The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform

Andrea Mess - One of the best experts on this subject based on the ideXlab platform.

  • Chorioallantoic and yolk sac placentation in the dassie rat Petromus typicus and its significance for the evolution of hystricognath rodents.
    Placenta, 2007
    Co-Authors: Andrea Mess
    Abstract:

    Placental characters are most important in understanding the evolutionary history of hystricognath rodents of which some act as animal models for human pregnancy. The data available deal mostly with Species native to South America, but the current paper presents novel findings on chorioallantoic and yolk sac placentation in an Old World hystricognath and discusses its significance for the evolution of the group. Several hystricognath Stem Species characters are verified for Petromus, such as the unique trophoblast growth pattern within the chorioallantoic placenta. Subsequently, a novel set of characters belonging to the visceral yolk sac is added to the Stem Species pattern of the group. The nourishment of the embryo is facilitated by an inverted visceral yolk sac placenta from early pregnancy onward, later complemented by the chorioallantoic placenta. About mid term, the visceral yolk sac becomes partly folded and attached to the parietal yolk sac cover of the chorioallantoic placenta, suggesting a functional shift to the transfer of substances between the two placental types. Thus, the chorioallantoic and yolk sac placenta collaborate in nurturing the embryo. This apparently represents an evolutionary transformation along the Stem lineage of hystricognaths.

  • Development of the chorioallantoic placenta in Octodon degus—a model for growth processes in caviomorph rodents?
    Journal of Experimental Zoology, 2007
    Co-Authors: Andrea Mess
    Abstract:

    The degu Octodon degus is one of the very few members of caviomorph or hystricognath Rodentia that possesses a simply arranged chorioallantoic placenta without advanced lobulation. Therefore this Species was used as a model to study regional development and growth processes of the placenta, based on the examination of 20 individuals by light and electron microscopy as well as by using markers for proliferation, trophoblast and endometrial stroma. The results were interpreted by comparison with other hystricognaths in the light of their evolutionary history. It was found that trophoblast derived from the trophospongium is essential for extension of the placenta including the labyrinth: extensive proliferation is restricted to trophoblast cells at the outer margin of the placenta and along internally directed, finger-tip like protrusions of fetal mesenchyme towards the labyrinth. This kind of placental development is regarded as part of the Stem Species pattern of hystricognaths, evolved more than 40 million years ago. It is indicated for the first time that the replenishment of the syncytiotrophoblast is similar to corresponding processes in the human placenta. In conclusion, the degu is a useful model for placental growth dynamics, particularly because of its simply arranged placental architecture, and may also serve as an animal model in comparison to human pregnancies. J. Exp. Zool. (Mol. Dev. Evol.) 308B:371–383, 2007. © 2007 Wiley-Liss, Inc.

  • The subplacenta in Octodon degus and Petromus typicus--two hystricognath rodents without significant placental lobulation.
    Journal of Experimental Zoology, 2007
    Co-Authors: Andrea Mess
    Abstract:

    Until now, defining characters of hystricognath rodents have been the subplacenta and the lobulation of the main chorioallantoic placenta. However, recent studies have revealed hystricognaths without marked lobulation, which is a plesiomorphic condition of the group. The question thus arises whether the subplacenta of these taxa is structurally homologous to that of other hystricognaths. Therefore, subplacental morphology and ontogeny were investigated in Octodon and Petromus by conventional light and electron microscopy, and the Stem Species pattern of Hystricognathi was reconstructed by applying MacClade™. The subplacentae of both Species share important similarities with other hystricognaths. The organ develops early in gestation but degenerates towards term. It consists of folded layers of cellular and syncytial trophoblast, the latter enclosing maternal blood lacunae and electron-dense particles. Root-like syncytial outgrowths (syncytial streamers) and extraplacental trophoblast cells occur at the lateral and basal borders of the organ. Maternal vascularisation by blood lacunae within the subplacental syncytiotrophoblast is acquired early but lost during mid-gestation. Vascularisation by fetal vessels is established later. Fetomaternal exchange via blood circulation inside the subplacenta is unlikely to occur, since periods of maternal and fetal vascularisation show little overlap. In conclusion, the subplacentae of both Species are regarded as homologous to other hystricognaths, comprising 18 character conditions that belong to their Stem Species pattern. Thus, the syStematic unity of the group can be confirmed. J. Exp. Zool. (Mol. Dev. Evol.) 306B, 2006. © 2006 Wiley-Liss, Inc.

  • Evolutionary differentiation of Cetartiodactyl placentae in the light of the viviparity-driven conflict hypothesis.
    Placenta, 2006
    Co-Authors: K. Klisch, Andrea Mess
    Abstract:

    Abstract We analysed the evolution of placental traits in the novel mammalian clade Cetartiodactyla (Cetaceans and Artiodactyls) by a parsimony-based computer program (MacClade). A diffuse epitheliochorial placenta was identified as the Stem Species pattern of this clade. Trophoblast giant cells (TGCs) independently evolved in Camelids and Ruminants. The polycotyledonary placenta is an apomorphic character for Pecora (higher ruminants) and the oligocotyledonary placenta developed as a further step on the Stem lineage of cervidae and moschidae. We interpret these findings by application of the “viviparity-driven conflict hypothesis”, which states that divergent interests of mother and offspring lead to a rapid antagonistic coevolution, which might cause placental diversity. According to this hypothesis the evolution of camelid and ruminant TGCs can be interpreted as means to increase fetal endocrine influence on the maternal metabolism. The development of the cotyledonary placenta could be related to a diminished availability of glucose, which is associated with the evolution of forestomach fermentation in Pecora. An arms race, in which the mother tried to restrict and the fetus tried to increase transplacental glucose flow, might have promoted the evolution of the cotyledonary placenta, which has a high feto-maternal exchange area, but a low conductivity for glucose.

  • evolutionary transformations of fetal membrane characters in eutheria with special reference to afrotheria
    Journal of Experimental Zoology, 2006
    Co-Authors: Andrea Mess, A M Carter
    Abstract:

    Analysis of molecular data sets has provided new insights into higher-level relationships of living Eutheria, including the recognition of Afrotheria as a novel taxon. This offers an opportunity to take a fresh look at the evolution of organ syStems, including some that are little used in traditional syStematics. In the present study, we attempted a reconstruction of the evolution of characters associated with placentation, the fetal membranes and the female reproductive tract. The evolutionary history of 21 characters has been traced, based on a current hypothesis of eutherian relationships, by applying the computer program MacClade. Accordingly, the analysis provides a first comprehensive interpretation of the Stem Species pattern of Eutheria. Of particular note, this pattern includes an endotheliochorial chorioallantoic placenta. The reconstructed pattern of Eutheria does not change in the basal nodes of the group. Thus, no character transformations occur on the Stem lineages of Laurasiatheria or Euarchontoglires, and even Afrotheria has mostly plesiomorphic character conditions. However, two character transformations occur on the common Stem lineage of Afrotheria and its sister taxon Xenarthra, i.e., amniogenesis by cavitation instead of folding and the precocial state of the newborn. In addition, we recognized one character transformation on the Stem lineage of Afrotheria, i.e., the occurrence of a four-lobed allantoic sac. Thus, contrary to previous assertions, it is possible to identify morphological characters that could be synapomorphic for this novel taxon. J. Exp. Zool. (Mol. Dev. Evol.) 306B, 2006. © 2005 Wiley-Liss, Inc.

Giorgio Manzi - One of the best experts on this subject based on the ideXlab platform.

  • the Stem Species of our Species a place for the archaic human cranium from ceprano italy
    PLOS ONE, 2011
    Co-Authors: Aurelien Mounier, Silvana Condemi, Giorgio Manzi
    Abstract:

    One of the present challenges in the study of human evolution is to recognize the hominin taxon that was ancestral to Homo sapiens. Some researchers regard H. heidelbergensis as the Stem Species involved in the evolutionary divergence leading to the emergence of H. sapiens in Africa, and to the evolution of the Neandertals in Europe. Nevertheless, the diagnosis and hypodigm of H. heidelbergensis still remain to be clarified. Here we evaluate the morphology of the incomplete cranium (calvarium) known as Ceprano whose age has been recently revised to the mid of the Middle Pleistocene, so as to test whether this specimen may be included in H. heidelbergensis. The analyses were performed according to a phenetic routine including geometric morphometrics and the evaluation of diagnostic discrete traits. The results strongly support the uniqueness of H. heidelbergensis on a wide geographical horizon, including both Eurasia and Africa. In this framework, the Ceprano calvarium – with its peculiar combination of archaic and derived traits – may represent, better than other penecontemporaneous specimens, an appropriate ancestral stock of this Species, preceding the appearance of regional autapomorphic features.

Stefan Richter - One of the best experts on this subject based on the ideXlab platform.

  • Phylogeny of the Anomala (Crustacea, Decapoda, Reptantia) based on the ossicles of the foregut
    Zoologischer Anzeiger – A Journal of Comparative Zoology, 2011
    Co-Authors: André Reimann, Stefan Richter, Gerhard Scholtz
    Abstract:

    We present a cladistic analysis of the Anomala based on 66 ingroup Species and 5 outgroup representatives. Based on a comparative analysis of the morphology of the foregut we scored 124 characters related to size, shape, and fusion of foregut ossicles and other foregut structures. Our parsimony analysis resulted in 30 equally parsimonious trees which differ mainly at the lower hierarchical level. Our study reveals two large clades within Anomala. One large clade consists of Galatheoidea and Chirostyloidea. The internal relationships show a monophyletic Porcellanidae nested within a group comprising paraphyletic Galatheidae, and Munididae as well as Munidopsidae. The other large clade contains Aegla as sister group to a monophyletic group consisting of the Hippoidea and a clade formed by Lomis and the Paguroidea. Coenobitidae are nested within paraphyletic Diogenidae and Lithodidae are nested within paraphyletic Paguridae. The results are discussed in the context of other morphological and molecular analyses. Furthermore, some aspects of carcinization are touched upon; in particular, an anomalan Stem Species with a, at least to some extent, ventrally folded pleon is suggested.

  • Regular articlePhylogenetic syStematics of the reptantian Decapoda (Crustacea, Malacostraca)
    Zoological Journal of the Linnean Society, 1995
    Co-Authors: Gerhard Scholtz, Stefan Richter
    Abstract:

    Although the biology of the reptantian Decapoda has been much studied, the last comprehensive review of reptantian syStematics was published more than 80 years ago. We have used cladistic methods to reconstruct the phylogenetic syStem of the reptantian Decapoda. We can show that the Reptantia represent a monophyletic taxon. The classical groups, the ‘Palinura’, ‘Astacura’ and ‘Anomura’ are paraphyletic assemblages. The Polychelida is the sister-group of all other reptantians. The Astacida is not closely related to the Homarida, but is part of a large monophyletic taxon which also includes the Thalassinida, Anomala and Brachyura. The Anomala and Brachyura are sister-groups and the Thalassinida is the sister-group of both of them. Based on our reconstruction of the sister-group relationships within the Reptantia, we discuss alternative hypotheses of reptantian interrelationships, the syStematic position of the Reptantia within the decapods, and draw some conclusions concerning the habits and appearance of the reptantian Stem Species.

  • Phylogenetic syStematics of the reptantian Decapoda (Crustacea, Malacostraca)
    Zoological Journal of the Linnean Society, 1995
    Co-Authors: Gerhard Scholtz, Stefan Richter
    Abstract:

    Although the biology of the reptantian Decapoda has been much studied, the last comprehensive review of reptantian syStematics was published more than 80 years ago. We have used cladistic methods to reconstruct the phylogenetic syStem of the reptantian Decapoda. We can show that the Reptantia represent a monophyletic taxon. The classical groups, the ‘Palinura’, ‘Astacura’ and ‘Anomura’ are paraphyletic assemblages. The Polychelida is the sister-group of all other reptantians. The Astacida is not closely related to the Homarida, but is part of a large monophyletic taxon which also includes the Thalassinida, Anomala and Brachyura. The Anomala and Brachyura are sister-groups and the Thalassinida is the sister-group of both of them. Based on our reconstruction of the sister-group relationships within the Reptantia, we discuss alternative hypotheses of reptantian interrelationships, the syStematic position of the Reptantia within the decapods, and draw some conclusions concerning the habits and appearance of the reptantian Stem Species.

Martin Heß - One of the best experts on this subject based on the ideXlab platform.

  • Interactive 3D anatomy and affinities of the Hyalogyrinidae, basal Heterobranchia (Gastropoda) with a rhipidoglossate radula
    Organisms Diversity & Evolution, 2011
    Co-Authors: Gerhard Haszprunar, Erika Speimann, Andreas Hawe, Martin Heß
    Abstract:

    Whereas Hyalogyrina Marshall, 1988 was originally considered a skeneid vetigastropod, the family Hyalogyrinidae Warén & Bouchet, 1993 has later been classified as basal Heterobranchia despite their rhipidoglossate radula. In order to evaluate this placement and to shed more light on the origin of all higher Gastropoda, we investigated five representatives of all three nominal hyalogyrinid genera by means of semithin serial sectioning and computer-aided 3D reconstruction of the respective anatomy, which we present in an interactive way. In general the morphological features (shell, external morphology, anatomy) fully confirm the placement of Hyalogyrinidae in the Heterobranchia, but in particular the conditions of the genital syStem vary substantially within the family. The ectobranch gill of Hyalogyrinidae is shared with Valvatidae, Cornirostridae, and Xylodisculidae; consequently all these families are united in Ectobranchia Fischer, 1884. The rhipidoglossate hyalogyrinid radula suggests independent acquisition of taenioglossate radulae in the Caenogastropoda and other Ectobranchia. Therefore, the origin of the Heterobranchia—and thus of all higher gastropods—looks to have taken place already on the rhipidoglossate, i.e. the ‘archaeogastropod’, level of evolution. Ectobranchia are considered the first extant offshoot of the Heterobranchia; implications for the Stem Species of the latter are outlined.

  • Interactive 3D anatomy and affinities of the Hyalogyrinidae, basal Heterobranchia (Gastropoda) with a rhipidoglossate radula
    Organisms Diversity & Evolution, 2011
    Co-Authors: Gerhard Haszprunar, Erika Speimann, Andreas Hawe, Martin Heß
    Abstract:

    Whereas Hyalogyrina Marshall, 1988 was originally considered a skeneid vetigastropod, the family Hyalogyrinidae Waren & Bouchet, 1993 has later been classified as basal Heterobranchia despite their rhipidoglossate radula. In order to evaluate this placement and to shed more light on the origin of all higher Gastropoda, we investigated five representatives of all three nominal hyalogyrinid genera by means of semithin serial sectioning and computer-aided 3D reconstruction of the respective anatomy, which we present in an interactive way. In general the morphological features (shell, external morphology, anatomy) fully confirm the placement of Hyalogyrinidae in the Heterobranchia, but in particular the conditions of the genital syStem vary substantially within the family. The ectobranch gill of Hyalogyrinidae is shared with Valvatidae, Cornirostridae, and Xylodisculidae; consequently all these families are united in Ectobranchia Fischer, 1884. The rhipidoglossate hyalogyrinid radula suggests independent acquisition of taenioglossate radulae in the Caenogastropoda and other Ectobranchia. Therefore, the origin of the Heterobranchia—and thus of all higher gastropods—looks to have taken place already on the rhipidoglossate, i.e. the ‘archaeogastropod’, level of evolution. Ectobranchia are considered the first extant offshoot of the Heterobranchia; implications for the Stem Species of the latter are outlined.

Gerhard Scholtz - One of the best experts on this subject based on the ideXlab platform.

  • Phylogeny of the Anomala (Crustacea, Decapoda, Reptantia) based on the ossicles of the foregut
    Zoologischer Anzeiger – A Journal of Comparative Zoology, 2011
    Co-Authors: André Reimann, Stefan Richter, Gerhard Scholtz
    Abstract:

    We present a cladistic analysis of the Anomala based on 66 ingroup Species and 5 outgroup representatives. Based on a comparative analysis of the morphology of the foregut we scored 124 characters related to size, shape, and fusion of foregut ossicles and other foregut structures. Our parsimony analysis resulted in 30 equally parsimonious trees which differ mainly at the lower hierarchical level. Our study reveals two large clades within Anomala. One large clade consists of Galatheoidea and Chirostyloidea. The internal relationships show a monophyletic Porcellanidae nested within a group comprising paraphyletic Galatheidae, and Munididae as well as Munidopsidae. The other large clade contains Aegla as sister group to a monophyletic group consisting of the Hippoidea and a clade formed by Lomis and the Paguroidea. Coenobitidae are nested within paraphyletic Diogenidae and Lithodidae are nested within paraphyletic Paguridae. The results are discussed in the context of other morphological and molecular analyses. Furthermore, some aspects of carcinization are touched upon; in particular, an anomalan Stem Species with a, at least to some extent, ventrally folded pleon is suggested.

  • Regular articlePhylogenetic syStematics of the reptantian Decapoda (Crustacea, Malacostraca)
    Zoological Journal of the Linnean Society, 1995
    Co-Authors: Gerhard Scholtz, Stefan Richter
    Abstract:

    Although the biology of the reptantian Decapoda has been much studied, the last comprehensive review of reptantian syStematics was published more than 80 years ago. We have used cladistic methods to reconstruct the phylogenetic syStem of the reptantian Decapoda. We can show that the Reptantia represent a monophyletic taxon. The classical groups, the ‘Palinura’, ‘Astacura’ and ‘Anomura’ are paraphyletic assemblages. The Polychelida is the sister-group of all other reptantians. The Astacida is not closely related to the Homarida, but is part of a large monophyletic taxon which also includes the Thalassinida, Anomala and Brachyura. The Anomala and Brachyura are sister-groups and the Thalassinida is the sister-group of both of them. Based on our reconstruction of the sister-group relationships within the Reptantia, we discuss alternative hypotheses of reptantian interrelationships, the syStematic position of the Reptantia within the decapods, and draw some conclusions concerning the habits and appearance of the reptantian Stem Species.

  • Phylogenetic syStematics of the reptantian Decapoda (Crustacea, Malacostraca)
    Zoological Journal of the Linnean Society, 1995
    Co-Authors: Gerhard Scholtz, Stefan Richter
    Abstract:

    Although the biology of the reptantian Decapoda has been much studied, the last comprehensive review of reptantian syStematics was published more than 80 years ago. We have used cladistic methods to reconstruct the phylogenetic syStem of the reptantian Decapoda. We can show that the Reptantia represent a monophyletic taxon. The classical groups, the ‘Palinura’, ‘Astacura’ and ‘Anomura’ are paraphyletic assemblages. The Polychelida is the sister-group of all other reptantians. The Astacida is not closely related to the Homarida, but is part of a large monophyletic taxon which also includes the Thalassinida, Anomala and Brachyura. The Anomala and Brachyura are sister-groups and the Thalassinida is the sister-group of both of them. Based on our reconstruction of the sister-group relationships within the Reptantia, we discuss alternative hypotheses of reptantian interrelationships, the syStematic position of the Reptantia within the decapods, and draw some conclusions concerning the habits and appearance of the reptantian Stem Species.