families of Articulonchoinea (e.g. Acanthocotylidae, Gyrodactylidae, Tetraonchoididae) Bychowsky's (1957) division of the Monogenea into the Oligonchoinea and Polyonchoinea fits the proposed scheme, i.e. monogeneans with unhinged marginal hooks form one old group, the Oligonchoinea, which have 5 + 5 unhinged marginal hooks, and the other group form the Polyonchoinea, which (with the exception of the Hexabothriidae) has a greater number (7 + 7, 8 + 8 or 9 + 9) of unhinged marginal hooks. It is proposed that both these names, Oligonchoinea (sensu mihi) and Polyonchoinea (sensu mihi), will be retained on one side and Articulonchoinea placed on the other side, which reflects the early monogenean evolution. Except for the members of Ananchorea [Polyonchoinea], all members of the Oligonchoinea and Polyonchoinea have anchors, which imply that they are further evolved, i.e. have passed the 5 + 5 marginal hook evolutionary capacity level (Malmberg, 1986). There are two main types of anchors in the Monogenea: haptoral anchors, with anlages appearing in the haptor, and peduncular anchors, with anlages in the peduncle. There are two types of haptoral anchors: peripheral haptoral anchors, ontogenetically the oldest, and central haptoral anchors. Peduncular anchors, in turn, are ontogenetically younger than peripheral haptoral anchors. There may be two pairs of peduncular anchors: medial peduncular anchors, ontogentically the oldest, and lateral peduncular anchors. Only peduncular (not haptoral) anchors have anchor bars. Monogeneans with haptoral anchors are here called Mediohaptanchorea n. superord. and Laterohaptanchorea n. superord. or haptanchoreans. All oligonchoineans and the oldest polyonchoineans are haptanchoreans. Certain members of Calceostomatidae [Polyonchoinea] are the only monogeneans with both (peripheral) haptoral and peduncular anchors (one pair). These monogeneans are here called Mixanchorea n. superord. Polyonchoineans with peduncular anchors and unhinged marginal hooks are here called the Pedunculanchorea n. superord. The most primitive pedunculanchoreans have only one pair of peduncular anchors with an anchor bar, while the most advanced have both medial and lateral peduncular anchors; each pair having an anchor bar. Certain families of the Articulonchoinea, the Anchorea n. superord., also have peduncular anchors (parallel evolution): only one family, the Sundanonchidae n. fam., has both medial and lateral peduncular anchors, each anchor pair with an anchor bar. Evolutionary lines from different monogenean evolutionary capacity levels are discussed and a new system of classification for the Monogenea is proposed.In agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. EditorIn agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. Editor 相似文献
3.
Zhou SQ 《Hereditas》2003,138(1):65-72
The aneuploidy of Gossypium hirsutum L. (upland cotton) aneusomatics were obtained by induced parthenogenesis. These aneuploids could grow and set seeds normally. In the process of meiosis there appeared large quantities of heteromorphic pairs and multivalent chromosomes and many cases of cytomixis and multisperm fertilization occurred. The aneuploids produced offsprings through sexual propagation. We explored penetratingly the questions how and why these aneuploids could survive. Through this research, we found that the upland cotton possessed an immense latent capacity to adapt to adverse environments. More importantly, in the case of the upland cotton, we discovered that the genetic pattern of the polyploid differs in some respects from that of the diploid. 相似文献
4.
Z M Drozdovski? 《Arkhiv anatomii, gistologii i émbriologii》1977,73(9):88-94
The figure of tetrahedron is formed in certain species of Plectus and in Tobrilus gracilis at the stage of 4 blastomeres rather than a rhombus which is formed in most highly organized nematodes. The analysis of the Nematoda's embryogenesis allows to conclude that tetrahedron, rhombus as well as some other figures play the role of preblastula sustaining the most expedient disposition of the first blastomers for transition to the formation of the blastula. With the increasing organization of nematodas the tetrahedron preblastula turns into a rhombic, linear-rhombic and at last in aphelenchoid-tylenchoid one. The character of the distribution of structural elements of organs and tissues of the definitive animal in the cytoplasm of the egg of Plectus and Tobrilus confirms the rightness of the division of the class of nematodas into subclasses Enoplia and Chromadoria rather than subclasses Adenophorea and Secernentea. 相似文献
5.
Ectogenesis, or the use of an artificial womb to allow a foetus to develop, will likely become a reality within a few decades, and could significantly affect the abortion debate. We first examine the implications for Judith Jarvis Thomson’s violinist analogy, which argues for a woman’s right to withdraw life support from the foetus and so terminate her pregnancy, even if the foetus is granted full moral status. We show that on Thomson’s reasoning, there is no right to the death of the foetus, and abortion is not permissible if ectogenesis is available, provided it is safe and inexpensive. This raises the question of whether there are persuasive reasons for the right to the death of the foetus that could be exercised in the context of ectogenesis. Eric Mathison and Jeremy Davis have examined several arguments for this right, doubting that it exists, while Joona Räsänen has recently criticized their reasoning. We respond to Räsänen’s analysis, concluding that his arguments are unsuccessful, and that there is no right to the death of the foetus in these circumstances. 相似文献
6.
Johan T. Ruud 《Helgoland Marine Research》1968,17(1-4):510-517
Summary 1. The material for this study is drawn from two sources, (a) investigations of the fish fauna in the inner Oslofjord between 1897 and 1967, (b) fish landing statistics available since 1872 at the Oslo fish market.2. The investigations of the fish fauna reveal that 4 species of fish — 2 sharks and 2 arctic bullheads — have disappeared from the deep waters of the Oslofjord where they were known to exist in 1897. We assume that unfavourable conditions, great changes in temperature or lack of oxygen in the stagnant deep water to which these species belonged have been injurious to their propagation and survival.3. The annual fluctuations in the landed quantities of fish are great, but nevertheless there exists a marked decreasing trend since about 1930; total landings in recent years are less than 1/10 of what they were 30 or 40 years ago.4. The fluctuations in the landings of cod, herring and mackerel are studied in some detail. Three periods (of 20 to 22 years' duration) from 1872 to 1932 show increasing average landings of cod: 44, 57, and 74 tons respectively; in the period 1933 to 1955 landings decreased to an average of 16 tons per year. The effect of fluctuating year classes is discussed.5. The landings of herring and mackerel were very good between 1911 and 1919 or 1920 with a maximum of 1500 tons of herring and 800 tons of mackerel. In the following years there was a trend of decrease with a few years of moderately good landings. Mature mackerels are immigrating into the fjord for feeding and spawning, while mature herrings, to a major extent, are supposed to belong to a local stock. The highest landings of both species are due to extremely great catches of young fish, and the success of the fishery in any one year, therefore, dependent of a successful spawning and hatching one ort two years before.6. In conclusion, the attention is drawn to the fact that there are reasons to believe that the profuse growth of bacteria in the polluted waters seems to be injurious to the hatching of fish eggs and to the survival of fish larvae (Dannevig 1945,Oppenheimer 1955).
Veränderungen der Fischfauna und der Fischerei des Oslofjords seit der Jahrhundertwende
Kurzfassung Das Material zu dieser Untersuchung stammt aus zwei Quellen: (a) vier Untersuchungen über die Fischfauna des Oslofjords im Zeitraum zwischen 1897 und 1967, und (b) Statistiken für den Zeitraum von 1872 bis 1964 über die Fischmengen, die im inneren Oslofjord gefangen und an die Fischhalle in Oslo geliefert worden sind. Ein Vergleich der Resultate mit den vier Untersuchungen über die Fischfauna zeigt, daß vier Arten von Tiefwasserfischen aus dem inneren Oslofjord völlig verschwunden sind, nämlichEtmopterus spinax, Somniosus microcephalus, Artediellus uncinatus undIcelus bicornis, die beiden zuletzt genannten wahrscheinlich schon vor 1930. Eine Anzahl anderer Arten, die früher häufig waren, sind jetzt selten. Statistische Erhebungen über die im Oslofjord gefangenen Fische lassen erkennen, daß die Erträge seit den zwanziger und dreißiger Jahren stark zurückgegangen sind. Gleichzeitig hat die Zahl der Fischer abgenommen. Es wird die Schlußfolgerung gezogen, daß die Veränderungen des Oslofjords sich besonders in den letzten 30 Jahren für mehrere Fischarten als schädigend erwiesen haben. Diese Auffassung wird unterstützt durch die Untersuchungen vonDannevig (1945) undOppenheimer (1955), die gezeigt haben, daß die reiche Bakterienflora des Oslofjords für die Entwicklung der pelagischen Fischeier schädlich ist.相似文献
7.
Understanding the role of the cytoskeleton in the complex regulation of the endothelial repair 总被引:1,自引:0,他引:1
Actin microfilaments and microtubules are important cytoskeletal proteins that regulate endothelial repair through alterations in cell shape and through regulation of cell migration following wounding of the endothelium. Upstream pathways have been identified in the regulation of actin and microtubule organization, especially small GTPases. Recently, there have been numerous proteins suggested to be capable of regulating interaction between microtubules and microfilaments to mediate microtubule regulation of endothelial repair, an important process in limiting injury to the artery wall and in reducing the extent of arterial disease. If disrupted, a rapid repair mechanism is important in reestablishing the integrity of the endothelium in order to reestablish its function as a macromolecular barrier, a thromboresistant surface, and a biologically active tissue. Strategies to improve repair should alter the pathobiology of the atherosclerotic plaque and thus improve the prognosis of patients with atherosclerosis. 相似文献
8.
A I Gorbachevskaia 《Arkhiv anatomii, gistologii i émbriologii》1988,95(9):11-17
The investigation has been performed on the cat by means of the retrograde axonal transport of horseradish peroxidase method and luminescent markers. To the putamen along its rostro-caudal length and to all the segments projection fibers get only from the neurons of the basal nucleus of the amygdaloid body, greater number of the neurons projecting to the antero-ventral parts of the putamen than to the posterior ones. The problem on likeness in organization of the projections of the amygdaloid body and the caudate nucleus is discussed. 相似文献
9.
V N Kiro? 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1988,38(1):40-44
On the basis of analysis of the results of author's studies and literature data, theoretical notions are developed, according to which spatial-temporal organization of cortical biopotentials is a result of activity of nonspecific different level systems subtly regulating current alertness in conformity with needs of the actual and forthcoming activities. In the hierarchy of regulating systems, in conditions of alertness, nonspecific thalamic and midbrain system is leading. Activity of these regulation levels provides in alertness for formation and destruction of functional neuronal ensembles which realize elementary informational transformations. The role is emphasized of asynchronous processes in the central nervous system activity. 相似文献
10.
A G Zara?ski? 《Ontogenez》1991,22(4):365-374
Experiments were performed using X. laevis embryos during gastrulation and neurulation (stages 10, 11 1/2, 12 1/2, 13 1/2, 15 and 18). Part of presumptive epidermis and lateral plate mesoderm was removed, and embryos raised until stage 25. The size of axial structures (notochord, somite mesoderm, central nervous system) was determined using serial histological sections and compared with that of control embryos. In experimental embryos, the size of axial structures was decreased. Until a specific stage of development, close correlation was found between the volume of embryonic compartment corresponding to a particular, structure and the volume of presumptive epidermis and lateral plate mesoderm. This stage is individual for each axial organ: middle gastrula (stage 11 1/2) for notochord, late gastrula (stage 12 1/2) for somite mesoderm, and late neurula (stage 18) for central nervous system. This data suggest that differentiation pattern of ecto-mesodermal rudiment is subject to regulation during gastrulation-neurulation, and subdivision of ectoderm and mesoderm into axial and non-axial tissues is a self-organizing process. 相似文献
11.
On the diversity of the Cladocera in the tropics 总被引:20,自引:13,他引:7
Henri J. Dumont 《Hydrobiologia》1994,272(1-3):27-38
The mythical concept of an impoverished tropical cladoceran fauna is refuted. On a planetary scale, around half of the cladoceran species presently known occur exclusively in the tropics-subtropics, often with considerable restriction to particular geographical subzones. On a regional (political) scale, the situation is often unclear because of the continued fragmentary nature of studies, and because political units are not a good basis for biogeographical comparisons. At the finest level of resolution (lake-perlake comparisons), there appears to be an upper limit of c. 50 cladoceran species per individual lake. No significant difference between lakes in the temperate zone and in the tropics could be established here. Daphnia is largely absent from the tropics, but is replaced by more Sidids, Moinids, and Bosminids, such that the average cladoceran community in the limnetic zone of a tropical lake is not characterized by less species but rather by lower population densities. This, in turn, is considered a consequence of higher prevalent predation levels in the tropics. 相似文献
12.
J. Kozk 《Biometrical journal. Biometrische Zeitschrift》1991,33(5):607-612
When constructing predictors on the basis of the linear model of time series of various indicators often the question arises on the dependence of forecasting accuracy and the changing prediction horizon. The dependency of the quadratic risk of the classical predictor and the time horizon is considered. 相似文献
13.
DNA contents in squashed cells of the adult frog hypothalamic preoptic region (HPR) were measured using the Feulgen and UV cytophotometry techniques. The histone-DNA ratio in the cell nucleus was determined by means of a combined Feulgen-heparin-Alcian blue staining procedure. The nuclei of the vast majority of HPR cells have a diploid DNA content. However, in cells of this group the mean values of DNA amount and the distribution range were always higher than those in hepatocytes used as a diploid standard. Such a heterogeneity in DNA content in the diploid part of HPR cell population could apparently suggest some differences in the nuclear chromatin arrangement to be always higher in spring before the frog spawning, and it seems to be characteristic of this type of cells. About 1 per cent of cells with hyperdiploid surplus of DNA (H2c cells) as well as of tetraploid cells (4c and 2c X 2 cells) is found in HPR in frogs sacrificed both in winter and in summer. The quota of these cells has no reference either to the frog's age or to the annual cycle. The fact that the mean DNA values in H2c and 4c cells are much higher than in the standard cannot be explained by the presence of different amounts of nuclear proteins only. It is suggested that at least some part of the highest DNA values may be due to an actual extra DNA synthesis in a small constantly existing pool of HPR cell population. 相似文献
14.
Pauline M. Bennett 《Biophysical reviews》2018,10(4):955-959
Cardiomyocytes interact with each other at their ends through the specialised membrane complex, the intercalated disck (ID). It is a fascinating structure. It allows cardiomyocytes to interact with several neighbouring cells, thereby allowing the complex structure of the heart to develop. It acts as tension transducer, structural prop, and multi signalling domain as well as a regulator of growth. It achieves its many functions through a number of specialised domains and intercellular junctions associated with its complex folded membrane. This review outlines the results of some 20 years of fascination with the ups and downs of the ID. These include locating the spectrin-associated membrane cytoskeleton in the ID and investigating the role of Protein 4.1R in calcium signalling; structural studies of the relationship of the ID to myofibrils, sarcoplasmic reticulum and mitochondria and, finally, consideration of the role of the ID in cardiomyocyte growth and heart disease. 相似文献
15.
Drainage of the prelymphatics of the brain via the adventitia of the vertebral artery 总被引:5,自引:0,他引:5
Carbon particles injected into the cortex of the cerebellum of the rat were found in the Virchow-Robin spaces of the adjacent capillaries, and in the adventitia of the cerebellar artery, basilar artery and vertebral artery--both inside and outside the skull. They were also found in some portions of the deeper cervical lymph nodes. However, while tracers injected into the cerebral hemispheres are drained via the tissue channels in the adventitia of the internal carotid arteries, tracers injected into the cerebellar hemispheres are drained via those of the vertebral arteries. 相似文献
16.
On 50 brains of newborns of either sex, the exterior and interior morphology was studied. The exterior morphology of the brain was conformable to the configuration of the skull. The insula is relatively large, but extremely inadequately grooved. The subcortical masses are well pronounced but there is in general a very slight difference between the white and gray matter of the brain. The convolutions and grooves of the cerebellum are very distinctly marked, the nucleus dentatus is large and white matter is prevalent. The brain stem is rather well formed, distinctly plastic, this being particularly true for the region of the rhomboid fossa and medulla oblongata. 相似文献
17.
《Journal of Russian & East European Psychology》2013,51(4):46-53
The time has come to proceed from forms of givenness of the word to forms of the word as such. They can, if you like, be called external and inner structures. Humboldt, however, preferred to speak of the external and inner forms of the language. Shpet adopted precisely this distinction. Why did this problem interest Shpet? Already in [Appearance and sense], he had set the task of returning to the source of pretheoretical, living science. Shpet wrote that the outer cover of words and logical expressions obscure the objectified meaning and that it was necessary to remove another cover from the objectified sign so as to grasp a certain genuine intimacy, and in it the fullness of being (Shpet, 1914. Pp. 5-6). We shall keep in mind this major undertaking posed by this scientist. The existence of the inner form of words should not come as a surprise. That same year (1914) Ortega y Gasset wrote that material objects have a third dimension. However, we cannot see or touch it: "For just as depth needs a surface beneath which to be concealed, the surface, or outer cover, in order to be so, needs something over which to spread, covering it" (Ortega y Gasset, 2000. Pp. 62-63). 相似文献
18.
Brachyury, the blastopore and the evolution of the mesoderm 总被引:3,自引:0,他引:3
Technau U 《BioEssays : news and reviews in molecular, cellular and developmental biology》2001,23(9):788-794
The role of Brachyury and other T-box genes in the differentiation of mesoderm and endoderm of vertebrates is well established. Recently, homologues of Brachyury have been isolated from an increasing number of diverse organisms ranging from Cnidaria to vertebrates and insects. Comparative expression and function analysis allows the origin of the mesoderm and the evolution of the developmental role of Brachyury gene family in metazoans to be traced. The data suggest that an ancestral function of Brachyury was to designate a blastoporal region that had distinct properties in induction and axis elongation. A subset of blastoporal cells expressing Brachyury and other genes that convey specific mesodermal functions may have segregated as a distinct cell population from this region in the course of mesoderm evolution. 相似文献
19.
The retina of the vertebrate eye is metabolically active and requires nutritive support. During the last 540 million years it has evolved into forms as complicated and nutritionally demanding as those found in avian or primate eyes. Diffusion from the choroid is generally able to supply the metabolic needs of thin retinae. However, when the thickness exceeds the limits of diffusion, structures are needed to supplement the vascular supply from the choroid. These supplemental nutritive devices include the choroidal gland, the falciform process and preretinal vascular plexus of fish, the conus papillaris of lizards, the pecten oculi of birds, the intraretinal vessels of mammals and a few novel systems that remain difficult to classify. These vascular systems are among the most variable features of the vertebrate eye. Here, we review classical and recent findings regarding such retinal nutrition systems, propose a three category classification for them based on histologic origins and speculate on the evolutionary forces which drove their development. 相似文献
20.
Nearly 50 years have elapsed since Hayflick challenged the dogma that individual human cells were immortal by demonstrating that after a predictable number of cellular divisions, normal human fibroblasts eventually entered a state of permanent growth arrest [Hayflick L: The limited in vitro lifetime of human diploid cell strains. Exp Cell Res 1965, 37:614-636.; Hayflick L, Moorhead PS: The serial cultivation of human diploid cell strains. Exp Cell Res 1961, 25:585-621]. This growth arrest, referred to as senescence, was hypothesized to function as a tumor suppressive mechanism, capable of limiting the replicative capacity of an incipient tumor cell. While originally met with skepticism, the existence of senescence and its importance as a tumor suppressive mechanism is now accepted. Here, we highlight this work and introduce studies that indicate that while senescent cells themselves cannot produce a neoplasia, they possess the ability to promote the growth of nearby preneoplastic cells and in this way may contribute to age-related increases in tumor incidences. This added level of complexity suggests that senescence functions as a biological 'double edged sword.' 相似文献