Developmental Characters Research Articles

An Ordovician vertebrate from western New South Wales, with comments on Cambro-Ordovician vertebrate distribution patterns

Young, G.C., March, 2009. An Ordovician vertebrate from western New South Wales, with comments on Cambro-Ordovician vertebrate distribution patterns. Alcheringa 33, 79–89. ISSN 0311-5518. A fish plate impression from the Ordovician Rowena Formation in Mutawintji National Park is referred to an indeterminate species of the genus Arandaspis Ritchie & Gilbert-Tomlinson, 1977, genotype of the family Arandaspididae, previously known only from the Middle Ordovician Stairway Sandstone in the Amadeus Basin of central Australia. The Rowena Formation has previously been correlated with units underlying the Stairway Sandstone (Pacoota Sandstone, Horn Valley Siltstone) in the Amadeus Basin, from which a second arandaspid Porophoraspis represents the earliest occurrence in the fossil record that demonstrates two defining developmental characters of the vertebrates (neural crest, epidermal placodes). The new occurrence of Arandaspis is consistent with the Middle Ordovician (Darriwilian) age for the upper part of the Rowena Formation indicated by recent studies of trilobites. The order Arandaspidiformes, also known from the Upper Ordovician of South America (Sacabambaspis), defines a ‘Gondwana Endemic Assemblage’, which may have been established already by the late Cambrian. Although the first phase of vertebrate biomineralization is not yet documented from the Cambro-Ordovician of Asia, the oldest vertebrates in the early Cambrian Chengjiang fauna and diverse agnathans and gnathostomes by Early Silurian time in South China implicate this as a significant area in the evolution of the earliest vertebrates.

Research on Corporate Image Orientation

Corporate image orientation is the base of corporate image planning and the first step to implement CIS (Corporate Identify System) designing. According to different schemes and design aims, strategies adopted by corporate image orientation are different. Generally speaking, we can adopt demand adaptation, reciprocal thinking, dominance prominence, reorientation and improving the occasions to implement corporate image orientation. According to their own developmental characters, situations in the market, situations of market competition, enterprises can flexibly adopt corresponding strategies in different stages of enterprise development to make the corporate image orientation clear and exact and make the corporate image impressive.

Les premiers vertébrés et les premières étapes de l’évolution du crâne

The earliest vertebrates and the first steps of the evolution of the skull. Vertebrates are one of the few metazoan taxa, which display a well-corroborated phylogenetic pattern, a good and anatomically informative fossil record, and a relatively slow ontogenetic development. They are thus a favourite taxon for illustrating evolution as a historical process, although the stem of the vertebrate tree remains poorly documented by fossils, except for some Early Cambrian forms. Therefore, the characterization of the vertebrates now rests essentially on a small number of developmental characters, mostly involved in the rise of the skull, and whose precursors may occur in other chordates. The tree of the crown-group vertebrates also shows some major morphological gaps due to early extinctions, but a number of Palaeozoic stem gnathostome taxa helps in documenting the agnathan-gnathostome evolutionary transition. However, stem cyclostomes remain elusive.

The Apicomplexan whole-genome phylogeny: an analysis of incongruence among gene trees.

The protistan phylum Apicomplexa contains many important pathogens and is the subject of intense genome sequencing efforts. Based upon the genome sequences from seven apicomplexan species and a ciliate outgroup, we identified 268 single-copy genes suitable for phylogenetic inference. Both concatenation and consensus approaches inferred the same species tree topology. This topology is consistent with most prior conceptions of apicomplexan evolution based upon ultrastructural and developmental characters, that is, the piroplasm genera Theileria and Babesia form the sister group to the Plasmodium species, the coccidian genera Eimeria and Toxoplasma are monophyletic and are the sister group to the Plasmodium species and piroplasm genera, and Cryptosporidium forms the sister group to the above mentioned with the ciliate Tetrahymena as the outgroup. The level of incongruence among gene trees appears to be high at first glance; only 19% of the genes support the species tree, and a total of 48 different gene-tree topologies are observed. Detailed investigations suggest that the low signal-to-noise ratio in many genes may be the main source of incongruence. The probability of being consistent with the species tree increases as a function of the minimum bootstrap support observed at tree nodes for a given gene tree. Moreover, gene sequences that generate high bootstrap support are robust to the changes in alignment parameters or phylogenetic method used. However, caution should be taken in that some genes can infer a “wrong” tree with strong support because of paralogy, model violations, or other causes. The importance of examining multiple, unlinked genes that possess a strong phylogenetic signal cannot be overstated.

Response of Reproductive Characters of Drought Resistant Peanut Genotypes to Drought

The aims of this study were to evaluate genetic variations in yield and reproductive developmental characters among peanut genotypes in response to drought and relate these responses to pod yield under different soil moisture. Eleven peanut genotypes were tested under three soil moisture levels [field capacity (FC), 2/3 available soil water (AW) and 1/3AW] in field experiments. Data were recorded for number of flowers, pegs (RSs), immature pods and mature pods per plant, seed per pod, 100-seed weight and pod yield at harvest. A drought tolerance index (DTI) for pod yield was calculated as the ratio of pod yield under stress treatment to that under well-watered conditions. The differences among water regimes were significant for pod yield, number of RSs, immature pods and mature pods per plant, seed per pod and 100 seed weight and differences among genotypes were significant for all traits. Drought reduced pod yield, number of RSs, pods and mature pods per plant. Early peak of flowering is important for the formation of mature pods under drought conditions. Two different strategies were used in maintaining high pod yield under drought. High yield potential was important for ICGV 98348 and ICGV 98353, whereas low pod yield reduction was important for ICGV 98305, ICGV 98303 and ICGV 98300. Tifton 8 showed the lowest pod yield and poor seed filling. High RSs and well-filled mature pods were the most important traits contributing to high pod yield in drought resistant genotypes.

Historical biogeography and speciation in the reef fish genus Haemulon (Teleostei: Haemulidae)

The high biodiversity of tropical marine hotspots has long intrigued evolutionary biologists and biogeographers. The genus Haemulon (grunts) is one of the most important (numerically, ecologically, and economically) reef fish groups in the New World and an excellent candidate to test hypotheses of speciation and diversity generation in the Greater Caribbean, the richest Atlantic biodiversity hotspot, as well as the eastern Pacific. To elucidate the phylogenetic relationships among the species of Haemulon, we obtained a combined total of 2639 base pairs from two mitochondrial genes (cytochrome b and cytochrome oxidase I), and two nuclear genes (TMO-4C4 and RAG2) from all nominal species. Parsimony, Maximum likelihood, and Bayesian analyses resulted in a well-resolved phylogeny with almost identical topologies. Previous phylogenetic hypotheses based on adult morphology, such as the close relationship among H. aurolineatum, H. boschmae, and H. striatum were not supported, whereas others using developmental characters, such as the relationship between H. plumieri and H. sciurus, were confirmed. Our data also indicate that the populations of the nominal H. steindachneri from the two sides of the Isthmus of Panama are genetically divergent at the species level in each ocean, and that the boga, Inermia vittata (family Inermiidae), belongs in the genus Haemulon. This evidence implies that there are 21 valid species of Haemulon, two more than previously recognized. The Amazon barrier and the Isthmus of Panama seem to have played roles in allopatric speciation of Haemulon. However, the majority of sister species pairs have completely overlapping distributions, indicating that vicariance is not the only process driving speciation in this genus. We conclude that both vicariance between biogeographic provinces, and ecological mechanisms of speciation within provinces contribute to species richness in the genus Haemulon.

Acoel development supports a simple planula-like urbilaterian.

Molecular approaches to the study of development and evolution have had profound effects on our understanding of the nature of the evolutionary process. Developmental biologists became intoxicated with fanciful notions of reconstructing genetic pathways of morphogenesis while evolutionary biologists were sobered by the fallacy of reconstructing organismal relationships along increasing grades of morphological complexity. Increased taxon sampling and improvements in analytical techniques are providing a new approach and are forcing biologists to move past historical biases to allow more accurate mapping of morphological and developmental characters through evolutionary time. Here, we discuss the possible developmental and morphological features of the 'urbilaterian', the triploblastic animal with anterior-posterior and dorsoventral axes and predecessor of the protostome-deuterostome ancestor. We argue that this animal, with features resembling acoelomorph flatworms, was far simpler morphologically than the protostome-deuterostome ancestor despite possessing a nearly complete eubilaterian genome. We show that the deployment of some genes expected to pattern the protostome-deuterostome ancestor is not deployed in acoels in the predicted manner and thus might have been co-opted after the evolution of the urbilaterian. We also identify the developmental changes related to gastrulation that gave rise to the urbilaterian from a simpler cnidarian-like ancestor.

Evolution of dark-spored Myxomycetes (slime-molds): Molecules versus morphology

The Myxomycetes are a major component of soil amoebae, displaying a complex life cycle that terminates in the formation of often macroscopic fruiting bodies. The classification of Myxomycetes is controversial and strongly depends on the weight given by different authors to morphological and developmental characters. We used a molecular approach to establish the phylogenetic relationships in the dark-spored orders Stemonitales and Physarales. Twenty-five small subunit ribosomal RNA gene sequences were obtained, with focus on two Stemonitales genera, Lamproderma and Comatricha. Unexpectedly, our results show that Stemonitales are paraphyletic with Physarales arising from within a Lamproderma clade. The genus Lamproderma itself is polyphyletic and can be divided into two distinct clades. Additionally, we found that Comatricha nigricapillitia comprises two cryptic species, both related to Enerthenema. Our study allows the reappraisal of morphological and developmental characters in the light of molecular data and sets foundations for a new classification of Myxomycetes.

Inflorescence diversification in the “finger millet clade” (Chloridoideae, Poaceae): a comparison of molecular phylogeny and developmental morphology

Within the Poaceae, inflorescence diversification and its bearing on phylogeny and evolution are exceedingly complex. We used phylogenetic information of the "finger millet clade," a group of grasses with digitate inflorescences, to study the inflorescence diversification. This clade appears monophyletic in the morphological and molecular phylogenetic analyses. Three well-supported clades are shown in our cpDNA-derived phylogeny, with clades I and III consisting of species of Chloris and Microchloa, respectively, and clade II including species of Cynodon, Dactyloctenium, and Eleusine. Variation appears at different times throughout development. Changes involving primordium number and arrangement occur very early, changes involving duration of primordium activity occur much later. Characters derived from the comparison of developmental sequences were optimized onto the most parsimonious tree. The developmental characters were congruent with the molecular phylogeny. Two developmental characters may not be homologous in the Chloris subclade and the Cynodon subclade.

Pollen ontogeny in Brasenia (Cabombaceae, Nymphaeales)

Brasenia is a monotypic genus sporadically distributed throughout the Americas, Asia, Australia, and Africa. It is one of eight genera that comprise the two families of Nymphaeales, or water lilies: Cabombaceae (Brasenia, Cabomba) and Nymphaeaceae (Victoria, Euryale, Nymphaea, Ondinea, Barclaya, Nuphar). Evidence from a range of studies indicates that Nymphaeales are among the most primitive angiosperms. Despite their phylogenetic utility, pollen developmental characters are not well known in Brasenia. This paper is the first to describe the complete pollen developmental sequence in Brasenia schreberi. Anthers at the microspore mother cell, tetrad, free microspore, and mature pollen grain stages were studied using combined scanning electron, transmission electron, and light microscopy. Both tetragonal and decussate tetrads have been identified in Brasenia, indicating successive microsporogenesis. The exine is tectate-columellate. The tetrad stage proceeds rapidly, and the infratectal columellae are the first exine elements to form. Development of the tectum and the foot layer is initiated later during the tetrad stage, with the tectum forming discontinuously. The endexine lamellae form during the free microspore stage, and their development varies in the apertural and non-apertural regions of the pollen wall. Degradation of the secretory tapetum also occurs during the free microspore stage. Unlike other water lilies, Brasenia is wind-pollinated, and several pollen characters appear to be correlated with this pollination syndrome. The adaptive significance of these characters, in contrast to those of the fly-pollinated genus Cabomba, has been considered. Brasenia does not produce pollenkitt nor develop tectal microchannels as does Cabomba. Instead, the discontinuity of the tectum reduces the amount of sporopollenin in the wall, which may allow for more effective wind dispersal. The importance of reassessing palynological characters in light of new ontogenetic data and the phylogenetic implications of this reevaluation are also discussed.

Daya Hasil Sepuluh Galur Introgresi Kacang Tanah Hasil Silangan antara Arachis cardenasii dan A. hypogaea

Diploid species of peanut ( Arachis cardenasii ) showed no symptoms of PStV infection when mechanically inoculated with PStV. Some introgression lines derived from A. cardenasii and A. hypogaea hybridization have been introduced to Indonesia. Evaluation of their adaptability and yield potential were necessary before pursuing further utilization of these introgression lines. The objectives of this research were to determine yield potential of the introgression lines of peanut in green house and field conditions and to evaluate incidence of PStV infection in the field. Peanut plants were grown in the green house and in the field according to standard procedures for raising peanut. Results of the experiments showed that growth and developmental characters of the tested lines were similar between field and green house grown plants. The introgression lines generally exhibited higher secondary branches and longer to flower and harvest as compared to peanut cv. Gajah and Kelinci. The NC-CS30 line was identfied as having higher yield and bigger seed size as compared to standard peanut cultivars (Gajah and Kelinci). Therefore, NC-CS30 germplasm may be further developed as commercial peanut cultivar or be used as donor for peanut breeding in Indonesia.

The embryonic moult in diplogastrids (Nematoda) – homology of developmental stages and heterochrony as a prerequisite for morphological diversity

Video analysis of developing eggs showed that diplogastrids, in contrast to the majority of nematodes, moult from J1 to J2 before they hatch from the egg. This embryonic moult leads to a conflict between the terminology for the J1–J4 postembryonic stages and the definition for the embryonic period that ranges from fertilization to hatching. The nature of developmental stages is discussed on the occasion of this terminological problem. Stages as “embryo”, J1, J2,… are defined as periods of time between certain developmental events and are called instars, whereas other stages as “tadpole stage” refer to characters. Character-defined stages refer to the temporal aspect of developmental characters. Only character-defined stages can be homologized between species. It is proposed to ignore the conflict of the J1–J4 terminology with the embryonic–postembryonic dichotomy as an embryonic stage cannot be satisfyingly defined. The biological relevance of the heterochronic shift of the first moult into the egg period is the possibility to omit secretion of the J1 stoma and pharynx cuticle as the diplogastrid J1 does not feed. Thereby the time slot for stoma morphogenesis that must be finished before cuticle deposition is prolonged. Within Diplogastridae this time slot facilitated the evolution of a tremendous diversity of complex stoma morphologies that is unique within “Rhabditida”.

Development, phylogeny, and taxonomy of Bostrycapulus (Caenogastropoda: Calyptraeidae), an ancient cryptic radiation

Calyptraeid gastropods are well know for the taxonomic difficulties caused by their simple, phenotypically variable shells. In this paper I demonstrate that what was previously considered to be a single species, Crepidula aculeata, is an ancient (3–15 Myr) cryptic species complex made up of at least eight species, and that this group should be placed in the genus Bostrycapulus. Despite the difficulty in finding diagnostic adult shell and anatomical features upon which species can be unambiguously identified, DNA sequences, protoconch morphology, embryonic morphology and developmental characters clearly differentiate these eight species. A single species with direct development and nurse eggs is present in the South Atlantic, and a species with planktotrophic development occurs in the equatorial Pacific. The species from Japan, Australia, Florida, the Pacific coasts of Mexico and Central America, and the Cape Verde Islands all have direct development. Most of these species are separated by > 15% divergence in COI sequence data. The fossil record of Bostrycapulus goes back to the Miocene, which agrees with genetic estimates of divergences within the genus ranging from 3 to 15 Mya. Surprisingly, these ancient species differ only slightly in morphology from each other and genetic differentiation does not correlate with geographical distance. I revise the genus Bostrycapulus on the basis of differences in adult morphology, embryonic morphology, mode of development, protoconch morphology, and DNA sequence data. I also describe four new species (B. pritzkeri sp. nov., B. odites sp. nov., B. latebrus sp. nov. and B. urraca sp. nov.) and remove three others (B. gravispinosus, B. calyptraeformis, and B. cf. tegulicius) from synonymy with B. aculeatus. © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 144, 75−101.

Higher‐Order Phylogeny of Plasmodial Slime Molds (Myxogastria) Based on Elongation Factor 1‐A and Small Subunit rRNA Gene Sequences

The Myxogastria are common soil microorganisms with a life cycle comprised of a plasmodial trophic stage and large fruiting bodies generally visible with the unaided eye. Until now, their classification has been based exclusively on a combination of morphological, ultrastructural, and developmental characters. Our study is the first attempt to examine phylogenetic relationships among these taxa using molecular data. Partial small-subunit ribosomal RNA and/or elongation factor 1-alpha gene sequences were obtained from eleven, mostly field-collected species representing the five orders of Myxogastria. Nineteen sequences were obtained and subjected to phylogenetic analysis together with 10 sequences available from GenBank. Separate and combined analyses of the two data sets support the division of Myxogastria into three distinct groups. The most basal clade consists of the Echinosteliales, an order considered to have affinities with Protostelia. The three species examined possess unpigmented or slightly pigmented spores. The second group consists of Liceales and Trichiales, taxa characterized by the presence of clear, but pigmented, spores. The third group consists of the two remaining orders, Physarales and Stemonitales, both possessing dark spores. This suggests that spore pigmentation is an evolutionarily conservative character in myxogastrians, and that the simple morphology of echinostelids is not a derived feature.

Yield Potential of Ten Peanut Introgression Lines derived from Crosses between Arachis cardenassii and A. hypogaea

Diploid species of peanut (Arachis cardenasii) showed no symptoms of PStV infection when mechanically inoculated with PStV. Some introgression lines derived from A. cardenasii and A. hypogaea hybridization have been introduced to Indonesia. Evaluation of their adaptability and yield potential were necessary before pursuing further utilization of these introgression lines. The objectives of this research were to determine yield potential of the introgression lines of peanut in green house and field conditions and to evaluate incidence of PStV infection in the field. Peanut plants were grown in the green house and in the field according to standard procedures for raising peanut. Results of the experiments showed that growth and developmental characters of the tested lines were similar between field and green house grown plants. The introgression lines generally exhibited higher secondary branches and longer to flower and harvest as compared to peanut cv. Gajah and Kelinci. The NC-CS30 line was identfied as having higher yield and bigger seed size as compared to standard peanut cultivars (Gajah and Kelinci). Therefore, NC-CS30 germplasm may be further developed as commercial peanut cultivar or be used as donor for peanut breeding in Indonesia.

Paper floras: how long will they last? a review of FLOWERING PLANTS OF THE NEOTROPICS

Paper floras: how long will they last? a review of FLOWERING PLANTS OF THE NEOTROPICS

Floral development in Polygala myrtifolia (Polygalaceae) and its similarities with Leguminosae

Floral development of Polygala myrtifolia was studied by the use of SEM, and compared with floral development in Leguminosae, with which Polygalaceae is grouped in Fabales. Five sepals and petals are formed in a helix, the direction of which is predetermined by the sequentially formed bracteoles. The two lateral sepals are delayed in their development, and the two lateral petals are suppressed early. For stamen initiation a hypothetical pathway is presented, in which the initiation is in two helical whorls. The abaxial, antesepalous stamen and the adaxial, antepetalous stamen are lost. In the gynoecium the late closure is distinct. Although the floral morphology of Polygalaceae and Leguminosae differs clearly, the two families do share some developmental features: (1) The formation of a racemose inflorescence, (2) the acropetal and helical initiation of floral organs, (3) the morphogenetic function of bracteoles, (4) the suppression and loss of organs, (5) the synchronous stamen differentiation (after asynchronous initiation) and late fusion of filaments, (6) the late closure of the gynoecium, and (7) the late expression of floral asymmetry. On the basis of these developmental similarities, the placement of Polygalaceae in Fabales becomes more plausible. Further insights in floral evolution of Fabales will be possible by means of a detailed phylogenetic analysis of developmental characters, based on a broadened data matrix.

Genera in the family Agaricaceae: evidence from nrITS and nrLSU sequences

The circumscription of the family Agaricaceae, its genera and their characters are investigated. Analyses of the ITS and LSU sequence data, separately and in combination result in exclusions and reorganization. Notholepiota areolata, a secotioid species from New Zealand, Cystoagaricus with brown, irregular-knobby spores, and Leucopholiota with gelatinized hymenophoral trama and amyloid spores, fall outside the family Agaricaceae. In the reorganization, long accepted tribe and genus definitions are amended, viz.: (1) Macrolepiota and Chlorophyllum separately are monophyletic, but not together; (2) Leucoagaricus and Leucocoprinus together form one large monophyletic clade, that also includes polyphyletic Sericeomyces; (3) Lepiota, Cystolepiota and Melanophyllum together form a monophyletic clade; (4) Secotiation has happened within several clades (e.g. Agaricus and Chlorophyllum), though not in the Leucoagaricus/Leucocoprinus clade, nor in the lineage of Macrolepiota proper; gasteroid and most secotioid species in the course of adaptation acquire coloured spores; and (5) the monovelangiocarpic Chamaemyces fracidus appears to be basal to the family and provides clues to the morphology of the ancestral Agaricaceae. Trama and developmental characters characterize the different clades, whereas spore characters play a minor role.

Morphological and anatomical development in the Vitaceae. VII. Floral development in Rhoicissus digitata with respect to other genera in the family

This study forms part of our series of investigations on genera in the Vitaceae and is the first developmental study for the genus Rhoicissus. Vegetative and reproductive development of shoot apices of Rhoicissus digitata (L.f.) Gilg et Brandt were examined using epi-illumination light microscopy and scanning electron microscopy. Leaf-opposed tendrils or inflorescences, typical of the shoot architecture in the Vitaceae, were present at every node. Macroscopically, the shoot appears to grow either monopodially or sympodially. At the microscopic level, however, shoot development is sympodial; the shoot apical meristem bifurcates unequally, with the larger portion forming an uncommitted primordium, which will become either an inflorescence or a tendril, and the smaller portion (in the position of the axillary bud) forming the new shoot apical meristem. Floral primordia first initiate three sepals followed by a calyx ring on which the last two sepal primordia form. The five petals are initiated in a whorl followed by the five stamens in a petal-opposed position. There is no evidence of a common petal-stamen primordium in this species. The gy noecium is initiated as a ring primordium. Subsequently, the four ovules are initiated at the base of the two septa that grow out from the inner gynoecial wall. The nectary disc forms as an outgrowth of the gynoecium base. Mature flowers have greenish petals and a red nectariferous disc. Flowers are bisexual, and seed germination is approximately 63%. Unlike previous studies in Vitis and Parthenocissus, Rhoicissus appears to have few putatively derived floral developmental characters, which would support its relatively basal position in current phylogenies for the family.Key words: Vitaceae, morphology, development, shoot architecture, flower.

Vertebrate characters and the Cambrian vertebrates

The question of the developmental characters which conventionally define the vertebrates, neural crests and epidermal placodes, and their indirect identification in the fossil material is briefly discussed. Comments are made upon some presumed Cambrian vertebrate or vertebrate-related taxa, with particular reference to the most likely Cambrian vertebrates, Haikouichthys and Myllokunmingia. To cite this article: Ph. Janvier, C. R. Palevol 2 (2003).