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1

Characterization of the stem cell system of the acoel Isodiametra pulchra  

PubMed Central

Background Tissue plasticity and a substantial regeneration capacity based on stem cells are the hallmark of several invertebrate groups such as sponges, cnidarians and Platyhelminthes. Traditionally, Acoela were seen as an early branching clade within the Platyhelminthes, but became recently positioned at the base of the Bilateria. However, little is known on how the stem cell system in this new phylum is organized. In this study, we wanted to examine if Acoela possess a neoblast-like stem cell system that is responsible for development, growth, homeostasis and regeneration. Results We established enduring laboratory cultures of the acoel Isodiametra pulchra (Acoela, Acoelomorpha) and implemented in situ hybridization and RNA interference (RNAi) for this species. We used BrdU labelling, morphology, ultrastructure and molecular tools to illuminate the morphology, distribution and plasticity of acoel stem cells under different developmental conditions. We demonstrate that neoblasts are the only proliferating cells which are solely mesodermally located within the organism. By means of in situ hybridisation and protein localisation we could demonstrate that the piwi-like gene ipiwi1 is expressed in testes, ovaries as well as in a subpopulation of somatic stem cells. In addition, we show that germ cell progenitors are present in freshly hatched worms, suggesting an embryonic formation of the germline. We identified a potent stem cell system that is responsible for development, homeostasis, regeneration and regrowth upon starvation. Conclusions We introduce the acoel Isodiametra pulchra as potential new model organism, suitable to address developmental questions in this understudied phylum. We show that neoblasts in I. pulchra are crucial for tissue homeostasis, development and regeneration. Notably, epidermal cells were found to be renewed exclusively from parenchymally located stem cells, a situation known only from rhabditophoran flatworms so far. For further comparison, it will be important to analyse the stem cell systems of other key-positioned understudied taxa. PMID:20017953

2009-01-01

2

Mesodermal Gene Expression in the Acoel Isodiametra pulchra Indicates a Low Number of Mesodermal Cell Types and the Endomesodermal Origin of the Gonads  

PubMed Central

Acoelomorphs are bilaterally symmetric small marine worms that lack a coelom and possess a digestive system with a single opening. Two alternative phylogenetic positions of this group within the animal tree are currently debated. In one view, Acoelomorpha is the sister group to all remaining Bilateria and as such, is a morphologically simple stepping stone in bilaterian evolution. In the other, the group is a lineage within the Deuterostomia, and therefore, has derived a simple morphology from a more complex ancestor. Acoels and the closely related Nemertodermatida and Xenoturbellida, which together form the Acoelomorpha, possess a very limited number of cell types. To further investigate the diversity and origin of mesodermal cell types we describe the expression pattern of 12 orthologs of bilaterian mesodermal markers including Six1/2, Twist, FoxC, GATA4/5/6, in the acoel Isodiametra pulchra. All the genes are expressed in stem cells (neoblasts), gonads, and at least subsets of the acoel musculature. Most are expressed in endomesodermal compartments of I. pulchra developing embryos similar to what has been described in cnidarians. Our molecular evidence indicates a very limited number of mesodermal cell types and suggests an endomesodermal origin of the gonads and the stem cell system. We discuss our results in light of the two prevailing phylogenetic positions of Acoelomorpha. PMID:23405161

Chiodin, Marta; Børve, Aina; Berezikov, Eugene; Ladurner, Peter; Martinez, Pedro; Hejnol, Andreas

2013-01-01

3

Posterior regeneration in Isodiametra pulchra (Acoela, Acoelomorpha)  

PubMed Central

Introduction Regeneration is a widespread phenomenon in the animal kingdom, but the capacity to restore damaged or missing tissue varies greatly between different phyla and even within the same phylum. However, the distantly related Acoelomorpha and Platyhelminthes share a strikingly similar stem-cell system and regenerative capacity. Therefore, comparing the underlying mechanisms in these two phyla paves the way for an increased understanding of the evolution of this developmental process. To date, Isodiametra pulchra is the most promising candidate as a model for the Acoelomorpha, as it reproduces steadily under laboratory conditions and is amenable to various techniques, including the silencing of gene expression by RNAi. In order to provide an essential framework for future studies, we report the succession of regeneration events via the use of cytochemical, histological and microscopy techniques, and specify the total number of cells in adult individuals. Results Isodiametra pulchra is not capable of regenerating a new head, but completely restores all posterior structures within 10 days. Following amputation, the wound closes via the contraction of local muscle fibres and an extension of the dorsal epidermis. Subsequently, stem cells and differentiating cells invade the wound area and form a loosely delimited blastema. After two days, the posterior end is re-patterned with the male (and occasionally the female) genital primordium being apparent. Successively, these primordia differentiate into complete copulatory organs. The size of the body and also of the male and female copulatory organs, as well as the distance between the copulatory organs, progressively increase and by nine days copulation is possible. Adult individuals with an average length of 670 ?m consist of approximately 8100 cells. Conclusion Isodiametra pulchra regenerates through a combination of morphallactic and epimorphic processes. Existing structures are “re-modelled” and provide a framework onto which newly differentiating cells are added. Growth proceeds through the intercalary addition of structures, mirroring the embryonic and post-embryonic development of various organ systems. The suitability of Isodiametra pulchra for laboratory techniques, the fact that its transcriptome and genome data will soon be available, as well as its small size and low number of cells, make it a prime candidate subject for research into the cellular mechanisms that underlie regeneration in acoelomorphs. PMID:24160844

2013-01-01

4

Characterization of the stem cell system of the acoel Isodiametra pulchra  

Microsoft Academic Search

BACKGROUND: Tissue plasticity and a substantial regeneration capacity based on stem cells are the hallmark of several invertebrate groups such as sponges, cnidarians and Platyhelminthes. Traditionally, Acoela were seen as an early branching clade within the Platyhelminthes, but became recently positioned at the base of the Bilateria. However, little is known on how the stem cell system in this new

Katrien De Mulder; Georg Kuales; Daniela Pfister; Maxime Willems; Bernhard Egger; Willi Salvenmoser; Marlene Thaler; Anne-Kathrin Gorny; Martina Hrouda; Gaëtan Borgonie; Peter Ladurner

2009-01-01

5

To Be or Not to Be a Flatworm: The Acoel Controversy  

PubMed Central

Since first described, acoels were considered members of the flatworms (Platyhelminthes). However, no clear synapomorphies among the three large flatworm taxa - the Catenulida, the Acoelomorpha and the Rhabditophora - have been characterized to date. Molecular phylogenies, on the other hand, commonly positioned acoels separate from other flatworms. Accordingly, our own multi-locus phylogenetic analysis using 43 genes and 23 animal species places the acoel flatworm Isodiametra pulchra at the base of all Bilateria, distant from other flatworms. By contrast, novel data on the distribution and proliferation of stem cells and the specific mode of epidermal replacement constitute a strong synapomorphy for the Acoela plus the major group of flatworms, the Rhabditophora. The expression of a piwi-like gene not only in gonadal, but also in adult somatic stem cells is another unique feature among bilaterians. These two independent stem-cell-related characters put the Acoela into the Platyhelminthes-Lophotrochozoa clade and account for the most parsimonious evolutionary explanation of epidermal cell renewal in the Bilateria. Most available multigene analyses produce conflicting results regarding the position of the acoels in the tree of life. Given these phylogenomic conflicts and the contradiction of developmental and morphological data with phylogenomic results, the monophyly of the phylum Platyhelminthes and the position of the Acoela remain unresolved. By these data, both the inclusion of Acoela within Platyhelminthes, and their separation from flatworms as basal bilaterians are well-supported alternatives. PMID:19430533

Arendt, Detlev; Borgonie, Gaetan; Funayama, Noriko; Gschwentner, Robert; Hartenstein, Volker; Hobmayer, Bert; Hooge, Matthew; Hrouda, Martina; Ishida, Sachiko; Kobayashi, Chiyoko; Kuales, Georg; Nishimura, Osamu; Pfister, Daniela; Rieger, Reinhard; Salvenmoser, Willi; Smith, Julian; Technau, Ulrich; Tyler, Seth; Agata, Kiyokazu; Salzburger, Walter; Ladurner, Peter

2009-01-01

6

Graptemys pulchra Baur 1893: Alabama Map Turtle  

USGS Publications Warehouse

The Alabama Map Turtle, Graptemys pulchra (Family Emydidae), is a moderately large riverine species endemic to the Mobile Bay drainage system of Alabama, Georgia, and Mississippi. Sexual size dimorphism is pronounced, with adult females (carapace length [CL] to 273 mm) attaining more than twice the size of adult males (CL to 117 mm). The species is an inhabitant of relatively large, swift creeks and rivers, often with wide sandbars. Stream sections open to the sun and with abundant basking sites in the form of logs and brush are preferred. Six to seven clutches of 4–7 eggs are laid each year on river sandbars. Although the species is locally abundant, populations are threatened by habitat destruction, declines in their prey base, commercial collection, and vandalism. It is listed as a Species of Special Concern in Alabama.

Lovich, Jeffrey E.; Godwin, James C.; McCoy, C. J.

2014-01-01

7

Acoel development supports a simple planula-like urbilaterian.  

PubMed

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. PMID:18192185

Hejnol, Andreas; Martindale, Mark Q

2008-04-27

8

Phylogenetic distribution of microRNAs supports the basal position of acoel flatworms and the polyphyly of Platyhelminthes.  

PubMed

Phylogenetic analyses based on gene sequences suggest that acoel flatworms are not members of the phylum Platyhelminthes, but instead are the most basal branch of triploblastic bilaterians. Nonetheless, this result has been called into question. An alternative test is to use qualitative molecular markers that should, in principle, exclude the possibility of convergent (homoplastic) evolution in unrelated groups. microRNAs (miRNAs), noncoding regulatory RNA molecules that are under intense stabilizing selection, are a newly discovered set of phylogenetic markers that can resolve such taxonomic disputes. The acoel Childia sp. has recently been shown to possess a subset of the conserved core of miRNAs found across deuterostomes and protostomes, whereas a polyclad flatworm-in addition to this core subset-possesses miRNAs restricted to just protostomes. Here, we examine another acoel, Symsagittifera roscoffensis, and three other platyhelminths. Our results show that the distribution of miRNAs in S. roscoffensis parallels that of Childia. In addition, two of 13 new miRNAs cloned from a triclad flatworm are also found in other lophotrochozoan protostomes, but not in ecdysozoans, deuterostomes, or in basal metazoans including acoels. The limited set of miRNAs found in acoels, intermediate between the even more reduced set in cnidarians and the larger and expanding set in the rest of bilaterians, is compelling evidence for the basal position of acoel flatworms and the polyphyly of Platyhelminthes. PMID:17845513

Sempere, Lorenzo F; Martinez, Pedro; Cole, Charles; Baguñà, Jaume; Peterson, Kevin J

2007-01-01

9

Centaurea solstitialis Invasion Success Is Influenced by Nassella pulchra Size  

Microsoft Academic Search

Replacement of perennial grasses with non-native annual grasses in California's Central Valley grasslands and foot- hills has increased deep soil water availability. Yellow starthistle (Centaurea solstitialis), a deep-rooted invasive thistle, can use this water to invade annual grasslands. Native perennial bunchgrasses, such as Purple needlegrass (Nassella pulchra), also use deep soil water, so there is an overlap in resource use

Kimberly J. Reever Morghan; Kevin J. Rice

2005-01-01

10

Whole-body acoel regeneration is controlled by Wnt and Bmp-Admp signaling.  

PubMed

Whole-body regeneration is widespread in the Metazoa, yet little is known about how underlying molecular mechanisms compare across phyla. Acoels are an enigmatic phylum of invertebrate worms that can be highly informative about many questions in bilaterian evolution, including regeneration. We developed the three-banded panther worm, Hofstenia miamia, as a new acoelomorph model system for molecular studies of regeneration. Hofstenia were readily cultured, with accessible embryos, juveniles, and adults for experimentation. We developed molecular resources and tools for Hofstenia, including a transcriptome and robust systemic RNAi. We report the identification of molecular mechanisms that promote whole-body regeneration in Hofstenia. Wnt signaling controls regeneration of the anterior-posterior axis, and Bmp-Admp signaling controls regeneration of the dorsal-ventral axis. Perturbation of these pathways resulted in regeneration-abnormal phenotypes involving axial feature duplication, such as the regeneration of two heads following Wnt perturbation or the regeneration of ventral cells in place of dorsal ones following bmp or admp RNAi. Hofstenia regenerative mechanisms are strikingly similar to those guiding regeneration in planarians. However, phylogenetic analyses using the Hofstenia transcriptome support an early branching position for acoels among bilaterians, with the last common ancestor of acoels and planarians being the ancestor of the Bilateria. Therefore, these findings identify similar whole-body regeneration mechanisms in animals separated by more than 550 million years of evolution. PMID:24768051

Srivastava, Mansi; Mazza-Curll, Kathleen L; van Wolfswinkel, Josien C; Reddien, Peter W

2014-05-19

11

Acoel development indicates the independent evolution of the bilaterian mouth and anus.  

PubMed

Most bilaterian animals possess a through gut with a separate mouth and anus. It is commonly believed that during the transition from radial to bilateral symmetry, both openings evolved simultaneously by the lateral closure of a slit-like blastopore. Molecular phylogenies however, place the acoel flatworms, which have only one opening to their digestive system, as the sister group to all remaining Bilateria. To address how this single body opening is related to the mouth and anus of the protostomes and deuterostomes, we studied the expression of genes involved in bilaterian foregut and hindgut patterning during the development of the acoel Convolutriloba longifissura. Here we show that the genes brachyury and goosecoid are expressed in association with the acoel mouth, suggesting that this single opening is homologous to the mouth of other bilaterians. In addition, we find that the genes caudal, orthopedia and brachyury-which are expressed in various bilaterian hindguts-are expressed in a small region at the posterior end of the animal, separated from the anterior oral brachyury-expressing region by a dorsal domain of ectodermal bmp2/4 expression. These results contradict the hypothesis that the bilaterian mouth and anus evolved simultaneously from a common blastoporal opening, and suggest that a through gut might have evolved independently in different animal lineages. PMID:18806777

Hejnol, Andreas; Martindale, Mark Q

2008-11-20

12

The chimerical and multifaceted marine acoel Symsagittifera roscoffensis: from photosymbiosis to brain regeneration.  

PubMed

A remarkable example of biological engineering is the capability of some marine animals to take advantage of photosynthesis by hosting symbiotic algae. This capacity, referred to as photosymbiosis, is based on structural and functional complexes that involve two distantly unrelated organisms. These stable photosymbiotic associations between metazoans and photosynthetic protists play fundamental roles in marine ecology as exemplified by reef communities and their vulnerability to global changes threats. Here we introduce a photosymbiotic tidal acoel flatworm, Symsagittifera roscoffensis, and its obligatory green algal photosymbiont, Tetraselmis convolutae (Lack of the algal partner invariably results in acoel lethality emphasizing the mandatory nature of the photosymbiotic algae for the animal's survival). Together they form a composite photosymbiotic unit, which can be reared in controlled conditions that provide easy access to key life-cycle events ranging from early embryogenesis through the induction of photosymbiosis in aposymbiotic juveniles to the emergence of a functional "solar-powered" mature stage. Since it is possible to grow both algae and host under precisely controlled culture conditions, it is now possible to design a range of new experimental protocols that address the mechanisms and evolution of photosymbiosis. S. roscoffensis thus represents an emerging model system with experimental advantages that complement those of other photosymbiotic species, in particular corals. The basal taxonomic position of S. roscoffensis (and acoels in general) also makes it a relevant model for evolutionary studies of development, stem cell biology and regeneration. Finally, it's autotrophic lifestyle and lack of calcification make S. roscoffensis a favorable system to study the role of symbiosis in the response of marine organisms to climate change (e.g., ocean warming and acidification). In this article we summarize the state of knowledge of the biology of S. roscoffensis and its algal partner from studies dating back over a century, and provide an overview of ongoing research efforts that take advantage of this unique system. PMID:25324833

Bailly, Xavier; Laguerre, Laurent; Correc, Gaëlle; Dupont, Sam; Kurth, Thomas; Pfannkuchen, Anja; Entzeroth, Rolf; Probert, Ian; Vinogradov, Serge; Lechauve, Christophe; Garet-Delmas, Marie-José; Reichert, Heinrich; Hartenstein, Volker

2014-01-01

13

The chimerical and multifaceted marine acoel Symsagittifera roscoffensis: from photosymbiosis to brain regeneration  

PubMed Central

A remarkable example of biological engineering is the capability of some marine animals to take advantage of photosynthesis by hosting symbiotic algae. This capacity, referred to as photosymbiosis, is based on structural and functional complexes that involve two distantly unrelated organisms. These stable photosymbiotic associations between metazoans and photosynthetic protists play fundamental roles in marine ecology as exemplified by reef communities and their vulnerability to global changes threats. Here we introduce a photosymbiotic tidal acoel flatworm, Symsagittifera roscoffensis, and its obligatory green algal photosymbiont, Tetraselmis convolutae (Lack of the algal partner invariably results in acoel lethality emphasizing the mandatory nature of the photosymbiotic algae for the animal's survival). Together they form a composite photosymbiotic unit, which can be reared in controlled conditions that provide easy access to key life-cycle events ranging from early embryogenesis through the induction of photosymbiosis in aposymbiotic juveniles to the emergence of a functional “solar-powered” mature stage. Since it is possible to grow both algae and host under precisely controlled culture conditions, it is now possible to design a range of new experimental protocols that address the mechanisms and evolution of photosymbiosis. S. roscoffensis thus represents an emerging model system with experimental advantages that complement those of other photosymbiotic species, in particular corals. The basal taxonomic position of S. roscoffensis (and acoels in general) also makes it a relevant model for evolutionary studies of development, stem cell biology and regeneration. Finally, it's autotrophic lifestyle and lack of calcification make S. roscoffensis a favorable system to study the role of symbiosis in the response of marine organisms to climate change (e.g., ocean warming and acidification). In this article we summarize the state of knowledge of the biology of S. roscoffensis and its algal partner from studies dating back over a century, and provide an overview of ongoing research efforts that take advantage of this unique system.

Bailly, Xavier; Laguerre, Laurent; Correc, Gaelle; Dupont, Sam; Kurth, Thomas; Pfannkuchen, Anja; Entzeroth, Rolf; Probert, Ian; Vinogradov, Serge; Lechauve, Christophe; Garet-Delmas, Marie-Jose; Reichert, Heinrich; Hartenstein, Volker

2014-01-01

14

Coordinated spatial and temporal expression of Hox genes during embryogenesis in the acoel Convolutriloba longifissura  

PubMed Central

Background Hox genes are critical for patterning the bilaterian anterior-posterior axis. The evolution of their clustered genomic arrangement and ancestral function has been debated since their discovery. As acoels appear to represent the sister group to the remaining Bilateria (Nephrozoa), investigating Hox gene expression will provide an insight into the ancestral features of the Hox genes in metazoan evolution. Results We describe the expression of anterior, central and posterior class Hox genes and the ParaHox ortholog Cdx in the acoel Convolutriloba longifissura. Expression of all three Hox genes begins contemporaneously after gastrulation and then resolves into staggered domains along the anterior-posterior axis, suggesting that the spatial coordination of Hox gene expression was present in the bilaterian ancestor. After early surface ectodermal expression, the anterior and central class genes are expressed in small domains of putative neural precursor cells co-expressing ClSoxB1, suggesting an evolutionary early function of Hox genes in patterning parts of the nervous system. In contrast, the expression of the posterior Hox gene is found in all three germ layers in a much broader posterior region of the embryo. Conclusion Our results suggest that the ancestral set of Hox genes was involved in the anterior-posterior patterning of the nervous system of the last common bilaterian ancestor and were later co-opted for patterning in diverse tissues in the bilaterian radiation. The lack of temporal colinearity of Hox expression in acoels may be due to a loss of genomic clustering in this clade or, alternatively, temporal colinearity may have arisen in conjunction with the expansion of the Hox cluster in the Nephrozoa. PMID:19796382

Hejnol, Andreas; Martindale, Mark Q

2009-01-01

15

Localisation and surface quantification of secondary metabolites in the red alga Delisea pulchra  

Microsoft Academic Search

The localisation of halogenated furanones, the biologically active secondary metabolites from the red alga Delisea pulchra (Greville), was determined by a combination of fluorescence microscopy, culture studies and quantitative chemical analyses.\\u000a All types of evidence showed that furanones are localised in the central vesicle of gland cells in D. pulchra. These cells release furanones onto the surface of the plant,

S. A. Dworjanyn; R. De Nys; P. D. Steinberg

1999-01-01

16

Coordinated spatial and temporal expression of Hox genes during embryogenesis in the acoel Convolutriloba longifissura  

Microsoft Academic Search

Background  \\u000a Hox genes are critical for patterning the bilaterian anterior-posterior axis. The evolution of their clustered genomic arrangement\\u000a and ancestral function has been debated since their discovery. As acoels appear to represent the sister group to the remaining\\u000a Bilateria (Nephrozoa), investigatingHox gene expression will provide an insight into the ancestral features of theHox genes in metazoan evolution.\\u000a \\u000a \\u000a \\u000a \\u000a Results  We describe the

Andreas Hejnol; Mark Q Martindale

2009-01-01

17

Making heads from tails: Development of a reversed anterior–posterior axis during budding in an acoel  

Microsoft Academic Search

The anterior–posterior axis is a key feature of the bilaterian body plan. Although axis specification during embryogenesis has been studied extensively, virtually nothing is known about how this axis can be established post-embryonically, as occurs in budding animals. We investigated bud formation in the acoel Convolutriloba retrogemma, which reproduces by a remarkable process involving the formation of animals with linked

James M. Sikes; Alexandra E. Bely

2010-01-01

18

High genetic diversity among fossorial lizard populations ( Anniella pulchra ) in a rapidly developing landscape (Central California)  

Microsoft Academic Search

California is a biodiversity hotspot facing unbridled human population growth, especially in Central California. One of the\\u000a poorly known, sensitive species in this area is the California legless lizard (Anniella pulchra), a fossorial worm-like reptile. We report mt and nuDNA sequences from 69 museum-vouchered samples of Anniella (A. pulchra and its sister species A. geronimensis) from 48 localities. Our genetic

James F. Parham; Theodore J. Papenfuss

2009-01-01

19

Characterization of 12 microsatellite loci from an enriched genomic library in polyploid Tibouchina pulchra Cogn. (Melastomataceae)  

Microsoft Academic Search

Tibouchina pulchra is a common hermaphroditic canopy tree of the Melastomataceae in the Brazilian Atlantic Rain Forest that is important for\\u000a bee communities, reforestation, soil and air bio-indication and urban ornamentation. Twelve polymorphic microsatellite markers\\u000a were isolated and characterized in 89 genotypes of T. pulchra from two populations of Ubatuba and São Luís do Paraitinga municipalities (São Paulo, Brazil). The

Vinícius L. G. Brito; Bianca B. Z. Vigna; Anete P. de Souza

2010-01-01

20

Chemistry and Antiviral Activity of Arrabidaea pulchra (Bignoniaceae).  

PubMed

The aim of the present work was to carry out a bioguided isolation of antiviral chemical constituents from an ethanol extract of leaves from Arrabidaea pulchra (Cham.) Sandwith (EEAPL) that had shown in vitro activity in a previous screening using DNA and RNA viruses. The activity of EEPAL was evaluated against the DNA viruses Human herpesvirus 1 (HSV-1) and Vaccinia virus Western Reserve (VACV-WR) as well as against the RNA viruses Murine encephalomyocarditis virus (EMCV), and Dengue virus 2 (DENV-2) by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay. Cytotoxicity was determined in LLCMK2 and Vero cells and the Selectivity Indexes (SI) were calculated. The most potent effect was observed against DENV-2 (EC50 46.8 ± 1.6 µg mL(-1); SI 2.7). For HSV-1 and VACV-WR EC50 values > 200 µg mL(-1) were determined, while no inhibition of the cytopathic effect was observed with EMCV. Bioguided fractionation of EEAPL by partition between immiscible solvents followed by chromatography over a Sephadex LH20 column afforded two arylpropanoid glycosides, verbascoside (AP 1) and caffeoylcalleryanin (AP 2), along with a terpenoid, ursolic acid (AP 3). AP 1 and AP 3 exhibited similar anti-DENV-2 profiles, with SI values of 3.8 and 3.1, respectively, while AP 2 was the most effective anti-DENV-2 constituent, with a SI of 20.0. Our results show that A. pulchra leaves ethanol extract (EEAPL) affords compounds with antiviral activity, mainly against DENV-2. PMID:23959197

Brandão, Geraldo Célio; Kroon, Erna G; Souza, Danielle E R; Souza Filho, José D; Oliveira, Alaíde Braga

2013-01-01

21

Broad spectrum effects of secondary metabolites from the red alga delisea pulchra in antifouling assays  

Microsoft Academic Search

In this study the antifouling activity was investigated of a series of chemically related, halogenated furanones isolated from Delisea pulchra (Greville) Montagne, a red alga which is rarely fouled in the field. The metabolites were tested in laboratory assays against representatives of the three major groups of fouling organisms, the barnacle Balanus amphitrite amphitirite Darwin, the macroalga Ulva lactuca Linnaeus

R. De Nys; P. D. Steinberg; P. Willemsen; S. A. Dworjanyn; C. L. Gabelish; R. J. King

1995-01-01

22

Structure of the central nervous system of a juvenile acoel, Symsagittifera roscoffensis  

PubMed Central

The neuroarchitecture of Acoela has been at the center of morphological debates. Some authors, using immunochemical tools, suggest that the nervous system in Acoela is organized as a commissural brain that bears little resemblance to the central, ganglionic type brain of other flatworms, and bilaterians in general. Others, who used histological staining on paraffin sections, conclude that it is a compact structure (an endonal brain; e.g., Raikova 2004; von Graff 1891; Delage Arch Zool Exp Gén 4:109-144, 1886). To address this question with modern tools, we have obtained images from serial transmission electron microscopic sections of the entire hatchling of Symsagittifera roscoffensis. In addition, we obtained data from wholemounts of hatchlings labeled with markers for serotonin and tyrosinated tubulin. Our data show that the central nervous system of a juvenile S. roscoffensis consists of an anterior compact brain, formed by a dense, bilobed mass of neuronal cell bodies surrounding a central neuropile. The neuropile flanks the median statocyst and contains several types of neurites, classified according to their types of synaptic vesicles. The neuropile issues three pairs of nerve cords that run at different dorso-ventral positions along the whole length of the body. Neuronal cell bodies flank the cords, and neuromuscular synapses are abundant. The TEM analysis also reveals different classes of peripheral sensory neurons and provides valuable information about the spatial relationships between neurites and other cell types within the brain and nerve cords. We conclude that the acoel S. roscoffensis has a central brain that is comparable in size and architecture to the brain of other (rhabditophoran) flatworms. PMID:20549514

Cardona, Albert; Martinez, Pedro

2010-01-01

23

Dissociation of Circadian and Circatidal Timekeeping in the Marine Crustacean Eurydice pulchra  

PubMed Central

Summary Background Tidal (12.4 hr) cycles of behavior and physiology adapt intertidal organisms to temporally complex coastal environments, yet their underlying mechanism is unknown. However, the very existence of an independent “circatidal” clock has been disputed, and it has been argued that tidal rhythms arise as a submultiple of a circadian clock, operating in dual oscillators whose outputs are held in antiphase i.e., ?12.4 hr apart. Results We demonstrate that the intertidal crustacean Eurydice pulchra (Leach) exhibits robust tidal cycles of swimming in parallel to circadian (24 hr) rhythms in behavioral, physiological and molecular phenotypes. Importantly, ?12.4 hr cycles of swimming are sustained in constant conditions, they can be entrained by suitable stimuli, and they are temperature compensated, thereby meeting the three criteria that define a biological clock. Unexpectedly, tidal rhythms (like circadian rhythms) are sensitive to pharmacological inhibition of Casein kinase 1, suggesting the possibility of shared clock substrates. However, cloning the canonical circadian genes of E. pulchra to provide molecular markers of circadian timing and also reagents to disrupt it by RNAi revealed that environmental and molecular manipulations that confound circadian timing do not affect tidal timing. Thus, competent circadian timing is neither an inevitable nor necessary element of tidal timekeeping. Conclusions We demonstrate that tidal rhythms are driven by a dedicated circatidal pacemaker that is distinct from the circadian system of E. pulchra, thereby resolving a long-standing debate regarding the nature of the circatidal mechanism. PMID:24076244

Zhang, Lin; Hastings, Michael H.; Green, Edward W.; Tauber, Eran; Sladek, Martin; Webster, Simon G.; Kyriacou, Charalambos P.; Wilcockson, David C.

2013-01-01

24

Protective effect of Millettia pulchra polysaccharide on cognitive impairment induced by D-galactose in mice.  

PubMed

A polysaccharide (PMP) was isolated from Millettia pulchra and purified by DEAE-cellulose and Sephadex G-75 chromatography. The results showed that PMP was composed of d-glucose and d-arabinose in a molar ratio of 90.79% and 9.21%, with an average molecular weight of about 14,301 Da. Furthermore, the effect of PMP on cognitive impairment induced by d-galactose in mice was evaluated. Treatment with PMP significantly reversed d-galactose-induced learning and memory impairments, as measured by behavioral tests. One of the potential mechanisms of this action was to reduce oxidative stress and suppress inflammatory responses. Furthermore, our results also showed that PMP markedly reduced the content and deposition of ?-amyloid peptide, improved the dysfunction of synaptic plasticity, increased the levels of acetylcholine, but decreased cholinesterase activity. These results suggest that PMP exerts an effective protection against d-galactose-induced cognitive impairment, and PMP may be a major bioactive ingredient in M. pulchra. PMID:24299809

Lin, Xing; Huang, Zhongshi; Chen, Xiaoyu; Rong, Yanping; Zhang, Shijun; Jiao, Yang; Huang, Quanfang; Huang, Renbin

2014-01-30

25

Vanadium bromoperoxidase from Delisea pulchra: enzyme-catalyzed formation of bromofuranone and attendant disruption of quorum sensing.  

PubMed

Vanadium bromoperoxidase was isolated and cloned from the marine red alga Delisea pulchra. This enzyme catalyzes the bromolactonization of 4-pentynoic acid forming 5E-bromo-methylidenetetrahydro-2-furanone, a compound which is shown herein to inhibit quorum sensing in the engineered reporter strain, Agrobacterium tumefaciens NTL4. PMID:22006105

Sandy, Moriah; Carter-Franklin, Jayme N; Martin, Jessica D; Butler, Alison

2011-11-28

26

Growth rates, biomass and distribution of selected woody plant roots in Burkea africana-Ochna pulchra savanna  

Microsoft Academic Search

Woody plants in an African Burkea africana-Ochna pulchra savanna on deep sandy soil were found to have characteristically bimorphic root systems. The shallow lateral root component was often well developed and roots extended up to seven times the extent of the plant canopy in several species. Exponential tapering of lateral roots was found in Terminalia sericea. The wide-ranging roots, together

M. C. Rutherford

1983-01-01

27

Community structure and functional gene profile of bacteria on healthy and diseased thalli of the red seaweed Delisea pulchra.  

PubMed

Disease is increasingly viewed as a major factor in the ecology of marine communities and its impact appears to be increasing with environmental change, such as global warming. The temperate macroalga Delisea pulchra bleaches in Southeast Australia during warm summer periods, a phenomenon which previous studies have indicated is caused by a temperature induced bacterial disease. In order to better understand the ecology of this disease, the bacterial communities associated with threes type of samples was investigated using 16S rRNA gene and environmental shotgun sequencing: 1) unbleached (healthy) D. pulchra 2) bleached parts of D. pulchra and 3) apparently healthy tissue adjacent to bleached regions. Phylogenetic differences between healthy and bleached communities mainly reflected relative changes in the taxa Colwelliaceae, Rhodobacteraceae, Thalassomonas and Parvularcula. Comparative metagenomics showed clear difference in the communities of healthy and diseased D. pulchra as reflected by changes in functions associated with transcriptional regulation, cation/multidrug efflux and non-ribosomal peptide synthesis. Importantly, the phylogenetic and functional composition of apparently healthy tissue adjacent to bleached sections of the thalli indicated that changes in the microbial communities already occur in the absence of visible tissue damage. This shift in unbleached sections might be due to the decrease in furanones, algal metabolites which are antagonists of bacterial quorum sensing. This study reveals the complex shift in the community composition associated with bleaching of Delisea pulchra and together with previous studies is consistent with a model in which elevated temperatures reduce levels of chemical defenses in stressed thalli, leading to colonization or proliferation by opportunistic pathogens or scavengers. PMID:23226544

Fernandes, Neil; Steinberg, Peter; Rusch, Doug; Kjelleberg, Staffan; Thomas, Torsten

2012-01-01

28

Community Structure and Functional Gene Profile of Bacteria on Healthy and Diseased Thalli of the Red Seaweed Delisea pulchra  

PubMed Central

Disease is increasingly viewed as a major factor in the ecology of marine communities and its impact appears to be increasing with environmental change, such as global warming. The temperate macroalga Delisea pulchra bleaches in Southeast Australia during warm summer periods, a phenomenon which previous studies have indicated is caused by a temperature induced bacterial disease. In order to better understand the ecology of this disease, the bacterial communities associated with threes type of samples was investigated using 16S rRNA gene and environmental shotgun sequencing: 1) unbleached (healthy) D. pulchra 2) bleached parts of D. pulchra and 3) apparently healthy tissue adjacent to bleached regions. Phylogenetic differences between healthy and bleached communities mainly reflected relative changes in the taxa Colwelliaceae, Rhodobacteraceae, Thalassomonas and Parvularcula. Comparative metagenomics showed clear difference in the communities of healthy and diseased D. pulchra as reflected by changes in functions associated with transcriptional regulation, cation/multidrug efflux and non-ribosomal peptide synthesis. Importantly, the phylogenetic and functional composition of apparently healthy tissue adjacent to bleached sections of the thalli indicated that changes in the microbial communities already occur in the absence of visible tissue damage. This shift in unbleached sections might be due to the decrease in furanones, algal metabolites which are antagonists of bacterial quorum sensing. This study reveals the complex shift in the community composition associated with bleaching of Delisea pulchra and together with previous studies is consistent with a model in which elevated temperatures reduce levels of chemical defenses in stressed thalli, leading to colonization or proliferation by opportunistic pathogens or scavengers. PMID:23226544

Fernandes, Neil; Steinberg, Peter; Rusch, Doug; Kjelleberg, Staffan; Thomas, Torsten

2012-01-01

29

Rapid Development of Microsatellite Markers with 454 Pyrosequencing in a Vulnerable Fish, the Mottled Skate, Raja pulchra  

PubMed Central

The mottled skate, Raja pulchra, is an economically valuable fish. However, due to a severe population decline, it is listed as a vulnerable species by the International Union for Conservation of Nature. To analyze its genetic structure and diversity, microsatellite markers were developed using 454 pyrosequencing. A total of 17,033 reads containing dinucleotide microsatellite repeat units (mean, 487 base pairs) were identified from 453,549 reads. Among 32 loci containing more than nine repeat units, 20 primer sets (62%) produced strong PCR products, of which 14 were polymorphic. In an analysis of 60 individuals from two R. pulchra populations, the number of alleles per locus ranged from 1–10, and the mean allelic richness was 4.7. No linkage disequilibrium was found between any pair of loci, indicating that the markers were independent. The Hardy–Weinberg equilibrium test showed significant deviation in two of the 28 single-loci after sequential Bonferroni’s correction. Using 11 primer sets, cross-species amplification was demonstrated in nine related species from four families within two classes. Among the 11 loci amplified from three other Rajidae family species; three loci were polymorphic. A monomorphic locus was amplified in all three Rajidae family species and the Dasyatidae family. Two Rajidae polymorphic loci amplified monomorphic target DNAs in four species belonging to the Carcharhiniformes class, and another was polymorphic in two Carcharhiniformes species. PMID:22837688

Kang, Jung-Ha; Park, Jung-Youn; Jo, Hyun-Su

2012-01-01

30

Response of stress indicators and growth parameters of Tibouchina pulchra Cogn. exposed to air and soil pollution near the industrial complex of Cubatão, Brazil  

Microsoft Academic Search

The present study was performed in the vicinity of the industrial complex of Cubatão, São Paulo, Brazil, in order to evaluate the response of ‘manaca da serra’ Tibouchina pulchra Cogn. (Melastomataceae), a common species of secondary Atlantic Rain Forest vegetation, to the impact of complex air pollution. Emphasis was given to changes of biochemical parameters such as ascorbic acid concentration,

Gabriele Klumpp; Claudia M. Furlan; Marisa Domingos; Andreas Klumpp

2000-01-01

31

Halogenated furanones from the red alga, Delisea pulchra, inhibit carbapenem antibiotic synthesis and exoenzyme virulence factor production in the phytopathogen Erwinia carotovora  

Microsoft Academic Search

The plant pathogen Erwinia carotovora regulates expression of virulence factors and antibiotic production via an N-3-oxohexanoyl-L-homoserine lactone (3-oxo-C6-HSL) dependent quorum sensing mechanism. The marine alga Delisea pulchra produces halogenated furanones known to antagonise 3-oxo-C6-HSL activity. We have tested the effects of a halogenated furanone on the production of carbapenem, cellulase and protease in E. carotovora. Despite differences in the regulatory

Michael Manefield; Martin Welch; Michael Givskov; George P. C. Salmond; Staffan Kjelleberg

2001-01-01

32

Establishing the redox potential of Tibouchina pulchra (Cham.) Cogn., a native tree species from the Atlantic Rain Forest, in the vicinity of an oil refinery in SE Brazil.  

PubMed

The present study aimed to establish the seasonal variations in the redox potential ranges of young Tibouchina pulchra plants growing in the Cubatão region (SE Brazil) under varying levels of oxidative stress caused by air pollutants. The plants were exposed to filtered air (FA) and non-filtered air (NFA) in open-top chambers installed next to an oil refinery in Cubatão during six exposure periods of 90 days each, which included the winter and summer seasons. After exposure, several analyses were performed, including the foliar concentrations of ascorbic acid and glutathione in its reduced (AsA and GSH), total (totAA and totG) and oxidized forms (DHA and GSSG); their ratios (AsA/totAA and GSH/totG); the enzymatic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR); and the content of malondialdehyde (MDA). The range of antioxidant responses in T. pulchra plants varied seasonally and was stimulated by high or low air pollutant concentrations and/or air temperatures. Glutathione and APX were primarily responsible for increasing plant tolerance to oxidative stress originating from air pollution in the region. The high or low air temperatures mainly affected enzymatic activity. The content of MDA increased in response to increasing ozone concentration, thus indicating that the pro-oxidant/antioxidant balance may not have been reached. PMID:24407781

Esposito, Marisia Pannia; Domingos, Marisa

2014-04-01

33

The redifferentiation of nutritive cells in galls induced by Lepidoptera on Tibouchina pulchra (Cham.) Cogn. reveals predefined patterns of plant development.  

PubMed

Insect galls may present nutritive tissues with distinct cytological features related to the order of the gall inducer. Galling Lepidoptera larvae chew plant cells and induce the redifferentiation of parenchymatic cells into nutritive ones. The nutritive cells in the galls induced by a microlepidoptera on the leaves of Tibouchina pulchra (Cham.) Cogn. (Melastomataceae) are organelle-rich, with developed Golgi apparatus, endoplasmic reticulum, ribosomes, polyribosomes, mitochondria, plastids, and one great central or several fragmented vacuoles. The nonobservance of the nuclei in the nutritive cells deserves special attention, and confers a similarity between the nutritive cells and the vascular conductive ones. The great amount of rough endoplasmic reticulum, ribosomes, polyribosomes, and mitochondria is indicative of the high metabolic status of these cells. They are vascular cambium-like, with high protein synthesis and lipid storage. The proteins are essential to enzymatic metabolism, and secondarily, to larvae nutrition, similarly to the lipid droplets which confer energetic profile to these nutritive cells. The living enucleated cells receive mRNA from their neighbor ones, which may support the high metabolic profile of endoplasmic reticulum and ribosomes observed in galls. Thus, the nutritive cells are stimulated by the galling larvae activity, generating a new cell type, whose redifferentiation includes a mix of intrinsic and common plant pathways. PMID:23779213

Vecchi, Claudia; Menezes, Nanuza Luiza; Oliveira, Denis Coelho; Ferreira, Bruno Garcia; Isaias, Rosy Mary Santos

2013-12-01

34

Physiological responses of the tropical tree Tibouchina pulchra Cogn under the influence of combustion of crude oil and natural gas at an oil refinery.  

PubMed

A refinery located on the slopes of a mountain range in the city of Cubatão (SE-Brazil) is the main source of sulfur dioxide (SO(2)) in the region. For this reason, the refinery replaced a system in which energy was produced from crude oil combustion in boilers with a system of energy and vapor co-generation in a thermoelectric power plant fueled by natural gas. The aim of this study was to investigate the responses of Tibouchina pulchra to the fuel switching. Saplings planted in pots were distributed throughout monitoring sites around the polluting source (sites I, II, III and IV) and in a site (V) far from emissions. Changes on the plants responses occur along the three fuel switching phases. During the last phase, increased carbon assimilation (Asat) and decreased stomatal conductance (gs) were observed in plants growing in sites II and III; as a consequence, intrinsic water use efficiency (iWUE) increased. However, the increase in Asat did not promote growth increase suggesting that changes at the refinery did not result in better air quality, but only in a change in the main contaminants. PMID:23352657

Silva, Daiane T; Moraes, Regina M

2013-04-01

35

Determination of five flavonoids in different parts of Fordia cauliflora by ultra performance liquid chromatography/triple-quadrupole mass spectrometry and chemical comparison with the root of Millettia pulchra var. laxior  

PubMed Central

Background The root of Fordia cauliflora Hemsl (FC) has long been used in southern China for the treatment of rheumatism, bruises, dementia in children, and valetudinarianism. However, sometimes it is mixed with other parts. And it has always been confused with the root of Millettia pulchra (Benth.) Kurz var. laxior (Dunn) Z. Wei (MP) by the local people. The chemical differences between the two ethnic drugs are not clear until now. The aim of this study is to develop a precise and accurate method to characterize and quantify multiple chemical components of FC, which is helpful for the quality evaluation and identification of FC. Results A method coupling ultra performance liquid chromatography (UPLC) with triple-quadrupole mass spectrometry (QqQ-MS) was first developed for simultaneous determination of five flavonoids in different parts of FC and the root of MP, based on a UPLC-diode array detection (DAD) fingerprint method. All calibration curves showed good linearity (R2>0.99) within test ranges. The overall LOD and LOQ were lower than 2.5 ng/mL and 5.0 ng/mL, respectively. The RSDs for intra- and inter-day of five analytes were less than 2.83% and 3.04%, respectively. Recovery studies for the quantified compounds were found to be within the range 93.6-99.8% with RSD less than 5.73%. The results suggest that the root, traditionally used medicinal part, yields the highest flavanoid content in FC. Pachycarin A, 3?,4?-dimethoxy(2??,3??:7,8) furanoflavone, karanjachromene and isoderricin A can be used to differentiate between FC and MP samples. Conclusions The present method is specific, precise and reliable, and is suitable for characterizing and quantifying multiple chemical components of FC. PMID:23870070

2013-01-01

36

Mating systems and interfertility of swamp milkweed (Asclepias incarnata ssp. incarnata and ssp. pulchra)  

Microsoft Academic Search

We investigated the breeding system and interfertility of both subspecies of Asclepias incarnata. We performed hand-pollinations in the glasshouse to compare fruit-set from self- vs. cross-pollinations and to assess interfertility in crosses between the subspecies. We also used horizontal starch-gel electrophoresis to infer mating-system parameters from open-pollinated progeny arrays in three natural populations over two consecutive years. Plants of ssp.

CHRISTOPHER T. IVEY; SARA R. LIPOW; Robert Wyatt

1999-01-01

37

The phylogenetic position of Acoela as revealed by the complete mitochondrial genome of Symsagittifera roscoffensis  

PubMed Central

Background Acoels are simply organized unsegmented worms, lacking hindgut and anus. Several publications over recent years challenge the long-held view that acoels are early offshoots of the flatworms. Instead a basal position as sister group to all other bilaterian animals was suggested, mainly based on molecular evidence. This led to the view that features of acoels might reflect those of the last common ancestor of Bilateria, and resulted in several evo-devo studies trying to interpret bilaterian evolution using acoels as a proxy model for the "Urbilateria". Results We describe the first complete mitochondrial genome sequence of a member of the Acoela, Symsagittifera roscoffensis. Gene content and circular organization of the mitochondrial genome does not significantly differ from other bilaterian animals. However, gene order shows no similarity to any other mitochondrial genome within the Metazoa. Phylogenetic analyses of concatenated alignments of amino acid sequences from protein coding genes support a position of Acoela and Nemertodermatida as the sister group to all other Bilateria. Our data provided no support for a sister group relationship between Xenoturbellida and Acoela or Acoelomorpha. The phylogenetic position of Xenoturbella bocki as sister group to or part of the deuterostomes was also unstable. Conclusions Our phylogenetic analysis supports the view that acoels and nemertodermatids are the earliest divergent extant lineage of Bilateria. As such they remain a valid source for seeking primitive characters present in the last common ancestor of Bilateria. Gene order of mitochondrial genomes seems to be very variable among Acoela and Nemertodermatida and the groundplan for the metazoan mitochondrial genome remains elusive. More data are needed to interpret mitochondrial genome evolution at the base of Bilateria. PMID:20942955

2010-01-01

38

Variation in resource availability changes the impact of invasive thistles on native bunchgrasses.  

PubMed

The threat posed by invasive nonnative plants to native plant populations is one of the largest challenges facing both conservation biology and restoration ecology. California has been highly impacted by invaders, although many relict stands of native plants are found on shallow, rocky soils with limited resources. The abiotic conditions of these sites may strongly influence the performance of an invasive plant and its effect on resident native species. In addition, the maturity of native plants in these sites may modulate an invader's impact; larger, well-established plants may be better able to resist invaders. In this study we examined how the impact of an invasive thistle (Centaurea solstitialis) on a native perennial bunchgrass (Nassella pulchra) changed in response to variation in soil depth, soil water availability, and bunchgrass maturity. We measured plant performance in terms of survival, growth, reproduction, and predawn water potential. We found that soil depth, water availability, and bunchgrass maturity acted in concert to influence the impact of the invasive thistle on the native bunchgrass. Both species performed better in deep soils, especially during dry years. The combination of shallow soil and low water availability reduced C. solstitialis performance and ameliorated its negative effect on N. pulchra growth and reproduction. Higher water availability resulted in a stronger negative effect of C. solstitialis on N. pulchra in both shallow and deep soils. However, as N. pulchra matured and increased in size, we saw a steady decline in C. solstitialis growth and reproductive output. Higher water availability increased the performance of C. solstitialis in shallow soils. C. solstitialis may thus have a stronger impact on N. pulchra and be more able to invade relict stands of N. pulchra in shallow soils during high-rainfall years. However, established stands of N. pulchra appear to be more resistant to invasion by C. solstitialis as N. pulchra plants grow older and larger. PMID:16711042

Morghan, Kimberly J Reever; Rice, Kevin J

2006-04-01

39

Ecology of benthic and epiphytic nematodes in brackish waters  

Microsoft Academic Search

Abundances of benthic nematodes from shallow waters in Tvärminne, Finland and in Ringkøbing Fjord, Denmark averaged 1.2–1.5\\u000a 106 individuals m?2. Less than 20 species were found. More than 80% of the individuals were made up by Anoplostoma viviparum, Chromadorita fennica, Axonolaimus spinosus, Daptonema trabeculosum and Sabatieria pulchra. S. pulchra is designated as an anoxybiotic species and is attracted to the

P. Jensen

1984-01-01

40

Inhibitory Effects of Secondary Metabolites from the Red Alga Delisea pulchraon Swarming Motility ofProteus mirabilis  

Microsoft Academic Search

Abnormal,uncoordinatedswarmingmotilityoftheopportunistichumanpathogenProteusmirabiliswasseen when a crude extract of the Australian red alga Delisea pulchra was added to the medium. This occurred at concentrations at which growth rate, swimming motility, cell elongation, polynucleation, and hyperflagellation were not affected. One halogenated furanone from D. pulchra inhibited swarming motility at concentrations that did not affect growth rate and swimming motility. Other structurally similarD. pulchrafuranones had

LONE GRAM; ROCKY DENYS; RIA MAXIMILIEN; MICHAEL GIVSKOV; PETER STEINBERG; ANDSTAFFAN KJELLEBERG

1996-01-01

41

Determination of total sulfur in lichens and plants by combustion-infrared analysis. [Medicago sativa L. ; Vitis labruscana Bailey; Festuca sp. ; Fraxinum pennsylvanica Marsh. ; Paremelia chlorochroa Tuck. ; P. sulcata Tayl. ; Juniperus scopulorum Sarg. ; Artemisia tridentata Nuttl; Lycopersicum esculentum Mill. ; Triticum compactum Host; Agropyron smithii Rydb. ; Salix pulchra Cham  

SciTech Connect

Sulfur was determined in plants and lichens by combustion of the sample and infrared detection of evolved sulfur dioxide using an automated sulfur analyzer. Vanadium pentaoxide was used as a combustion accelerator. Pelletization of the sample prior to combustion was not found to be advantageous. Washing studies showed that leaching of sulfur was not a major factor in the sample preparation. The combustion-IR analysis usually gave higher sulfur content than the turbidimetric analysis as well as shorter analysis time. Relative standard deviations of less than 7% were obtained by the combustion-IR technique when sulfur levels in plant material range from 0.05 to 0.70%. Determination of sulfur in National Bureau of Standards botanical reference materials showed good agreement between the combustion-IR technique and other instrumental procedures. Seven NBS botanical reference materials were analyzed.

Jackson, L.L.; Engleman, E.E.; Peard, J.L.

1985-01-01

42

Determination of total sulfur in lichens and plants by combustion-infrared analysis. [Medicago sativa L. ; Vitis labruscana Bailey; Festuca sp. ; Fraxinum pennsylvanica Marsh. ; Paremelia chlorochroa Tuck. ; P. sulcata Tayl. ; Juniperus scopulorum Sarg. ; Artemisia tridentata Nuttl; Lycopersicum esculentum Mill. ; Triticum compactum Host; Agropyron smithii Rydb. ; Salix pulchra Cham  

Microsoft Academic Search

Sulfur was determined in plants and lichens by combustion of the sample and infrared detection of evolved sulfur dioxide using an automated sulfur analyzer. Vanadium pentaoxide was used as a combustion accelerator. Pelletization of the sample prior to combustion was not found to be advantageous. Washing studies showed that leaching of sulfur was not a major factor in the sample

L. L. Jackson; E. E. Engleman; J. L. Peard

1985-01-01

43

The Acoela: on their kind and kinships, especially with nemertodermatids and xenoturbellids (Bilateria incertae sedis)  

PubMed Central

Acoels are among the simplest worms and therefore have often been pivotal in discussions of the origin of the Bilateria. Initially thought primitive because of their “planula-like” morphology, including their lumenless digestive system, they were subsequently dismissed by many morphologists as a specialized clade of the Platyhelminthes. However, since molecular phylogenies placed them outside the Platyhelminthes and outside all other phyla at the base of the Bilateria, they became the focus of renewed debate and research. We review what is currently known of acoels, including information regarding their morphology, development, systematics, and phylogenetic relationships, and put some of these topics in a historical perspective to show how the application of new methods contributed to the progress in understanding these animals. Taking all available data into consideration, clear-cut conclusions cannot be made; however, in our view it becomes successively clearer that acoelomorphs are a “basal” but “divergent” branch of the Bilateria. PMID:24098090

Chiodin, Marta; Salvenmoser, Willi; Tyler, Seth

2012-01-01

44

Combined large and small subunit ribosomal RNA phylogenies support a basal position of the acoelomorph flatworms.  

PubMed Central

The phylogenetic position of the phylum Platyhelminthes has been re-evaluated in the past decade by analysis of diverse molecular datasets. The consensus is that the Rhabditophora + Catenulida, which includes most of the flatworm taxa, are not primitively simple basal bilaterians but are related to coelomate phyla such as molluscs. The status of two other groups of acoelomate worms, Acoela and Nemertodermatida, is less clear. Although many characteristics unite these two groups, initial molecular phylogenetic studies placed the Nemertodermatida within the Rhabditophora, but placed the Acoela at the base of the Bilateria, distant from other flatworms. This contradiction resulted in scepticism about the basal position of acoels and led to calls for further data. We have sequenced large subunit ribosomal RNA genes from 13 rhabditophorans + catenulids, three acoels and one nemertodermatid, tripling the available data. Our analyses strongly support a basal position of both acoels and nemertodermatids. Alternative hypotheses are significantly less well supported by the data. We conclude that the Nemertodermatida and Acoela are basal bilaterians and, owing to their unique body plan and embryogenesis, should be recognized as a separate phylum, the Acoelomorpha. PMID:12803898

Telford, Maximilian J; Lockyer, Anne E; Cartwright-Finch, Chloë; Littlewood, D Timothy J

2003-01-01

45

SPATIAL DISTRIBUTION OF COFFEE AND SHADE TREES IDENTIFIED WITH ENDOPHYTIC BACTERIA USING DAS-ELISA FOR Xylella fastidiosa  

E-print Network

SPATIAL DISTRIBUTION OF COFFEE AND SHADE TREES IDENTIFIED WITH ENDOPHYTIC BACTERIA USING DAS) studied bacteria found in potential vectors such as Agallia pulchra, Apogonalia spp., Caribovia coffeacola Research Institute, Inc. Redlands, Cal. 92373), to visually assess trees associated with bacteria in four

Gilbes, Fernando

46

Expansion of Canopy-Forming Willows Over the Twentieth Century on Herschel Island, Yukon Territory, Canada  

E-print Network

of each of the dominant canopy-forming willow species (Salix richardsonii, Salix glauca and Salix pulchra, disease, or growing conditions. Keywords Arctic Á Tundra Á Climate change Á Willows (Salix spp.) Á Shrub and Zhang 2009). Willows (Salix spp.) are well adapted to invading ecosystems when conditions change. Pollen

Krebs, Charles J.

47

Radial Dispersion of Neighbors and the Small-Scale Competitive Impact of Two Annual Grasses on a  

E-print Network

. Amongst other invaders, two grasses Lolium multiflorum and Bromus hordeaceus, commonly dominate portions on these sites. Lolium multiflorum and B. hordeaceus were planted in 20 cm diameter circular plots at a constant. The presence of L. multiflorum was associated with a decrease in N. pulchra survival compared with plots

Rice, Kevin

48

Brominated Furanones Inhibit Biofilm Formation by Salmonella enterica Serovar Typhimurium  

Microsoft Academic Search

Salmonella enterica serovar Typhimurium is a main cause of bacterial food-borne diseases. As Salmonella can form biofilms in which it is better protected against antimicrobial agents on a wide diversity of surfaces, it is of interest to explore ways to inhibit biofilm formation. Brominated furanones, originally extracted from the marine alga Delisea pulchra, are known to interfere with biofilm formation

Joost C. A. Janssens; Hans Steenackers; Stijn Robijns; Edith Gellens; Jeremy Levin; Hui Zhao; Kim Hermans; David De Coster; Tine L. Verhoeven; Kathleen Marchal; Jos Vanderleyden; D. E. De Vos; S. C. J. De Keersmaecker

2008-01-01

49

SOIL FUNGI AND THE EFFECTS OF AN INVASIVE FORB ON GRASSES: NEIGHBOR IDENTITY MATTERS  

Microsoft Academic Search

We studied the effects of soil fungi on interactions between Centaurea mel- itensis, an exotic invasive weed in central California, and two co-occurring grasses, Nassella pulchra and Avena barbata. The fungicide benomyl reduced the abundance of arbuscular mycorrhizal (AM) fungi in plant roots but did not affect non-AM fungi. Centaurea plants grown alone were .50% smaller with the resident microbial

Ragan M. Callaway; Bruce E. Mahall; Chris Wicks; Joel Pankey; Catherine Zabinski

2003-01-01

50

Elongation factor 1-alpha sequences do not support an early divergence of the Acoela.  

PubMed

The phylogenetic position of the Acoela is a key problem in the understanding of metazoan evolution. Recent studies based on 18S ribosomal DNA (rDNA) sequences have placed the Acoela in an extremely basal position as the sister group to all other extant triploblastic animals, suggesting that the phylum Platyhelminthes is polyphyletic. In order to test the results obtained with 18S rDNA, we sequenced elongation factor 1-alpha (EF1a) for the acoel Convoluta roscoffensis and five species of Turbellaria (two polyclads, Leptoplana tremellaris, and Prostheceraeus vittatus, and three triclads, Crenobia alpina, Schmidtea polychroa, and Girardia tigrina). Phylogenetic analyses of EF1a sequences show that the acoel sequences branch within the Platyhelminthes, in opposition to the 18S rDNA data. Moreover, comparison of the central variable region of EF1a shows similar sequence signatures between C. roscoffensis and the three triclad species. Although EF1a sequences fail to prove the monophyly of the phylum Platyhelminthes, they do not confirm the early divergence of the Acoela. PMID:10889216

Berney, C; Pawlowski, J; Zaninetti, L

2000-07-01

51

Phylogenetic relationships among turbellarian orders inferred from 18S rDNA sequences.  

PubMed

The turbellarian flatworm is a key group to understand the origin and the early evolution of triploblastic, bilaterally symmetrical animals, but phylogenetic relationships among turbellarian orders have been a subject of debates for decades, especially on the position of the acoel turbellarians. Some workers have considered the acoel representing the most primitive turbellarian order but others have regarded them as regressive. We determined almost the entire lengths of the nucleotide sequences of 18S ribosomal RNA gene (rDNA) in 17 species from 9 turbellarian orders (the Acoela, Catenulida, Macrostomida, Lecithoepitheliata, Rhabdocoela, Prolecithophora, Proseriata, Tricladida, and Polycladida). After adding the sequences of a cestode, two trematodes and some diploblastic animals obtained from databases, we reconstructed phylogenetic trees using the neighbor-joining, maximum-likelihood and maximum-parsimony methods. All trees significantly indicated that the Acoela is the earliest divergent group among the turbellarian orders. The trees also suggested that the Tricladida evolved in the separate lineage from that of a cluster of the Catenulida, Macrostomida, Lecithoepitheliata, Rhabdocoela, Polycladida, Trematoda and Cestoda after the divergence of the Acoela. PMID:9004556

Katayama, T; Nishioka, M; Yamamoto, M

1996-10-01

52

Results of Surveys for Special Status Reptiles at the Site 300 Facilities of Lawrence Livermore National Laboratory  

SciTech Connect

The purpose of this report is to present the results of a live-trapping and visual surveys for special status reptiles at the Site 300 Facilities of Lawrence Livermore National Laboratory (LLNL). The survey was conducted under the authority of the Federal recovery permit of Swaim Biological Consulting (PRT-815537) and a Memorandum of Understanding issued from the California Department of Fish and Game. Site 300 is located between Livermore and Tracy just north of Tesla road (Alameda County) and Corral Hollow Road (San Joaquin County) and straddles the Alameda and San Joaquin County line (Figures 1 and 2). It encompasses portions of the USGS 7.5 minute Midway and Tracy quadrangles (Figure 2). Focused surveys were conducted for four special status reptiles including the Alameda whipsnake (Masticophis lateralis euryxanthus), the San Joaquin Whipsnake (Masticophis Hagellum ruddock), the silvery legless lizard (Anniella pulchra pulchra), and the California horned lizard (Phrynosoma coronanum frontale).

Woollett, J J

2008-09-18

53

Responses of a Remnant California Native Bunchgrass Population to Grazing, Burning and Climatic Variation  

Microsoft Academic Search

This study examined the interactive effects of grazing intensity and burning on a remnant population of the California native\\u000a bunchgrass Nassella pulchra. We measured growth, reproduction and mortality of permanently marked bunchgrasses and measured bunchgrass seedling recruitment\\u000a and density in permanent quadrats. We burned half of the treatment plots in late spring 1998. Grazing treatments were implemented\\u000a in 1998, 1999

Jaymee T. Marty; Sharon K. Collinge; Kevin J. Rice

2005-01-01

54

Differential gene expression shows natural brominated furanones interfere with the autoinducer-2 bacterial signaling system ofEscherichia coli  

Microsoft Academic Search

The quorum sensing disrupter (5Z)-4-bromo- 5-(bromomethylene)-3-butyl-2(5H)-furanone (furanone) of the alga Delisea pulchra was previously found by us (En- viron Microbiol 3:731-736, 2001) to inhibit quorum sensing in Escherichia coli via autoinducer-2 (AI-2, pro- duced by LuxS). In this study, DNA microarrays were used to study the genetic basis of this natural furanone inhibi- tion of AI-2 signaling (significant values with

Dacheng Ren; Laura A. Bedzyk; Rick W. Ye; Stuart M. Thomas; Thomas K. Wood

2004-01-01

55

Karyotype and DNA-content evolution in ten species of Crepis (Asteraceae) distributed in Bulgaria  

Microsoft Academic Search

Ten Crepis species from Bulgaria—five perennials (C. viscidula, C. paludosa, C. conyzaefolia, C. bithynica, C. schachtii), four annuals (C. pulchra, C. sancta, C. setosa, C. zacintha) and one biennial (C. biennis)—were analysed karyologically using haematoxylin staining, Feulgen cytophotometry (scanning densitometry and video-based image analysis), and DNA flow cytometry with propidium iodide. All taxa but the biennial are diploids with descending

DESSISLAVA DIMITROVA; JOHANN GREILHUBER

2000-01-01

56

Demographic consequences of disease in a habitat-forming seaweed and impacts on interactions between natural enemies.  

PubMed

Diseases affecting natural ecosystems are increasing in frequency and severity, but unless obviously catastrophic, the consequences of disease outbreaks are often overlooked, relative to other ecological processes (e.g., predation, competition). Disease can have profound effects on individuals and can also strongly influence interactions between infected hosts and their natural enemies. We investigated whether a novel bleaching disease affected the survival or performance of a habitat-forming red seaweed, Delisea pulchra. In addition, we investigated bidirectional, multipartite interactions between this seaweed host, its pathogens, and consumers. Although we found no negative impacts of disease on survival of D. pulchra, bleaching had substantial, negative consequences for affected individuals, including a dramatic drop in fecundity and a significant decrease in size. In the first direct demonstration of bacterial disease-mediated herbivory of seaweeds, herbivores generally preferred to consume bleached tissue in feeding trials, and we also found higher densities of herbivores on bleached than co-occurring, healthy algae at sites where herbivores were abundant. In a conceptually reciprocal test of the effects of herbivores on infection, we showed that simulated herbivory increased susceptibility to bleaching when algae were also exposed to cultures of a bacterial pathogen. Given the high proportions of D. pulchra affected by bleaching during peak periods, the impacts of this disease are likely to have important implications at the population level. This work highlights complex interactions between habitat-forming organisms and their natural enemies and further emphasizes the need to consider disease in ecological research. PMID:24649654

Campbell, Alexandra H; Vergés, Adriana; Steinberg, Peter D

2014-01-01

57

Myogenesis in the basal bilaterian Symsagittifera roscoffensis (Acoela)  

PubMed Central

Background In order to increase the weak database concerning the organogenesis of Acoela – a clade regarded by many as the earliest extant offshoot of Bilateria and thus of particular interest for studies concerning the evolution of animal bodyplans – we analyzed the development of the musculature of Symsagittifera roscoffensis using F-actin labelling, confocal laserscanning microscopy, and 3D reconstruction software. Results At 40% of development between egg deposition and hatching short subepidermal fibres form. Muscle fibre development in the anterior body half precedes myogenesis in the posterior half. At 42% of development a grid of outer circular and inner longitudinal muscles is present in the bodywall. New circular muscles either branch off from present fibres or form adjacent to existing ones. The number of circular muscles is higher than that of the longitudinal muscles throughout all life cycle stages. Diagonal, circular and longitudinal muscles are initially rare but their number increases with time. The ventral side bears U-shaped muscles around the mouth, which in addition is surrounded by a sphincter muscle. With the exception of the region of the statocyst, dorsoventral muscles are present along the entire body of juveniles and adults, while adults additionally exhibit radially oriented internal muscles in the anterior tip. Outer diagonal muscles are present at the dorsal anterior tip of the adult. In adult animals, the male gonopore with its associated sexual organs expresses distinct muscles. No specific statocyst muscles were found. The muscle mantles of the needle-shaped sagittocysts are situated along the lateral edges of the animal and in the posterior end close to the male gonopore. In both juveniles and adults, non-muscular filaments, which stain positively for F-actin, are associated with certain sensory cells outside the bodywall musculature. Conclusion Compared to the myoanatomy of other acoel taxa, Symsagittifera roscoffensis shows a very complex musculature. Although data on presumably basal acoel clades are still scarce, the information currently available suggests an elaborated musculature with longitudinal, circular and U-shaped muscles as being part of the ancestral acoel bodyplan, thus increasing the possibility that Urbilateria likewise had a relatively complicated muscular ground pattern. PMID:18803837

Semmler, Henrike; Bailly, Xavier; Wanninger, Andreas

2008-01-01

58

Contribution of relative growth rate to root foraging by annual and perennial grasses from California oak woodlands.  

PubMed

Plants forage for nutrients by increasing their root length density (RLD) in nutrient-rich soil microsites through root morphological changes resulting in increased root biomass density (RBD), specific root length (SRL), or branching frequency (BF). It is commonly accepted that fast-growing species will forage more than slow-growing species. However, foraging responses may be due solely to differences in relative growth rates (RGR). There is little evidence, after the effects of RGR are removed, that the fast versus slow foraging theory is correct. In a pot study, we evaluated foraging of four grass species that differed in RGR: one fast-growing annual species, Bromus diandrus, two intermediate-growing species, annual Bromus hordeaceus and perennial Elymus glaucus, and one slow-growing perennial species, Nassella pulchra. We harvested plants either at a common time (plants varied in size) or at a common leaf number (plants similar size, surrogate for common biomass). By evaluating species at a common time, RGR influenced foraging. Conversely, by evaluating species at a common leaf number, foraging could be evaluated independent of RGR. When RGR was allowed to contribute to foraging (common time harvest), foraging and RGR were positively correlated. B. diandrus (fast RGR) foraged to a greater extent than did E. glaucus (intermediate RGR) and N. pulchra (slow RGR). E. glaucus (intermediate RGR) foraged to a greater extent than N. pulchra (slow RGR). Root growth within nutrient-rich microsites was due to significant increases in RBD, not to modifications of SRL or BF. However, when RGR was not allowed to influence foraging (common leaf number harvest), none of the four species significantly enhanced RLD in nutrient-rich compared to control microsites. This suggests that RGR strongly influenced the ability of these grass species to forage and also supports the need to evaluate plastic root traits independent of RGR. PMID:12750991

Aanderud, Zachary T; Bledsoe, Caroline S; Richards, James H

2003-08-01

59

Differential ecophysiological response of deciduous shrubs and a graminoid to long-term experimental snow reductions and additions in moist acidic tundra, Northern Alaska.  

PubMed

Changes in winter precipitation that include both decreases and increases in winter snow are underway across the Arctic. In this study, we used a 14-year experiment that has increased and decreased winter snow in the moist acidic tussock tundra of northern Alaska to understand impacts of variation in winter snow depth on summer leaf-level ecophysiology of two deciduous shrubs and a graminoid species, including: instantaneous rates of leaf gas exchange, and ?(13)C, ?(15)N, and nitrogen (N) concentrations of Betula nana, Salix pulchra, and Eriophorum vaginatum. Leaf-level measurements were complemented by measurements of canopy leaf area index (LAI) and depth of thaw. Reductions in snow lowered summer leaf photosynthesis, conductance, and transpiration rates by up to 40% compared to ambient and deep snow conditions for Eriophorum vaginatum, and reduced Salix pulchra conductance and transpiration by up to 49%. In contrast, Betula nana exhibited no changes in leaf gas exchange in response to lower or deeper snow. Canopy LAI increased with added snow, while reduced winter snow resulted in lower growing season soil temperatures and reduced thaw depths. Our findings indicate that the spatial and temporal variability of future snow depth will have individualistic consequences for leaf-level C fixation and water flux by tundra species, and that these responses will be manifested over the longer term by changes in canopy traits, depth of thaw, soil C and N processes, and trace gas (CO2 and H2O) exchanges between the tundra and the atmosphere. PMID:24052332

Pattison, Robert R; Welker, Jeffrey M

2014-02-01

60

Plant neighborhood control of arbuscular mycorrhizal community composition.  

PubMed

Arbuscular mycorrhizal fungi (AMF) are important root symbionts that can provide benefits to plant hosts, yet we understand little about how neighboring hosts in a plant community contribute to the composition of the AMF community. We hypothesized that the composition of the plant neighborhood, including the identities of both host and neighbor, would alter AMF community composition. We tested this in a glasshouse experiment in which a native perennial grass (Nassella pulchra) and three annual grasses (Avena barbata, Bromus hordeaceaous and Vulpia microstachys) were grown in two neighborhoods: conspecific monocultures and heterospecific perennial-annual mixtures. To identify AMF taxa colonizing plant roots, we used a combination of terminal restriction fragment length polymorphism and cloning. Both host and neighbor were important in structuring AMF communities. Unique AMF communities were associated with each plant host in monoculture. In heterospecific neighborhoods, the annual neighbors V. microstachys, A. barbata, and B. hordeaceus influenced N. pulchra AMF in different ways (synergistic, controlling, or neutral) and the reciprocal effect was not always symmetric. Our findings support a community approach to AMF studies, which can be used to increase our understanding of processes such as invasion and succession. PMID:19496954

Hausmann, Natasha Teutsch; Hawkes, Christine V

2009-01-01

61

Phylogenetic position of the dicyemid mesozoa inferred from 18S rDNA sequences.  

PubMed

The dicyemid mesozoa, obligate symbionts in the cephalopod kidney, are simply organized multicellular animals. They have long been the subject of phylogenetic debates. Some authors have suggested that dicyemids represent an offshoot from an early metazoan ancestor. Other workers considered them to be degenerated progeny of higher metazoa, possibly parasitic trematodes. We determined the almost complete nucleotide sequences of 18S rDNA in two species of dicyemid, Dicyema orientale and Dicyema acuticephalum, isolated purely from cephalopod urine. We compared these sequences with sequences determined in the present study from three flatworm species, as well as with a variety of eukaryote sequences obtained from databases. The phylogenetic trees reconstructed with the use of the neighbor-joining, maximum-parsimony, and maximum-likelihood methods indicated that the dicyemids belong among the triploblastic animals (Bilateria). However, we cannot firmly establish the position of the dicyemids within the Bilateria because we cannot ignore the problem of long branch attraction between the myxozoans, dicyemids, nematodes, and acoel flatworms. The present results favor the hypothesis that the dicyemids do not represent an early divergent metazoan group, but rather a group degenerated from a triploblastic ancestor. PMID:8541419

Katayama, T; Wada, H; Furuya, H; Satoh, N; Yamamoto, M

1995-01-01

62

Nutrient fluxes in litterfall of a secondary successional alluvial rain forest in Southern Brazil.  

PubMed

During forest succession, litterfall nutrient fluxes increase significantly. The higher inputs of organic matter and nutrients through litterfall affects positively soil fertility and the species composition, which are essential components in forest restoration and management programs. In the present study, the input of nutrients to the forest soil via litterfall components was estimated for two sites of different development stages, in an early successional alluvial rain forest in Brazil. Litterfall returned to the soil, in kg/ha, ca. 93 N, 79 Ca, 24 K, 15 Mg, 6 P, 1.7 Mn, 0.94 Fe, 0.18 Zn, 0.09 Cu and 11.2 Al, in the site where trees were more abundant and had higher values of basal area. In the other area, where trees where less abundant and values of basal area were comparatively low, litterfall returned < 50% of those amounts to the forest soil, except for Al. The amount of Al that returned to the soil was similar in both areas due to the high contribution of Tibouchina pulchra (82% of Al returned). Comparatively, high proportion of three dominant native tree species (Myrsine coriacea, T. pulchra and Cecropia pachystachya) explained better litter nutrient use efficiency (mainly N and P) in the site with the least advanced successional stage. Although litterfall of these species show lower nutrient concentrations than the other tree species, their nutrient fluxes were high in both sites, indicating a certain independence from soil essential nutrients. Such feature of the native species is very advantageous and should be considered in forest restoration programs. PMID:22208099

Scheer, Maurício Bergamini; Gatti, Gustavo; Wisniewski, Celina

2011-12-01

63

Spatial polychaeta habitat potential mapping using probabilistic models  

NASA Astrophysics Data System (ADS)

The purpose of this study was to apply probabilistic models to the mapping of the potential polychaeta habitat area in the Hwangdo tidal flat, Korea. Remote sensing techniques were used to construct spatial datasets of ecological environments and field observations were carried out to determine the distribution of macrobenthos. Habitat potential mapping was achieved for two polychaeta species, Prionospio japonica and Prionospio pulchra, and eight control factors relating to the tidal macrobenthos distribution were selected. These included the intertidal digital elevation model (DEM), slope, aspect, tidal exposure duration, distance from tidal channels, tidal channel density, spectral reflectance of the near infrared (NIR) bands and surface sedimentary facies from satellite imagery. The spatial relationships between the polychaeta species and each control factor were calculated using a frequency ratio and weights-of-evidence combined with geographic information system (GIS) data. The species were randomly divided into a training set (70%) to analyze habitat potential using frequency ratio and weights-of-evidence, and a test set (30%) to verify the predicted habitat potential map. The relationships were overlaid to produce a habitat potential map with a polychaeta habitat potential (PHP) index value. These maps were verified by comparing them to surveyed habitat locations such as the verification data set. For the verification results, the frequency ratio model showed prediction accuracies of 77.71% and 74.87% for P. japonica and P. pulchra, respectively, while those for the weights-of-evidence model were 64.05% and 62.95%. Thus, the frequency ratio model provided a more accurate prediction than the weights-of-evidence model. Our data demonstrate that the frequency ratio and weights-of-evidence models based upon GIS analysis are effective for generating habitat potential maps of polychaeta species in a tidal flat. The results of this study can be applied towards conservation and management initiatives for the macrofauna of tidal flats.

Choi, Jong-Kuk; Oh, Hyun-Joo; Koo, Bon Joo; Ryu, Joo-Hyung; Lee, Saro

2011-06-01

64

Free-Nematodes in the NW Black Sea meiobenthos - diversity, abundance, distribution and importance as indicator of hypoxic waters  

NASA Astrophysics Data System (ADS)

The aim of this study performed within EU FP7 Hypox Project was to get deeper knowledge about species of nematodes that could be indicators for stressful biotic conditions as low oxygen concentration due to phenomena of seasonal hypoxia. The Nematodes come from meiobenthos sampling (using a multi corer with 4 tubes, Mark II type, lowered into the sea from R/V "Mare Nigrum" board) performed in May and September 2010 and April 2011 along four transects crossing the Romanian continental shelf from where 87 meiobenthos samples were collected. In the studied area 96 species of nematodes were found. The authors analyzed the nematodes populations' distribution on four profiles: Sf. Gheorghe, Portita, Constanta and Mangalia. The qualitative and quantitative structure of nematodes populations was compared. 41 species were found on Mangalia profile, 47 species on Portita profile, 48 species on Constanta profile and 85 species on Sf. Gheorghe profile. The greatest densities were found on Constanta profile with an average of 369.607indvs/m-2. The most frequent and abundant species were: Sabatieria pulchra, Sabatieria abyssalis, Terschellingia longicaudata, Viscosia cobbi, Axonolaimus ponticus. The species assemblages were assessed for depth gradient distribution, 7 depth intervals being set from 20 to 210 m. The greatest diversity was noted in 61-100 m depth interval, while the lowest between 0-20 m. On the contrary, in terms of density of individuals (indvs/m-2), highest densities were obtained in shallow waters between 21-30 m. As far as the depth increases, the species assemblages change, becoming more favorable to species like Halalaimus ponticus, Metachromadora macrouthera, Halanonchus bullatus, Linhomoneidae species. However, on the first place still remained Sabatieria abyssalis. The vertical distribution of nematodes in sediments was analyzed for the surface layer 0-5 cm and sub-surface layer 5-10 cm, the dominant species in both layers being: Sabatieria pulchra, S. abyssalis, Terschellingia longicaudata, Viscosia cobbi, Axonolaimus ponticus, Metalinhomoeus zosterae, Enoplus euxinus, Eleutherolaimus longus. The density decreases in 5-10 cm layer as compared to 0-5 cm layer. Results show that a dominant nematodes community tolerant to eutrophication conditions, organic loading and hypoxic conditions, made up of species of Sabatieria pulchra, Sabatieria abyssalis, Terschellingia longicaudata etc., is spread throughout the whole investigated area, from the shallow waters to the deepest bottoms at the limit of the metazoan life development. Literature confirms the ubiquitous distribution of these species, often found in areas of low O2 concentration. The taxonomic diversity increases with depth, which may suggest that the nematodes in the Black Sea, under unfavorable conditions, may have an adaptive strategy in response to the lack of resources or in the presence of physiological stress factors.

Muresan, M.; Gomoiu, M.-T.

2012-04-01

65

Characterizing Variation of Isotopic Markers in Northern Alaskan Caribou Forages  

NASA Astrophysics Data System (ADS)

Isotopic markers in feces and tissues are a potential tool for monitoring the importance of feeding areas for migratory herbivores such as caribou (Rangifer tarandus). Many of these techniques are currently limited by gaps in our knowledge of how these isotopic signatures vary over the landscape. We collected seven species of preferred caribou forages along a latitudinal gradient in the summer ranges of the Central Arctic (9 sites) and Teshekpuk Lake (4 sites) caribou herds during 2011 and 2012. We analyzed forages at peak protein content and at the end of the season to characterize temporal, species-specific, and spatial variation in isotopic markers. The availability of C and N was measured by digestion in vitro. Isotopic signatures of digested samples were used to calculate fractionation that would bias the isotopic signature of feces. The range of values for isotopes (all values ‰) of nitrogen (?15N -9.5 - +4.3), and sulfur (?34S -3.6 - +15.5) were greater than those for carbon (?13C -30.5 - -24.9). Small declines in forage ?13C with latitude (Carex aquatilis, Eriophorum vaginatum, Salix pulchra, and S. richardsonii [all P < 0.01]), season (all species except C. bigelowii [all P ? 0.01]), and season x year (S. richardsonii; P = 0.01) were probably associated with changes in water availability. Fractionation of ?13C in early season forages was 0.1 × 1.0 and positively related to C availability (58% × 15%; P < 0.01) with the greatest fractionation for the highly digestible forb Pedicularis langsdorfii (1.43 × 0.44; P < 0.01). Sedges (Carex and Eriophorum) were significantly higher in ?15N than Salix spp. and other dicots (2.0 × 1.1 vs. -2.9 × 2.2; P < 0.01). For Salix spp., ?15N was consistent over the season and between years. Fractionation of ?15N in early season forages was 0.2 × 1.8 and not related to N availability (60% × 17%). For S. pulchra, ?34S may indicate usage of coastal habitats over foothills because ?34S was higher on the coastal plain than in the foothills (11.1 × 3.3 and 3.1 × 2.6; P < 0.01). Isotopic ratios in N and S show the greatest promise for tracking diet and location of migratory caribou whereas the narrow range in ?13C is affected by species, season and location.

VanSomeren, L.; Barboza, P. S.; Gustine, D. D.; Parrett, L. S.; Stricker, C. A.

2013-12-01

66

Quantifying the physiology of structurally complex arctic vegetation and implications for carbon cycling in a shrubbier tundra  

NASA Astrophysics Data System (ADS)

The arctic is undergoing a warming trend that is more extreme compared to lower latitudes. As one major consequence, repeat aerial photographs reveal that in recent decades woody deciduous shrubs have increased in dominance in valley bottoms and riparian areas of northern Alaska. Advancing shrub canopies are growing taller and more structurally complex, presumably increasing self-shading and reducing light availability with canopy depth. According to canopy optimization theory, plants will preferentially allocate nutrient resources to sun-exposed canopy leaves to enhance photosynthetic efficiency in order to take advantage of greater light availability. While canopy optimization has been studied in other, mainly forested ecosystems, this theory has yet to be tested in the arctic tundra. We made a series of measurements on canopy leaves located in high to low light environments, from three common woody deciduous shrubs on the North Slope of Alaska: dwarf birch (Betula nana), tealeaf willow (Salix pulchra), and feltleaf willow (Salix alaxensis). For each selected leaf, we measured the canopy leaf area index at its canopy position in order to quantify the amount of light intercepted by the leaf surface, and in situ chlorophyll fluorescence to evaluate its photosynthetic efficiency through calculation of leaf maximum electron transport rate. The same leaves were then removed and measured for leaf area, dry mass, and carbon to nitrogen ratio. Our data show trends that are consistent with the development of canopy optimization. Leaf nitrogen decreases significantly from the upper to lower terciles of leaf area index values (56% in Salix alaxensis, 41% in Salix pulchra, 46% in Betula nana). Similarly, there were significant reductions in the leaf maximum electron transport rate for two species (44% in Salix alaxensis, 40% Betula nana). These findings suggest that structurally complex arctic shrubs may be redistributing leaf nitrogen to more exposed parts of the canopy where light is more abundant, which combined with higher photosynthetic efficiencies suggests that plants may be investing more nitrogen into photosynthetic machinery. Future work should focus on the relationship between chlorophyll fluorescence and leaf-level CO2 exchange in order to determine the relationship between the observed gradients in photosynthetic efficiency and measured carbon exchange. This study suggests that because the arctic tundra is becoming more structurally complex, ecosystem-level carbon models should include within-canopy gradients in light intensity and consequent gradients in leaf physiological traits.

Formica, A. F.; Griffin, K. L.; Boelman, N.

2013-12-01

67

Revision of the genus Turris Batsch, 1789 (Gastropoda: Conoidea: Turridae) with the description of six new species  

PubMed Central

The taxonomy of the genus Turris Batsch, 1789, type genus of the family Turridae, widespread in shallow-water habitats of tropic Indo-Pacific, is revised. A total of 31 species of Turris, are here recognized as valid. New species described: Turris chaldaea, Turris clausifossata, Turris guidopoppei, Turris intercancellata, Turris kantori, T. kathiewayae. Homonym renamed: Turris bipartita nom. nov. for Pleurotoma variegata Kiener, 1839 (non Philippi, 1836). New synonymies: Turris ankaramanyensis Bozzetti, 2006 = Turris tanyspira Kilburn, 1975; Turris imperfecti, T. nobilis, T. pulchra and T. tornatum Röding, 1798, and Turris assyria Olivera, Seronay & Fedosov, 2010 = T. babylonia; Turris dollyi Olivera, 2000 = Pleurotoma crispa Lamarck, 1816; Turris totiphyllis Olivera, 2000 = Turris hidalgoi Vera-Peláez, Vega-Luz & Lozano-Francisco, 2000; Turris kilburni Vera-Peláez, Vega-Luz & Lozano-Francisco, 2000 = Turris pagasa Olivera, 2000; Turris (Annulaturris) munizi Vera-Peláez, Vega-Luz & Lozano-Francisco, 2000 = Gemmula lululimi Olivera, 2000. Revised status: Turris intricata Powell, 1964, Pleurotoma variegata Kiener, 1839 (non Philippi, 1836) and Pleurotoma yeddoensis Jousseaume, 1883, are regarded as full species (not subspecies of Turris crispa). Neotype designated: For Pleurotoma garnonsii Reeve, 1843, to distinguish it from Turris garnonsii of recent authors, type locality emended to Zanzibar. New combination: Turris orthopleura Kilburn, 1983, is transferred to genus Makiyamaia, family Clavatulidae. PMID:23847408

Kilburn, Richard N.; Fedosov, Alexander E.; Olivera, Baldomero M.

2012-01-01

68

Invasive annual grasses indirectly increase virus incidence in California native perennial bunchgrasses.  

PubMed

In California valley grasslands, Avena fatua L. and other exotic annual grasses have largely displaced native perennial bunchgrasses such as Elymus glaucus Buckley and Nassella pulchra (A. Hitchc.) Barkworth. The invasion success and continued dominance of the exotics has been generally attributed to changes in disturbance regimes and the outcome of direct competition between species. Here, we report that exotic grasses can also indirectly increase disease incidence in nearby native grasses. We found that the presence of A. fatua more than doubled incidence of infection by barley and cereal yellow dwarf viruses (B/CYDVs) in E. glaucus. Because B/CYDV infection can stunt E. glaucus and other native bunchgrasses, the indirect effects of A. fatua on virus incidence in natives suggests that apparent competition may be an additional mechanism influencing interactions among exotic and native grasses in California. A. fatua's influence on virus incidence is likely mediated by its effects on populations of aphids that vector B/CYDVs. In our study, aphids consistently preferred exotic annuals as hosts and experienced higher fecundity on them, suggesting that the exotics can attract and amplify vector populations. To the best of our knowledge, these findings are the first demonstration that exotic plants can indirectly influence virus incidence in natives. We suggest that invasion success may be influenced by the capacity of exotic plant species to increase the pathogen loads of native species with which they compete. PMID:15875144

Malmstrom, Carolyn M; McCullough, April J; Johnson, Hope A; Newton, Linsey A; Borer, Elizabeth T

2005-08-01

69

Revision, cladistic analysis and biogeography of Typhochlaena C. L. Koch, 1850, Pachistopelma Pocock, 1901 and Iridopelma Pocock, 1901 (Araneae, Theraphosidae, Aviculariinae)  

PubMed Central

Abstract Three aviculariine genera endemic to Brazil are revised. Typhochlaena C. L. Koch, 1850 is resurrected, including five species; Pachistopelma Pocock, 1901 includes two species; and Iridopelma Pocock, 1901, six species. Nine species are newly described: Typhochlaena amma sp. n., Typhochlaena costae sp. n., Typhochlaena curumim sp. n., Typhochlaena paschoali sp. n., Pachistopelma bromelicola sp. n., Iridopelma katiae sp. n., Iridopelma marcoi sp. n., Iridopelma oliveirai sp. n. and Iridopelma vanini sp. n. Three new synonymies are established: Avicularia pulchra Mello-Leitão, 1933 and Avicularia recifiensis Struchen & Brändle, 1996 are junior synonyms of Pachistopelma rufonigrum Pocock, 1901 syn. n., and Avicularia palmicola Mello-Leitão, 1945 is a junior synonym of Iridopelma hirsutum Pocock, 1901 syn. n. Pachistopelma concolor Caporiacco, 1947 is transferred to Tapinauchenius Ausserer, 1871, making the new combination Tapinauchenius concolor (Caporiacco, 1947) comb. n. Lectotypes are newly designed for Pachistopelma rufonigrum Pocock, 1901 , Iridopelma hirsutum Pocock, 1901 and Pachistopelma concolor Caporiacco, 1947. Cladistic analyses using both equal and implied weights were carried out with a matrix comprising 62 characters and 38 terminal taxa. The chosen cladogram found with X-Pee-Wee and concavity 6 suggests they are monophyletic. All species are keyed and mapped and information on species habitat and area cladograms are presented. Discussion on biogeography and conservation is provided. PMID:23166476

Bertani, Rogerio

2012-01-01

70

Expansion of canopy-forming willows over the twentieth century on Herschel Island, Yukon Territory, Canada.  

PubMed

Canopy-forming shrubs are reported to be increasing at sites around the circumpolar Arctic. Our results indicate expansion in canopy cover and height of willows on Herschel Island located at 70 degrees north on the western Arctic coast of the Yukon Territory. We examined historic photographs, repeated vegetation surveys, and conducted monitoring of long-term plots and found evidence of increases of each of the dominant canopy-forming willow species (Salix richardsonii, Salix glauca and Salix pulchra), during the twentieth century. A simple model of patch initiation indicates that the majority of willow patches for each of these species became established between 1910 and 1960, with stem ages and maximum growth rates indicating that some patches could have established as late as the 1980s. Collectively, these results suggest that willow species are increasing in canopy cover and height on Herschel Island. We did not find evidence that expansion of willow patches is currently limited by herbivory, disease, or growing conditions. PMID:21954724

Myers-Smith, Isla H; Hik, David S; Kennedy, Catherine; Cooley, Dorothy; Johnstone, Jill F; Kenney, Alice J; Krebs, Charles J

2011-09-01

71

?-Alkylidene-?-lactones and isobutylpyrrol-2(5H)-ones analogues to rubrolides as inhibitors of biofilm formation by gram-positive and gram-negative bacteria.  

PubMed

Several molecules have been discovered that interfere with formation of bacterial biofilms, opening a new strategy for the development of more efficient treatments in case of antibiotic resistant bacteria. Amongst the most active compounds are some natural brominated furanones from marine algae Delisea pulchra that have proven to be able to control pathogenic biofilms. We have recently reported that some rubrolide analogues are able to inhibit biofilm formation of Enterococcus faecalis. In the present Letter we describe results of the biological evaluation of a small library of 28 compounds including brominated furanones and the corresponding lactams against biofilm formation of Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus epidermidis and Streptococcus mutans. Our results showed that in general these compounds were more active against biofilms of S. epidermidis and P. aeruginosa, with little or no inhibition of planktonic bacterial growth. In some cases they were able to prevent biofilm formation of P. aeruginosa at concentrations as low as 0.6 ?g/mL (1.3 ?M, compound 3d) and 0.7 ?g/mL (1.3 ?M, 3f). Results also indicate that, in general, lactams are more active against biofilms than their precursors, thus designating this class of molecules as good candidates for the development of a new generation of antimicrobial drugs targeted to biofilm inhibition. PMID:24484899

Pereira, Ulisses A; Barbosa, Luiz C A; Maltha, Célia R A; Demuner, Antônio J; Masood, Mohammed A; Pimenta, Andréa L

2014-02-15

72

SPECIES COMPOSITION OF CARRION BLOW FLIES IN NORTHERN THAILAND: ALTITUDE APPRAISAL  

PubMed Central

Distribution and occurrence of blow flies of forensic importance was performed during 2007 and 2008 in Chiang Mai and Lampang Provinces, northern Thailand. Surveys were conducted in forested areas for 30 minutes using a sweep net to collected flies attracted to a bait. A total of 2,115 blow flies belonging to six genera and 14 species were collected; Chrysomya megacephala (Fabricius) (44.7%), C. pinguis (Walker) (15.1%), C. chani Kurahashi (9.3%), C. thanomthini Kurahashi & Tumrasvin (0.3%); Achoetandrus rufifacies (Macquart) (10.5%), A. villeneuvi (Patton) (2.2%); Lucilia papuensis Macquart (2.2%), L. porphyrina (Walker) (12.4%), L. sinensis Aubertin (0.7%); Hemipyrellia ligurriens (Wiedemann) (1.3%), H. pulchra (Wiedemann) (0.1%); Hypopygiopsis infumata (Bigot) (0.6%), Hy. tumrasvini Kurahashi (0.2%) and Ceylonomyia nigripes Aubertin (0.4%). Among them, C. megacephala was the predominant species collected, particularly in the summer. The species likely to prevail in highland areas are C. pinguis, C. thanomthini, Hy. tumrasvini, L. papuensis and L. porphyrina. PMID:24626423

Moophayak, Kittikhun; Klong-Klaew, Tunwadee; Sukontason, Kom; Kurahashi, Hiromu; Tomberlin, Jeffery K.; Sukontason, Kabkaew L.

2014-01-01

73

Leaves of Lolium multiflorum 'Lema' and tropical tree species as biomonitors of polycyclic aromatic hydrocarbons.  

PubMed

This study extends the current knowledge regarding the use of plants for the passive accumulation of anthropogenic PAHs that are present in the atmospheric total suspended particles (TSP) in the tropics and sub-tropics. It is of major relevance because the anthropic emissions of TSP containing PAHs are significant in these regions, but their monitoring is still scarce. We compared the biomonitor efficiency of Lolium multiflorum 'Lema' and tropical tree species (Tibouchina pulchra and Psidium guajava 'Paluma') that were growing in an intensely TSP-polluted site in Cubatão (SE Brazil), and established the species with the highest potential for alternative monitoring of PAHs. PAHs present in the TSP indicated that the region is impacted by various emission sources. L. multiflorum showed a greater efficiency for the accumulation of PAH compounds on their leaves than the tropical trees. The linear regression between the logBCF and logKoa revealed that L. multiflorum is an efficient biomonitor of the profile of light and heavy PAHs present in the particulate phase of the atmosphere during dry weather and mild temperatures. The grass should be used only for indicating the PAHs with higher molecular weight in warmer and wetter periods. PMID:22285658

Rinaldi, Mirian C S; Domingos, Marisa; Dias, Ana P L; Esposito, Jéssica B N; Pagliuso, Josmar D

2012-05-01

74

Biogeochemical characterization of an undisturbed highly acidic, metal-rich bryophyte habitat, east-central Alaska, U.S.A.  

USGS Publications Warehouse

We report on the geochemistry of soil and bryophyte-laden sediment and on the biogeochemistry of willows growing in an undisturbed volcanogenic massive sulfide deposit in the Alaska Range ecoregion of east-central Alaska. We also describe an unusual bryophyte assemblage found growing in the acidic metal-rich waters that drain the area. Ferricrete-cemented silty alluvial sediments within seeps and streams are covered with the liverwort Gymnocolea inflata whereas the mosses Polytrichum commune and P. juniperinum inhabit the area adjacent to the water and within the splash zone. Both the liverwort-encrusted sediment and Polytrichum thalli have high concentrations of major and trace metal cations (e.g., Al, As, Cu, Fe, Hg, La, Mn, Pb, and Zn). Soils in the area do not reflect the geochemical signature of the mineral deposit and we postulate they are influenced by the chemistry of eolian sediments derived from outside the deposit area. The willow, Salix pulchra, growing mostly within and adjacent to the larger streams, has much higher concentrations of Al, As, Cd, Cr, Fe, La, Pb, and Zn when compared to the same species collected in non-mineralized areas of Alaska. The Cd levels are especially high and are shown to exceed, by an order of magnitude, levels demonstrated to be toxic to ptarmigan in Colorado. Willow, growing in this naturally occurring metal-rich Red Mountain alteration zone, may adversely affect the health of browsing animals. ?? 2006 Regents of the University of Colorado.

Gough, L.P.; Eppinger, R.G.; Briggs, P.H.; Giles, S.

2006-01-01

75

Distribution and biomass of arrow worms (Chaetognatha) in Golfo de Nicoya and Golfo Dulce, Costa Rica.  

PubMed

The chaetognath species guild was analyzed from samples collected during the cruise of the German RV Victor Hensen to the Pacific coast of Costa Rica in December 1993 and February, 1994, finding the following ten species of the genera Sagitta and Krohnitta: S. enflata, S. hexaptera, S. pacifica, S. neglecta, S. regularis, S. bedoti, S. friderici, S. popovicii, S. pulchra and K. pacifica. Because of their distributional patterns in the study area these species were ascribed to the following ecological groups: neritic, semi-neritic and oceanic. A strong gradient in species richness from offshore to inshore waters (8 to one respectively) was found in both gulf systems. Inshore chaetognaths were dominated by juveniles and adults of S. friderici in Golfo de Nicoya and by S. popovicii in Golfo Dulce. Biomass spectra were more continuous and of wider range in the Golfo Dulce area showing a dominance of larger chaetognaths, suggesting a more general developed pelagic system in Golfo Dulce, where larger chaetognaths might structure the plankton community by strong grazing pressure from above. PMID:9393651

Hossfeld, B

1996-12-01

76

The Cell's View of Animal Body-Plan Evolution.  

PubMed

An adult animal's form is shaped by the collective behavior of cells during embryonic development. To understand the forces that drove the divergence of animal body-plans, evolutionary developmental biology has focused largely on studying genetic networks operating during development. However, it is less well understood how these networks modulate characteristics at the cellular level, such as the shape, polarity, or migration of cells. We organized the "Cell's view of animal body plan evolution" symposium for the 2014 The Society for Integrative and Comparative Biology meeting with the explicit goal of bringing together researchers studying the cell biology of embryonic development in diverse animal taxa. Using a broad range of established and emerging technologies, including live imaging, single-cell analysis, and mathematical modeling, symposium participants revealed mechanisms underlying cells' behavior, a few of which we highlight here. Shape, adhesion, and movements of cells can be modulated over the course of evolution to alter adult body-plans and a major theme explored during the symposium was the role of actomyosin in coordinating diverse behaviors of cells underlying morphogenesis in a myriad of contexts. Uncovering whether conserved or divergent genetic mechanisms guide the contractility of actomyosin in these systems will be crucial to understanding the evolution of the body-plans of animals from a cellular perspective. Many speakers presented research describing developmental phenomena in which cell division and tissue growth can control the form of the adult, and other presenters shared work on studying cell-fate specification, an important source of novelty in animal body-plans. Participants also presented studies of regeneration in annelids, flatworms, acoels, and cnidarians, and provided a unifying view of the regulation of cellular behavior during different life-history stages. Additionally, several presentations highlighted technological advances that glean mechanistic insights from new and emerging model systems, thereby providing the phylogenetic breadth so essential for studying animal evolution. Thus, we propose that an explicit study of cellular phenomena is now possible for a wide range of taxa, and that it will be highly informative for understanding the evolution of animal body-plans. PMID:25108284

Lyons, Deirdre C; Martindale, Mark Q; Srivastava, Mansi

2014-10-01

77

Examining vertical patterns in Arctic tundra shrub canopies: Implications for carbon cycling in a changing environment  

NASA Astrophysics Data System (ADS)

Climate change is facilitating the northward encroachment and expansion of woody shrub species into the Arctic tundra, which in turn is altering a number of physical and biogeochemical processes that are likely to affect how carbon is cycled in this region. Greater shrub presence also increases leaf area index and canopy complexity in the tundra, introducing the potential for vertical variation in nitrogen, photosynthesis, and respiration through the canopy. For these reasons, Arctic tundra shrub communities represent an ecologically relevant case study for investigating carbon cycling-nitrogen relationships and testing optimization models. Here, we measured photosynthesis, respiration in the dark and light, the light inhibition of respiration, stomatal conductance, leaf nitrogen, and related leaf traits at different heights representing variation in light availability in multiple Arctic Alaskan shrub communities dominated by Salix pulchra and Betula nana to examine if the relatively low-stature canopies exhibit vertical patterns. Highest rates of photosynthesis and respiration (P < 0.0001) were observed at the top of the canopy, suggesting substrate-limitation of respiration at lower, more shaded canopy levels. Leaves at the top of the canopy also exhibited the lowest inhibition of respiration by light (NS), and the highest nitrogen concentrations. (P < 0.05) implying a relationship between photosynthesis, nitrogen, and a relaxation of light-inhibition to optimize metabolic efficiency. Data from this study was also used to test leaf-level and canopy nitrogen optimization models. These data emphasize the need to include canopy complexity in tundra carbon models, as neglecting physiological differences through a canopy may lead to an underestimation of stored carbon.

Heskel, M.; Atkin, O.; Turnbull, M.; Rastetter, E.; Griffin, K. L.

2012-12-01

78

The Genera of Fungi: fixing the application of type species of generic names.  

PubMed

To ensure a stable platform for fungal taxonomy, it is of paramount importance that the genetic application of generic names be based on their DNA sequence data, and wherever possible, not morphology or ecology alone. To facilitate this process, a new database, accessible at www.GeneraofFungi.org (GoF) was established, which will allow deposition of metadata linked to holo-, lecto-, neo- or epitype specimens, cultures and DNA sequence data of the type species of genera. Although there are presently more than 18 000 fungal genera described, we aim to initially focus on the subset of names that have been placed on the "Without-prejudice List of Protected Generic Names of Fungi" (see IMA Fungus 4(2): 381-443, 2013). To enable the global mycological community to keep track of typification events and avoid duplication, special MycoBank Typification identfiers (MBT) will be issued upon deposit of metadata in MycoBank. MycoBank is linked to GoF, thus deposited metadata of generic type species will be displayed in GoF (and vice versa), but will also be linked to Index Fungorum (IF) and the curated RefSeq Targeted Loci (RTL) database in GenBank at the National Center for Biotechnology Information (NCBI). This initial paper focuses on eight genera of appendaged coelomycetes, the type species of which are neo- or epitypified here: Bartalinia (Bartalinia robillardoides; Amphisphaeriaceae, Xylariales), Chaetospermum (Chaetospermum chaetosporum, incertae sedis, Sebacinales), Coniella (Coniella fragariae, Schizoparmaceae, Diaporthales), Crinitospora (Crinitospora pulchra, Melanconidaceae, Diaporthales), Eleutheromyces (Eleutheromyces subulatus, Helotiales), Kellermania (Kellermania yuccigena, Planistromataceae, Botryosphaeriales), Mastigosporium (Mastigosporium album, Helotiales), and Mycotribulus (Mycotribulus mirabilis, Agaricales). Authors interested in contributing accounts of individual genera to larger multi-authored papers to be published in IMA Fungus, should contact the associate editors listed below for the major groups of fungi on the List of Protected Generic Names for Fungi. PMID:25083414

Crous, Pedro W; Giraldo, Alejandra; Hawksworth, David L; Robert, Vincent; Kirk, Paul M; Guarro, Josep; Robbertse, Barbara; Schoch, Conrad L; Damm, Ulrike; Trakunyingcharoen, Thippawan; Groenewald, Johannes Z

2014-06-01

79

Long-term deeper snow causes changes in litter quality, soil C and N storage in moist acidic tundra in Northern Alaska  

NASA Astrophysics Data System (ADS)

Tundra ecosystems store over one third of the global terrestrial organic C pool and have the potential to release large amounts of CO2 as organic matter decomposition is expected to increase as climate warms and precipitation changes. However, a warming climate and increased snow pack soil thermal insulation is expected to shift dominant vegetative cover type affecting above and below ground litter quality, soil organic matter storage depth, and decomposition rates in respective soils. These changes can affect the magnitude and even direction of soil C storage in the Arctic tundra.. At a sixteen-year snow fence experiment at Toolik Lake, as part of the International Tundra Experiment (ITEX), increased snow pack resulted in a shift from a Sphagnum moss-dominated mixed graminoid-deciduous ecosystem (moist tussock tundra) to one covered largely by deciduous shrubs and Carex in more water-saturated soil conditions. We investigated relationships between shifting dominance of plant species and impacts to soils using a multiproxy isotope and biomarker approach in plants and soils from the areas with control, deep, intermediate, and low snow pack. A comparison of the same plant species (Betula nana, Carex bigelowii, Eriophorum vaginatum, Salix pulchra, and Sphagnum spp.) along the snow zones showed leaf tissue C-to-N ratio decreasing in the deep snow areas when compared to control and low snow pack areas, driven by an increase in plant N content. Root and stem tissue was impacted similarly across the experimental treatments. Changes in soil ?13C and ?15N values with depth and along the transect demonstrate impacts to C and N cycling. These results demonstrate litter quality and soil carbon storage feedbacks in response to snow pack thermal insulation that could influence litter accumulation, decay rates and the chemical nature of soil carbon under climate conditions with deeper snow in winter.

Miller, O.; Xu, D.; Gonzalez-Meler, M. A.; Welker, J. M.; Filley, T. R.

2013-12-01

80

Willow Shrub Expansion Following Tundra Fires in Arctic Alaska  

NASA Astrophysics Data System (ADS)

Climate warming in the Arctic is predicted to result in the expansion of woody shrubs and increased frequency and size of tundra fires. How will fire influence this shrub expansion? Over a period of 32 years, following a 1977 tundra fire in the central Seward Peninsula, we sampled seven times the post-fire vegetation at eight permanently marked sites on a long (2 Km) hillslope (Nimrod Hill). We had previously sampled vegetation here in 1973 prior to the fire. By 2001, 24 years post-fire conspicuous willow shrubs (mostly Salix pulchra) had increased in numbers, size and cover over the entire slope in moist tussock-shrub tundra, well-drained heath, and wet meadow. Prior to fire, willow on this slope was largely restricted to small drainages or watertracks. Willows here have originated from both seed and vegetative resprouting - the latter mostly in moist tussock-shrub tundra from willows resprouting within one to three years post-fire. With fire-induced removal of vascular plant competition and Spagnum moss cover and litter in tussock-shrub tundra, both seedling and resprouting willows have grown rapidly to overtop tussocks by 30-40 cm. Similar rapid post-fire resprouting of willows has been observed in tussock-shrub tundra after the 2007 Anaktuvuk River tundra fire and after the 1977 tundra fires in the Noatak River basin. On Nimrod Hill the most striking willow expansion has occurred on the severely burned and well-drained backslope where willow establishment from seed 5-10 years after fire has resulted in up to 40% cover of rapidly growing willows of both upright and spreading growth form. At several sites along the slope there is evidence of continuing willow expansion from seedlings 24 to 32 years post-fire, when we might expect the effects of fire on seedbeds would have ceased. We conclude that tundra fire may promote shrub expansion in the Arctic.

Racine, C.

2010-12-01

81

Increasing NDVI values in northern Alaska: studies that mix shrub density, spectral and CO2 exchange measurements  

NASA Astrophysics Data System (ADS)

Delineating the mechanisms and consequences of changes in tundra landscapes is central to predicting the functional ecology of Alaska in the 21st Century. Evidence has been mounting during the last decade that shrub communities are expanding in the Arctic and Normalized Difference Vegetation Index (NDVI) values which measure surface greenness are rising. Several studies have suggested that NDVI increases are being driven by increases in shrub abundance. While it is clear that NDVI has increased across vegetation types, it is not clear that NDVI values are increasing in moist acidic tundra (MAT), the most extensive vegetation type in arctic Alaska and the one most likely to be changed by global warming. The MAT is important to large mammal herbivores such as caribou which provide subsistence for indigenous people. The focus of this research was to determine what rising NDVI values actually mean in the MAT. The degree to which tundra community composition affects NDVI is still very poorly understood. In order to clarify the role of shrub encroachment per se as opposed to other functional groups in driving increases in NDVI, we measured functional group composition in moist acidic tundra in conjunction with hand-held measures of NDVI and direct CO2 exchange measurements to explicitly link spectral properties, shrub, graminoid and bryophyte density and trace gas feedbacks to atmospheric chemistry. Point frame data shows a shrub coverage of Betula nana (Dwarf Birch) and Salix pulchra (Diamond Leaf Willow) combined of 5% to 35% in MAT. Our results seem to indicate that high shrub density (>30%) corresponds to peak season NDVI values greater than .75 whereas low shrub density correspond to values below .65 (R2=.66). Furthermore, NDVI is closely correlated with canopy leaf area and greater leaf area is associated with higher rates of gross and net ecosystem CO2 uptake.

Anderson-Smith, A.; Lewis, A.; Sullivan, P.; Welker, J. M.

2010-12-01

82

Sensitive Species of Snakes, Frogs, and Salamanders in Southern California Conifer Forest Areas: Status and Management 1  

E-print Network

At least 35 species of amphibians and reptiles occur regularly in the conifer forest areas of southern California. Twelve of them have some or all of their populations identified as experiencing some degree of threat. Among the snakes, frogs, and salamanders that we believe need particular attention are the southern rubber boa (Charina bottae umbratica), San Bernardino mountain kingsnake (Lampropeltis zonata parvirubra), San Diego mountain kingsnake (L.z. pulchra), California red-legged frog (Rana aurora draytonii), mountain yellow-legged frog (R. muscosa), San Gabriel Mountain slender salamander (Batrachoseps gabrieli), yellow-blotched salamander (Ensatina eschscholtzii croceater), and large-blotched salamander (E.e. klauberi). To varying degrees, these taxa face threats of habitat degradation and fragmentation, as well as a multitude of other impacts ranging from predation by alien species and human collectors to reduced genetic diversity and chance environmental catastrophes. Except for the recently described San Gabriel Mountain slender salamander, all of these focus taxa are included on Federal and/or State lists of endangered, threatened, or special concern species. Those not federally listed as Endangered or Threatened are listed as Forest Service Region 5 Sensitive Species. All of these taxa also are the subjects of recent and ongoing phylogeographic studies, and they are of continuing interest to biologists studying the evolutionary processes that shape modern species of terrestrial vertebrates. Current information on their taxonomy, distribution, habits and problems is briefly reviewed and management recommendations are made. Further research is needed to elucidate their biological status and needs and to provide the basis for appropriate management programs. Programs must be monitored to ensure that desired objectives are achieved.

Glenn R. Stewart; Mark R. Jennings; Robert H. Goodman

83

Arbuscular mycorrhizal assemblages in native plant roots change in the presence of invasive exotic grasses  

USGS Publications Warehouse

Plant invasions have the potential to significantly alter soil microbial communities, given their often considerable aboveground effects. We examined how plant invasions altered the arbuscular mycorrhizal fungi of native plant roots in a grassland site in California and one in Utah. In the California site, we used experimentally created plant communities composed of exotic (Avena barbata, Bromus hordeaceus) and native (Nassella pulchra, Lupinus bicolor) monocultures and mixtures. In the Utah semi-arid grassland, we took advantage of invasion by Bromus tectorum into long-term plots dominated by either of two native grasses, Hilaria jamesii or Stipa hymenoides. Arbuscular mycorrhizal fungi colonizing roots were characterized with PCR amplification of the ITS region, cloning, and sequencing. We saw a significant effect of the presence of exotic grasses on the diversity of mycorrhizal fungi colonizing native plant roots. In the three native grasses, richness of mycorrhizal fungi decreased; in the native forb at the California site, the number of fungal RFLP patterns increased in the presence of exotics. The exotic grasses also caused the composition of the mycorrhizal community in native roots to shift dramatically both in California, with turnover of Glomus spp., and Utah, with replacement of Glomus spp. by apparently non-mycorrhizal fungi. Invading plants may be able to influence the network of mycorrhizal fungi in soil that is available to natives through either earlier root activity or differential carbon provision compared to natives. Alteration of the soil microbial community by plant invasion can provide a mechanism for both successful invasion and the resulting effects of invaders on the ecosystem. ?? Springer 2006.

Hawkes, C.V.; Belnap, J.; D'Antonio, C.; Firestone, M.K.

2006-01-01

84

Stage-dependent border cell and carbon flow from roots to rhizosphere.  

PubMed

Rising CO(2) levels in the atmosphere have drawn attention to the important role of soil in sequestering carbon. This project goal was to quantify soil carbon deposition associated with border cell release and exudation from root growth zones. Carbon was measured with a Carlo Erba C/N analyzer in soil from the rhizosphere of mature grasses and, in separate experiments, in soil collected around root growth zones. Root border cells in "rhizosphere soil" (silica sand) were counted using a compound microscope after soil sonication and extraction with surfactant. For sand-grown Bromus carinatus, Zea mays, and Cucumis sativus, young seedlings (with roots shorter than 2 cm) released thousands of border cells, while older root tips released only hundreds. For a variety of native annual and perennial grasses and invasive annual grasses (Nassella pulchra, B. carinatus, B. diandrus, B. hordeaceus, Vulpia microstachys, Aegilops triuncialis, Lolium multiflorum, Zea mays), the rhizosphere of mature root systems contained between 18 and 32 ?g C g(-1) sand more than that of the unplanted controls. Spatial analysis of the rhizosphere around the cucumber growth zone confirmed C enrichment there. The root tip provided C to the rhizosphere: 4.6 ?g C in front of the growing tip, with the largest deposition, 20.4 ?g C, to the rhizosphere surrounding the apical 3 mm (root cap/meristem). These numbers from laboratory studies represent the maximum C that might be released during flooding in soils. Scaling up from the organ scale to the field requires a growth analysis to quantify root tip distributions in space and time. PMID:21632368

Odell, Ryan E; Dumlao, Matthew R; Samar, Danial; Silk, Wendy K

2008-04-01

85

Solar forcing of Gulf of California climate during the past 2000??yr suggested by diatoms and silicoflagellates  

USGS Publications Warehouse

High-resolution records of the past 2000??yr are compared in a north-south transect (28?? N to 24?? N) of three cores from the eastern slopes of the Guaymas, Carmen, and Pescadero Basins of the Gulf of California (hereafter referred to as the "Gulf"). Evenly-spaced samples from the varved sediments in each core allow sample resolution ranging from ?????16 to ?????37??yr. Diatoms and silicoflagellates capture the seasonal variation between a late fall to early spring period of high biosiliceous productivity, that is driven by northwest winds, and a summer period of warmer, more stratified waters during which these winds slacken and/or reverse direction (monsoonal flow). As these winds decrease, tropical waters enter the Gulf and spread northward. Individual samples represent a composite of 7 to 23??yr of deposition and are assumed to record the relative dominance of the winter vs. summer floral components. Intervals of enhanced summer incursion of tropical waters, alternating with periods of increased late fall to early spring biosiliceous productivity are recorded in all three cores. Regularly spaced cycles (?????100??yr duration) of Octactis pulchra, a silicoflagellate proxy for lower SST and high productivity, and Azpeitia nodulifera, a tropical diatom, occur between ?????A.D. 400 and ?????1700 in the more nearshore Carmen Basin core, NH01-21 (26.3?? N), suggesting a possible solar influence on coastal upwelling. Cores BAM80 E-17 (27.9?? N) and NH01-26 (24.3?? N) contain longer-duration cycles of diatoms and silicoflagellates. The early part of Medieval Climate Anomaly (?????A.D. 900 to 1200) is characterized by two periods of reduced productivity (warmer SST) with an intervening high productivity (cool) interval centered at ?????A.D. 1050. Reduced productivity and higher SST also characterize the record of the last ?????100 to 200??yr in these cores. Solar variability appears to be driving productivity cycles, as intervals of increased radiocarbon production (sunspot minima) correlate with intervals of enhanced productivity. It is proposed that increased winter cooling of the atmosphere above southwest U.S. during sunspot minima causes intensification of the northwest winds that blow down the Gulf during the late fall to early spring, leading to intensified overturn of surface waters and enhanced productivity. A new silicoflagellate species, Dictyocha franshepardii Bukry, is described and illustrated. ?? 2006 Elsevier B.V. All rights reserved.

Barron, J. A.; Bukry, D.

2007-01-01

86

Seasonal greening of an Arctic ecosystem in response to early snowmelt and climate warming: do plant community responses differ from species responses?  

NASA Astrophysics Data System (ADS)

In the Arctic and around the world, earlier plant growth and a longer growing season are indications that warmer temperatures or other global changes are changing the seasonality of the Earth's ecosystems. These changes in plant life histories have multi-trophic level consequences that affect food webs and biogeochemical cycles. Both the response of the plant community and of individual species can affect food and habitat resources for animals or nutrient resources for microbes. Our aim was to determine if the response of an Arctic plant community differs from individual species responses to climate change. For two years in an early snowmelt and climate warming experiment in moist acidic tussock tundra, we observed the seasonal greening of the ecosystem through near-surface measurements of surface greenness and through direct observations of the timing of plant life history events for five to eight common species that differ in growth form. In 2010 when snowmelt was accelerated by 4 days, earlier snowmelt alone or in combination with climate warming extended the life history of the dominant graminoids (E. vaginatum and C. bigelowii) and willow (S. pulchra) by 3 to 4 days. For these species, new leaf production began earlier, while the timing of senescence was similar to the controls. The effect of earlier snowmelt on the life histories of birch (B. nana) and cranberry (V. vitis-idaea) was less, but warming alone tended to increase life history duration. Warming led to earlier leaf expansion for birch and delayed senescence for cranberry. We found that the onset of greening for the plant community began four days earlier, due to the earlier loss of snow cover, and that warming accelerated the rate of greening. Peak season ended 4 days earlier in response to earlier snowmelt and climate warming, due to earlier senescence by birch. In 2011, our manipulation of the snowpack by increasing energy absorption accelerated snowmelt by 15 days and control plots were snowfree on almost the same date as in 2010. As a result greening began earlier and may have led to more varied effects on life history events among the species. In the Arctic, individual species and the plant community green up as soon as the snow is gone, creating food resources and hiding places for animals and a nutrient sink for available nitrogen. If warming temperatures also cue earlier animal development or arrival, resources should be available for most species. However, an early onset to growth can lead to early senescence for some plant species and shift the timing of peak season for the plant community. Animals that depend on late season resources may be affected, unless they can utilize the plant species for which senescence is delayed.

Steltzer, H.; Weintraub, M. N.; Sullivan, P.; Wallenstein, M. D.; Schimel, J.; Darrouzet-Nardi, A.; Shory, R.; Livensperger, C.; Melle, C.; Segal, A. D.; Daly, K.; Tsosie, T.

2011-12-01

87

Plant Community Responses of Alaskan Arctic Tundra After 14 Years of Experimental Warming and Snow Manipulation  

NASA Astrophysics Data System (ADS)

Emissions of greenhouse gases are expected to raise global mean temperature over the next century by 1.0- 3.5°C. Global warming trends are amplified at high latitudes because heating converts high-albedo (reflective) ice and snow surfaces to dark absorptive surfaces that absorb more solar energy and transfer it to the atmosphere. Furthermore, scientists have argued that ecological responses to this recent climate change will be complex and varied. For example, the warming of the Alaskan Arctic during the past 150 years has accelerated over the last three decades and is expected to increase vegetation productivity in tundra if shrubs become more abundant. Predicted vegetation changes in arctic tundra, because of climate change, have therefore been based on a warmer climate that is either drier or wetter than at present. In order to investigate how tundra vegetation may respond to increases in temperature and snow cover, we used 1m2 open-topped fiberglass chambers (OTC's) combined with large snow fences to artificially warm and modify winter snow regimes of a series of permanent vegetation plots established in Toolik Lake Field Station, Alaska. Fieldwork consisted in measuring the vegetation growth and height of plant species in these plots using the point-frame method. The snow cover and temperature manipulation was done in two ecosystem types, dry heath tundra and moist tussock tundra. The study sheds light on how the vegetation of these two tundra sites has responded after 14 years into the experiment and focuses in changes is species composition, relative abundance, diversity and canopy height. Preliminary results suggest major changes in vegetation composition in both tundra sites over the 14 year sampling period. Changes were more conspicuous in the moist tussock tundra site, where considerable increases in the abundance of the dominant species Betula nana, Eriophorum vaginatum, Salix pulchra and Carex bigelowii were detected consistently throughout the years. Instead, changes in the dry heath tundra show a recent decrease in the dominance of the species Arctostaphylos alpina and Dryas octopetala and an increase in the abundance of the species Louseleuria procumbens. Changes observed in the moist tundra supports the predictions of shrub/graminoid dominated tundra in a warmer global temperature scenario while changes in the dry heath tundra might suggest successional patterns in vegetation composition.

Mercado, J. A.; Gould, W. A.

2008-12-01