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Coelomic Cavity (coelomic + cavity)
Selected AbstractsWhen an epithelium ceases to exist , an ultrastructural study on the fate of the embryonic coelom in Epiperipatus biolleyi (Onychophora, Peripatidae)ACTA ZOOLOGICA, Issue 3 2004Georg Mayer Abstract It is an accepted fact that fusion between the coelomic cavities and the primary body cavity occurs during development in the Arthropoda. However, such a fusion is much disputed in the Onychophora. In order to clarify this subject, the fate of embryonic coelomic cavities has been studied in an onychophoran. Ultrastructural investigations in this paper provide evidence that embryonic coelomic cavities fuse with spaces of the primary body cavity in Epiperipatus biolleyi. During embryogenesis, the somatic and splanchnic portions of the mesoderm separate and the former coelomic linings are transformed into mesenchymatic tissue. The resulting body cavity therefore represents a mixture of primary and secondary (coelomic) body cavities, i.e. the ,mixocoel'. The nephridial anlage is already present, when the ,mixocoel' is formed, although there is no trace of a sacculus yet. The lumen of the nephridial anlage, thus, communicates with the newly formed ,mixocoel'. Accordingly, the lumen of the nephridial sacculus cannot be regarded as a kind of ,persisting coelomic cavity' in E. biolleyi. Our findings support the hypothesis that the ,mixocoel' was already present in the common stem species of the Onychophora and Euarthropoda. [source] The role of character loss in phylogenetic reconstruction as exemplified for the AnnelidaJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 4 2007C. Bleidorn Abstract Annelid relationships are controversial, and molecular and morphological analyses provide incongruent estimates. Character loss is identified as a major confounding factor for phylogenetic analyses based on morphological data. A direct approach and an indirect approach for the identification of character loss are discussed. Character loss can frequently be found within annelids and examples of the loss of typical annelid characters, like chaetae, nuchal organs, coelomic cavities and other features, are given. A loss of segmentation is suggested for Sipuncula and Echiura; both are supported as annelid ingroups in molecular phylogenetic analyses. Moreover, character loss can be caused by some modes of heterochronic evolution (paedomorphosis) and, as shown for orbiniid and arenicolid polychaetes, paedomorphic taxa might be misplaced in phylogenies derived from morphology. Different approaches for dealing with character loss in cladistic analyses are discussed. Application of asymmetrical character state transformation costs or usage of a dynamic homology framework represents promising approaches. Identifying character loss prior to a phylogenetic analysis will help to refine morphological data matrices and improve phylogenetic analyses of annelid relationships. Zusammenfassung Die Phylogenie der Annelida wird nach wie vor kontrovers diskutiert und morphologische und molekulare Analysen liefern hierbei unterschiedliche Ergebnisse. Merkmalsverluste können phylogenetische Analysen morphologischer Daten in die Irre führen. In der vorliegenden Arbeit werden ein direkter und ein indirekter Ansatz zur Erkennung von Merkmalsverlusten vorgestellt. Es wird gezeigt, dass Merkmalsverlust innerhalb der Anneliden häufig auftritt und das hiervon auch typische Annelidenmerkmale, wie z.B Borsten, Nuchalorgane oder Coelomräume betroffen seien können. Molekularphylogenetische Analysen unterstützen eine Stellung der Echiura und Sipuncula innerhalb der Anneliden und somit ist für diese Taxa ein Verlust der Segmentierung anzunehmen. Es wird demonstriert, dass Merkmalsverlust durch herterochrone Evolution verursacht werden kann. Am Beispiel von Orbiniiden und Arenicoliden wird gezeigt, wie paedomorphe Taxa in kladistischen Analysen morphologischer Daten falsch platziert werden. Verschiedene Ansätze zum Umgang mit Merkmalsverlust in morphologischen Datensätzen werden präsentiert und diskutiert. Hierbei stellen die Verwendung asymmetrischer Merkmalstransformationskosten oder die Verwendung dynamischer Homologiehypothesen aussichtsreiche Ansätze dar. Jedoch werden für alle Ansätze Phylogeniehypothesen benötigt, die in einer Analyse unabhängiger Daten (bspw. Moleküle) erstellt wurden, um Merkmalsverluste sicher zu identifizieren. [source] Three-dimensional trajectories of 60Co-labelled earthworms in artificial cores of soilEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2001Y. Capowiez Summary Information on earthworm burrowing behaviour is scarce and therefore the evolution of the macroporosity related to earthworm activities is still poorly known. We have designed a new apparatus, ,Colonne Gamma', to follow the three-dimensional trajectories of radio-labelled earthworms in artificial cores of soil. Earthworms are radio-labelled by injecting into their coelomic cavity a small source of 60Co (volume 0.1 mm3, intensity 13.5 ,Ci). The emission of gamma rays is recorded by three detectors carried by a disc that oscillates vertically around the soil core where the earthworm is introduced. We have also developed a deterministic model to estimate the positions of the 60Co source from the number of gamma rays received by each detector during an oscillation. Numerical experiments showed that the uncertainties of estimates were less than 3 mm for each coordinate. To validate the results, we tracked the trajectory (one position every 4 minutes) of a radio-labelled earthworm for 1 week and compared it with the skeleton of the macroporosity obtained by computer assisted tomography of the same soil core. There was a general qualitative agreement between the trajectory and the skeleton. Moreover, based on the precise study of the successive positions of the earthworm we could distinguish two different kinds of activities in the trajectory: displacement and digging events. The ,Colonne Gamma' apparatus therefore has great potential for studies of the ecology and the behaviour of earthworms. [source] Ultrastructure of the body cavities in Phylactolaemata (Bryozoa)JOURNAL OF MORPHOLOGY, Issue 3 2009Alexander Gruhl Abstract Only species belonging to the bryozoan subtaxon Phylactolaemata possess an epistome. To test whether there is a specific coelomic cavity inside the epistome, Fredericella sultana, Plumatella emarginata, and Lophopus crystallinus were studied on the ultrastructural level. In F. sultana and P. emarginata, the epistome contains a coelomic cavity. The cavity is confluent with the trunk coelom and lined by peritoneal and myoepithelial cells. The lophophore coelom extends into the tentacles and is connected to the trunk coelom by two weakly ciliated coelomic ducts on either side of the rectum. The lophophore coelom passes the epistome coelom on its anterior side. This region has traditionally been called the forked canal and hypothesized to represent the site of excretion. L. crystallinus lacks an epistome. It has a simple ciliated field where an epistome is situated in the other species. Underneath this field, the forked canal is situated. Compared with the other species, it is pronounced and exhibits a dense ciliation. Despite the occurrence of podocytes, which are prerequisites for a selected fluid transfer, there is no indication for an excretory function of the forked canal, especially as no excretory porus was found. J. Morphol. 2009. © 2008 Wiley-Liss, Inc. [source] The contribution of the swimbladder to buoyancy in the adult zebrafish (Danio rerio): A morphometric analysisJOURNAL OF MORPHOLOGY, Issue 6 2008George N. Robertson Abstract Many teleost fishes use a swimbladder, a gas-filled organ in the coelomic cavity, to reduce body density toward neutral buoyancy, thus minimizing the locomotory cost of maintaining a constant depth in the water column. However, for most swimbladder-bearing teleosts, the contribution of this organ to the attainment of neutral buoyancy has not been quantified. Here, we examined the quantitative contribution of the swimbladder to buoyancy and three-dimensional stability in a small cyprinid, the zebrafish (Danio rerio). In aquaria during daylight hours, adult animals were observed at mean depths from 10.1 ± 6.0 to 14.2 ± 5.6 cm below the surface. Fish mass and whole-body volume were linearly correlated (r2 = 0.96) over a wide range of body size (0.16,0.73 g); mean whole-body density was 1.01 ± 0.09 g cm,3. Stereological estimations of swimbladder volume from linear dimensions of lateral X-ray images and direct measurements of gas volumes recovered by puncture from the same swimbladders showed that results from these two methods were highly correlated (r2 = 0.85). The geometric regularity of the swimbladder thus permitted its volume to be accurately estimated from a single lateral image. Mean body density in the absence of the swimbladder was 1.05 ± 0.04 g cm,3. The swimbladder occupied 5.1 ± 1.4% of total body volume, thus reducing whole-body density significantly. The location of the centers of mass and buoyancy along rostro-caudal and dorso-ventral axes overlapped near the ductus communicans, a constriction between the anterior and posterior swimbladder chambers. Our work demonstrates that the swimbladder of the adult zebrafish contributes significantly to buoyancy and attitude stability. Furthermore, we describe and verify a stereological method for estimating swimbladder volume that will aid future studies of the functions of this organ. J Morphol., 2008. © 2008 Wiley-Liss, Inc. [source] A New Look on the Origin of the Gonad and the Müllerian Duct: the Sturgeon (Acipencer) as a Model for Vertebrate Urogenital DevelopmentANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005K. -H. The origin of the vertebrate gonad and the Müllerian duct are still a matter of debate. According to the majority of recent textbooks, the gonad is a product of the proliferating coelothelium and therefore derived from the mesoderm of the lateral plate region. The Müllerian duct grows parallel to the Wolffian duct, but it is not clear to what extent the latter contributes actively to the development of the former. In the last decade, we reinvestigated early gonadogenesis and Müllerian duct development in a number of vertebrate model species using various morphological techniques (TEM, SEM, immunohistochemistry). The conclusion of our studies is that rudimentary or regressing nephrostomial tubules, particularly cells of their nephrostomes, must be regarded as the immediate precursors of the somatic cells of the gonadal crest and the Müllerian infundibular field. According to this concept, both structures are derivatives of the intermediate mesoderm. Nephrostomial tubules are regular components of the primitive pro- and mesonephros. They connect the nephric tubule or the nephric corpuscle to the coelomic cavity and open into the latter by means of a funnel-like mouth, the nephrostome (coelomostome). In the larval sterlet, Acipenser ruthenus, short, segmentally arranged nephrostomial tubules with well-developed nephrostomes are present in the region of the cranial opisthonephros. Cells of the medial nephrostomial lips proliferate, surround the germ cells that have accumulated in this location and form a continuous gonadal crest. Cells of the lateral nephrostomial lips proliferate also, spread out on the coelomic surface, replace the original flat mesothelial cells over the Wolffian duct and the cranial opisthonephros and form the Müllerian infundibular field. At about 28 days, a flat pocket begins to invaginate the infundibular field. This pocket is the primordium of the Müllerian ostium abdominale. The findings in Acipenser can be generalized and transferred to other vertebrates. [source] Development of germ cells and reproductive biology in the sipunculid Phascolosoma esculentaAQUACULTURE RESEARCH, Issue 3 2009Xue-Ping Ying Abstract Sipuncula are of increasing interest for fisheries and aquaculture in China. Sustainable harvests will rely on a better knowledge of reproductive characteristics and stock enhancement. Here, we investigated the structural characteristics of and seasonal changes in germ cell development of the sipunculid Phascolosoma esculenta from the south-eastern coast of Zhejiang, China. An annual survey of egg numbers in the coelom (body cavity) fluid by light and electron microscopy of the females indicates that P. esculenta is dioecious. No defined gonad but dissociated germ cells were found in the coelomic cavity during the 1-year observation. The germ cells showed multiplication and development in the coelomic cavity. Reproduction took place from May to September, with a peak in July and August. The oogenesis can be divided into four phases: cell proliferation, pre-vitellogenesis, vitellogenesis and egg envelope formation and maturation. The process of spermatogenesis can also be divided into four phases: cell multiplication, cell growth, cell maturation and metamorphosis. Monthly changes in the relative number of eggs in each stage indicate that P. esculenta lays eggs in batches. The sperm thrives in the coelomic fluid in the form of cell groups with patterns of genesis and release similar to those of the eggs. Eggs of P. esculenta were fertilized only when reaching the nephridium. The sex ratio was about 1:1 throughout the year. [source] When an epithelium ceases to exist , an ultrastructural study on the fate of the embryonic coelom in Epiperipatus biolleyi (Onychophora, Peripatidae)ACTA ZOOLOGICA, Issue 3 2004Georg Mayer Abstract It is an accepted fact that fusion between the coelomic cavities and the primary body cavity occurs during development in the Arthropoda. However, such a fusion is much disputed in the Onychophora. In order to clarify this subject, the fate of embryonic coelomic cavities has been studied in an onychophoran. Ultrastructural investigations in this paper provide evidence that embryonic coelomic cavities fuse with spaces of the primary body cavity in Epiperipatus biolleyi. During embryogenesis, the somatic and splanchnic portions of the mesoderm separate and the former coelomic linings are transformed into mesenchymatic tissue. The resulting body cavity therefore represents a mixture of primary and secondary (coelomic) body cavities, i.e. the ,mixocoel'. The nephridial anlage is already present, when the ,mixocoel' is formed, although there is no trace of a sacculus yet. The lumen of the nephridial anlage, thus, communicates with the newly formed ,mixocoel'. Accordingly, the lumen of the nephridial sacculus cannot be regarded as a kind of ,persisting coelomic cavity' in E. biolleyi. Our findings support the hypothesis that the ,mixocoel' was already present in the common stem species of the Onychophora and Euarthropoda. [source] | |||||||||||||