Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Vertebrates

  • adult vertebrate
  • different vertebrate
  • ectothermic vertebrate
  • extant vertebrate
  • jawed vertebrate
  • large vertebrate
  • lower vertebrate
  • many vertebrate
  • marine vertebrate
  • other vertebrate
  • small vertebrate
  • terrestrial vertebrate

  • Terms modified by Vertebrates

  • vertebrate brain
  • vertebrate cell
  • vertebrate central nervous system
  • vertebrate class
  • vertebrate development
  • vertebrate embryo
  • vertebrate evolution
  • vertebrate fauna
  • vertebrate genome
  • vertebrate groups
  • vertebrate host
  • vertebrate hosts
  • vertebrate limb
  • vertebrate limb development
  • vertebrate lineage
  • vertebrate model
  • vertebrate nervous system
  • vertebrate neuromuscular junction
  • vertebrate population
  • vertebrate predator
  • vertebrate retina
  • vertebrate species
  • vertebrate system
  • vertebrate taxa
  • vertebrate tissue

  • Selected Abstracts


    EVOLUTION, Issue 4 2009
    Joseph D. DiBattista
    Estimating quantitative genetic parameters ideally takes place in natural populations, but relatively few studies have overcome the inherent logistical difficulties. For this reason, no estimates currently exist for the genetic basis of life-history traits in natural populations of large marine vertebrates. And yet such estimates are likely to be important given the exposure of this taxon to changing selection pressures, and the relevance of life-history traits to population productivity. We report such estimates from a long-term (1995,2007) study of lemon sharks (Negaprion brevirostris) conducted at Bimini, Bahamas. We obtained these estimates by genetically reconstructing a population pedigree (117 dams, 487 sires, and 1351 offspring) and then using an "animal model" approach to estimate quantitative genetic parameters. We find significant additive genetic (co)variance, and hence moderate heritability, for juvenile length and mass. We also find substantial maternal effects for these traits at age-0, but not age-1, confirming that genotype,phenotype interactions between mother and offspring are strongest at birth; although these effects could not be parsed into their genetic and nongenetic components. Our results suggest that human-imposed selection pressures (e.g., size-selective harvesting) might impose noteworthy evolutionary change even in large marine vertebrates. We therefore use our findings to explain how maternal effects may sometimes promote maladaptive juvenile traits, and how lemon sharks at different nursery sites may show "constrained local adaptation." We also show how single-generation pedigrees, and even simple marker-based regression methods, can provide accurate estimates of quantitative genetic parameters in at least some natural systems. [source]


    EVOLUTION, Issue 2 2002
    Nadia A. Chuzhanova
    Abstract Complexity analysis is capable of highlighting those gross evolutionary changes in gene promoter regions (loosely termed "promoter shuffling") that are undetectable by conventional DNA sequence alignment. Complexity analysis was therefore used here to identify the modular components (blocks) of the orthologous ,-globin gene promoter sequences of 22 vertebrate species, from zebrafish to humans. Considerable variation between the ,-globin gene promoters was apparent in terms of block presence/absence, copy number, and relative location. Some sequence blocks appear to be ubiquitous, whereas others are restricted to a specific taxon. Block similarities were also evident between the promoters of the paralogous human ,-like globin genes. It may be inferred that a wide variety of different mutational mechanisms have operated upon the ,-globin gene promoter over evolutionary time. Because these include gross changes such as deletion, duplication, amplification, elongation, contraction, and fusion, as well as the steady accumulation of single base-pair substitutions, it is clear that some redefinition of the term "promoter shuffling" is required. This notwithstanding, and as previously described for the vertebrate growth hormone gene promoter, the modular structure of the ,-globin promoter region and those of its paralogous counterparts have continually been rearranged into new combinations through the alteration, or shuffling, of preexisting blocks. Some of these changes may have had no influence on promoter function, but others could have altered either the level of gene expression or the responsiveness of the promoter to external stimuli. The comparative study of vertebrate ,-globin gene promoter regions described here confirms the generality of the phenomenon of sequence block shuffling and thus supports the view that it could have played an important role in the evolution of differential gene expression. [source]

    A New Jawless Vertebrate from the Middle Devonian of Scotland

    PALAEONTOLOGY, Issue 1 2001
    M. J. Newman
    A new jawless vertebrate, Cornovichthys blaauweni gen. et sp. nov., is described from a single complete specimen from the Achanarras fish bed at Achanarras Quarry in Caithness, northern Scotland. The Achanarras fish bed consists of lacustrine laminites and was deposited in a major deep-water phase of the Orcadian lake during the deposition of the cyclic Caithness Flagstone Group. The Achanarras fish bed is of Middle Devonian (Eifelian) age. The new animal compares closely with Euphanerops, one ofthe Frasnian ,anaspids' (Hyperoartii) of the Escuminac Formation at Miguasha, Quebec, Canada. [source]

    Extent of Nontimber Resource Extraction in Tropical Forests: Accessibility to Game Vertebrates by Hunters in the Amazon Basin

    Carlos A. Peres
    We conducted a basin-wide geographic information system analysis of the nonmotorized accessibility of Amazonian NTFP extraction and estimated the proportion of the Amazon drainage basin within Brazil ( 3.74 million km 2 ) that can be accessed on foot from the nearest navigable river or functional road. We use a long-term series of standardized line-transect vertebrate censuses conducted throughout the region to illustrate the effects of physical accessibility on wildlife densities in terms of hunting pressure as a function of distance from the nearest point of access. Population abundance in large-bodied, prime-target species preferred by game hunters tended to increase at greater distances from the access matrix, whereas small-bodied species ignored by hunters usually showed the reverse trend. In addition, we estimated the proportion of presumably inviolate core areas within nature, extractive, and indigenous reserves of Brazilian Amazonia that are prohibitively remote and unlikely to be overhunted; for instance, only 1.16% of the basin-wide area is strictly protected on paper and is reasonably safe from extractive activities targeted to game vertebrates and other valuable NTFPs. Finally, we discuss the concept of truly undisturbed wildlands in the last major tropical forest regions by distinguishing potentially overharvested areas from those that remain largely or entirely pristine and that maintain viable populations of a full complement of harvest-sensitive species. Resumen: Las actividades de extracción enfocadas en un amplio rango de productos forestales no maderables ( NTFPs ) son omnipresentes en los bosques tropicales. Sin embargo, la extensión de bosques estructuralmente intactos en una determinada región afectada por esta forma de perturbación críptica ha sido escasamente documentada. Realizamos un análisis GIS del acceso no motorizado para la extracción NTFP en el Amazonas y estimamos la proporción de la desembocadura de la cuenca amazónica ( ,3.74 millones de km2 ) a la cual se puede acceder a pie a partir del río navegable o la carretera funcional más cercana. Utilizamos series de censos de vertebrados a largo plazo empleando transectos en línea estandarizados a lo largo de la región para ejemplificar los efectos del acceso físico sobre las densidades de vida silvestre en términos de presión de caza como función de la distancia al punto de acceso más cercano. La abundancia poblacional de especies de cuerpo grande que son blancos preferidos por los cazadores tendió a crecer a mayores distancias de la matriz de acceso, mientras que las especies de cuerpo pequeño ignoradas por los cazadores generalmente muestran la tendencia inversa. Además, estimamos la proporción de áreas medulares presuntamente inviolables dentro de las reservas naturales, extractivas e indígenas del Amazonas brasileño que son prohibitivamente remotas y poco probables de ser sobreexplotadas: por ejemplo, solo el 1.16% del área de la cuenca estrictamente proyectada en papel está razonablemente a salvo de las actividades extractivas de los vertebrados de caza y otras NTFPs valiosas. Finalmente, discutimos el concepto de tierras silvestres verdaderamente no perturbadas en las grandes regiones de bosque tropical restantes diferenciando las áreas potencialmente sobreexplotadas de aquellas que son en su mayor parte o totalmente prístinas y que mantienen poblaciones viables de un complemento total de especies sensibles a la cosecha. [source]

    Performance of Sub-Saharan Vertebrates as Indicator Groups for Identifying Priority Areas for Conservation

    Joslin L. Moore
    Often, these sets of important areas, referred to as priority sets, have been identified through use of data on a single taxon (e.g., birds), which is assumed to act as an indicator for all biodiversity. Using a database of the distributions of 3882 vertebrate species in sub-Saharan Africa, we conducted one of very few large-scale tests of this assumption. We used six potential indicator groups,birds, mammals, amphibians, snakes, threatened birds, and threatened mammals,to find priority sets of 200 areas that best represent the species in that group. Priority sets of grid cells designed to maximize representation of a single indicator group captured 83,93% of species in the other groups. This high degree of representation is consistent with observed high levels of overlap in the patterns of distribution of species in different groups. Those species of highest conservation interest were more poorly represented, however, with only 75,88% of other groups' threatened species and 63,76% of other groups' narrow-range species represented in the priority sets. We conclude that existing priority sets based on indicator groups provide a pragmatic basis for the immediate assessment of priorities for conservation at a continental scale. However, complete and efficient representation,especially of narrow-range species,will not be achieved through indicator groups alone. Therefore, priority-setting procedures must remain flexible so that new areas important for other taxa can be incorporated as data become available. Resumen: La meta de la identificación de prioridades globales y continentales de conservación es la identificación de áreas particularmente valiosas para la conservación en las cuales enfocar esfuerzos más detallados. A menudo, estos conjuntos de áreas importantes (referidas como conjuntos prioritarios) han sido identificados utilizando datos de un solo taxón (e. g. aves), el cual se supone que actúa como indicador de toda la biodiversidad. Utilizando una base de datos de la distribución de 3882 especies de vertebrados en África sub-Sahara, realizamos una de las pocas pruebas a gran escala de este supuesto. Utilizamos seis grupos de indicadores potenciales (aves, mamíferos, anfibios, serpientes, aves amenazadas y mamíferos amenazados ) para encontrar conjuntos prioritarios de 200 áreas que mejor representan las especies de ese grupo. Conjuntos prioritarios de celdas matriciales diseñadas para maximizar la representatividad de un grupo indicador capturaron 83,93% de las especies de los otros grupos. Este alto grado de representatividad es consistente con los altos niveles de superposición observados en los patrones de distribución de especies en los diferentes grupos. Sin embargo, las especies de mayor interés para la conservación estaban poco representadas, con solo 75,88% de las especies amenazadas de otros grupos y 63,76% de las especies de distribución restringida de otros grupos representados en los conjuntos prioritarios. Concluimos que los conjuntos prioritarios existentes, basados en grupos indicadores, proporcionan una base pragmática para la evaluación inmediata de las prioridades de conservación a escala continental. Sin embargo, no se logrará la representación completa y eficiente,especialmente de especies de distribución restringida,solo con grupos indicadores. Por lo tanto, los procedimientos de definición de prioridades deben permanecer flexibles para que se puedan incorporar nuevas áreas importantes para otros taxones a medida que se obtienen los datos. [source]

    Synergistic Effects of Subsistence Hunting and Habitat Fragmentation on Amazonian Forest Vertebrates

    Carlos A. Peres
    These effects are likely to be considerably aggravated by forest fragmentation because fragments are more accessible to hunters, allow no (or very low rates of ,) recolonization from nonharvested source populations, and may provide a lower-quality resource base for the frugivore-granivore vertebrate fauna. I examined the likelihood of midsized to large-bodied bird and mammal populations persisting in Amazonian forest fragments of variable sizes whenever they continue to be harvested by subsistence hunters in the aftermath of isolation. I used data from a comprehensive compilation of game-harvest studies throughout Neotropical forests to estimate the degree to which different species and populations have been overharvested and then calculated the range of minimum forest areas required to maintain a sustainable harvest. The size distribution of 5564 Amazonian forest fragments,estimated from Landsat images of six regions of southern and eastern Brazilian Amazonia,clearly shows that these are predominantly small and rarely exceed 10 ha, suggesting that persistent overhunting is likely to drive most midsized to large vertebrate populations to local extinction in fragmented forest landscapes. Although experimental studies on this negative synergism remain largely unavailable, the prospect that increasingly fragmented Neotropical forest regions can retain their full assemblages of avian and mammalian species is unlikely. Resumen: La cacería de subsistencia tiene efectos negativos profundos sobre la diversidad de especies, la biomasa y estructura de las comunidades de vertebrados en bosques de la Amazonía que de otra forma están poco perturbadas. Estos efectos se agravan considerablemente por la fragmentación del bosque porque los fragmentos son más accesibles a los cazadores, no permiten la recolonización por poblaciones no cazadas o disminuyen las tasas de recolonizacíon y pueden proporcionar una base de recursos de menor calidad para la fauna de vertebrados frugívoro-granívoros. Examiné la posibilidad de persistencia de poblaciones de aves y mamíferos medianos a grandes en fragmentos de bosque de tamaño variable si continúan sujetos a la cacería de subsistencia como una consecuencia del aislamiento. Utilicé datos de una compilación extensiva de estudios de cacería en bosques neotropicales para estimar el grado en que diferentes especies y poblaciones han sido sobre explotadas y calculé el área de bosque minima requerida para mantener una cosecha sostensible. La distribucíon de tamaños de 5564 fragmentos de bosque amazónica, estimado a partir de imágues de Landsat de seis regiones del sur y del esté de la Amazonía brasileña indica claramente que estos fragmentós son principalmente pegueños y que rara vez exceden las lolta, lo que sugiere que la sobre cacería persistente probablemente lleve a la extincíon local de poblaciones de vertebrados de tamaño mediano a grande en paisajes boscosos fragmentados. Aunque estudios experimentales de este sinergismo negativo no están disponibles, la perspectiva de que las regiones neotropicales cada vez más fragmentadas, puedan retener las comunidades completas de aves y mamíferos poco es probable. [source]

    Talin2 is induced during striated muscle differentiation and is targeted to stable adhesion complexes in mature muscle

    CYTOSKELETON, Issue 3 2007
    Melissa A. Senetar
    Abstract The cytoskeletal protein talin serves as an essential link between integrins and the actin cytoskeleton in several similar, but functionally distinct, adhesion complexes, including focal adhesions, costameres, and intercalated disks. Vertebrates contain two talin genes, TLN1 and TLN2, but the different roles of Talin1 and Talin2 in cell adhesion are unclear. In this report we have analyzed Talin1 and Talin2 in striated muscle. Using isoform-specific antibodies, we found that Talin2 is highly expressed in mature striated muscle. Using mouse C2C12 cells and primary human skeletal muscle myoblasts as models of muscle differentiation, we show that Talin1 is expressed in undifferentiated myoblasts and that Talin2 expression is upregulated during muscle differentiation at both the mRNA and protein levels. We have also identified regulatory sequences that may be responsible for the differential expression of Talin1 and Talin2. Using GFP-tagged Talin1 and Talin2 constructs, we found that GFP-Talin1 targets to focal adhesions while GFP-Talin2 targets to abnormally large adhesions in myoblasts. We also found that ectopic expression of Talin2 in myoblasts, which do not contain appreciable levels of Talin2, dysregulates the actin cytoskeleton. Finally we demonstrate that Talin2, but not Talin1, localizes to costameres and intercalated disks, which are stable adhesions required for the assembly of mature striated muscle. Our results suggest that Talin1 is the primary link between integrins and actin in dynamic focal adhesions in undifferentiated, motile cells, but that Talin2 may serve as the link between integrins and the sarcomeric cytoskeletonin stable adhesion complexes in mature striated muscle. Cell Motil. Cytoskeleton 2007. © 2006 Wiley-Liss, Inc. [source]

    Great northern researchers: discoverers of the earliest Palaeozoic vertebrates

    ACTA ZOOLOGICA, Issue 2009
    Hans-Peter Schultze
    Abstract The lives and works of Dr Elga Mark-Kurik and Dr Valentina Karatajute-Talimaa, Estonian and Lithuanian palaeontologists, respectively, are presented as part of their celebration at the 11th Symposium on Early/Lower Vertebrates at Uppsala. Both graduated from the university of their home town, Tartu and Vilnius, respectively. Elga became a Researcher at the Institute of Geology of the Estonian S.S.R. Academy of Sciences, in Tallinn, whereas Valentina worked for the Institute of Geology, Vilnius. Both were mentored by D. V. Obruchev of Moscow. Elga chose placoderms and psammosteid heterostracans as main research objects. Valentina also began with whole fish, antiarch placoderms, but then chose fish microfossils with W. Gross as mentor and discovered the oldest chondrichthyans. Both work as palaeobiologists understanding the implications of their fossils for functional interpretation and palaeogeography; their main contribution is in biostratigraphy (over 50% of their publications). In 1976 Elga organized the 1st Middle Palaeozoic Fossil Fish Symposium in Tallinn. The co-operation of young eastern and western palaeoichthyologists begun there culminating in the 1990s with the international research effort of the UNESCO-IUGS International Geological Correlation Programmes (328, 406 and 491). [source]

    Vegetationskundliche Untersuchungen in der Borzongijn- und Galbyn-Gobi (Ömnögov Aimak, Mongolei)

    FEDDES REPERTORIUM, Issue 5-6 2006
    W. Hilbig Dr.
    Während der im August 2005 von Zoologen der Georg-August-Universität Göttingen durchgeführten 4. "Gobi Desert Vertebrates"-Expedition in den Ömnögov Aimak der Mongolei, an der wir teilnehmen konnten, wurden von uns Vegetationsuntersuchungen in den pflanzengeographischen Bezirken Ost-Gobi und Ala,an-Gobi durchgeführt. Dabei widmeten wir uns im Wesentlichen den weitverbreiteten zonalen Pflanzengesellschaften der Wüsten und Halbwüsten. Aber auch der Vegetation der grundwassernahen Standorte und der anthropogenen Vegetation wurde Beachtung geschenkt. Einige floristische Neunachweise für die genannten Bezirke konnten erbracht werden. Solanum physalifolium wurde in der Mongolei neu gefunden. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Geobotanical research in the Borzongiyn- and Galbyn-Gobi (Ömnögov Aimak, Mongolia) In August 2005 we joint the 4th "Gobi Desert Vertebrates"-Expedition of zoologists from the Georg-August-University Göttingen to the Ömnögov Aimak of Mongolia. During the expedition we made geobotanical studies in the plantgeographic regions East-Gobi and Alashan-Gobi. Generally we worked on the widespread zonal plant communities of desert and semi-desert. But consideration was paid also to the vegetation of habitats close to groundwater and to the anthropogenic vegetation. We could find some new additions to the flora of the above mentioned regions. Solanum physalifolium was found new for Mongolia. [source]

    Carotenoid coloration in great black-backed gull Larus marinus reflects individual quality

    Kai O. Kristiansen
    Carotenoids are a large group of biochemicals, with similar properties, synthesised by bacteria, fungi, algae and plants. Vertebrates obtain these biologically active pigments through the diet, and they are a disproportionately common component of animal colour signals and play important roles in immune functions and as antioxidants. Carotenoids are believed to be a limited resource and because of the trade-off between allocation of carotenoids to signals and to other functions, carotenoid based signals are often thought to be handicap signals. The purpose of this study was to investigate the signalling potential of carotenoid-based tissue coloration in the great black-backed gull Larus marinus. The intensity of carotenoid-based coloration in bill, gape and eye-ring coloration was investigated in relation to body condition, reproductive parameters, levels of immune activity, and sexual dimorphism. In males there was a positive relationship between colour intensity and body condition, but in females no such relationship was found. However, females with high colour intensity had larger eggs and clutches. Additionally, females with high red scores tended to have high density of circulating lymphocytes. There was no sexual dimorphism in coloration and there was a negative relationship between colour intensity and sampling time, which indicates that this coloration is most intensely expressed early in the breeding season. The results in this study suggest that carotenoid-based coloration in great black-backed gull are partly condition dependent and reveal information about individual quality in both males an females. Hence, it might have evolved as an important signal for assessing the quality of potential mates. [source]

    Taphonomy of Child-Sized Remains: A Study of Scattering and Scavenging in Virginia, USA,

    Robert J. Morton M.S.
    ABSTRACT: Child-sized pig carcasses (Sus scrofa) were placed in surface deposit and buried scenarios in a wooded area of Virginia from May 1998 through December 2000, to examine the taphonomic effects of decompositional changes, predator scavenging, and the extent of remains scattering. Changes were observed through on-site examination, charting of remains, and recorded video imaging. Analysis of data revealed that utilization of corpses as food sources by vertebrates was dependent upon invertebrate colonization. Vertebrates avoided feeding on the corpses while invertebrate colonization was active, and would feed before invertebrates successfully colonized a corpse, or would wait until the invertebrate populations migrated away from the corpse. Among vertebrates, there was no apparent succession order for the animals utilizing the remains as a food source. Different vertebrates would feed at different times based upon diurnal or nocturnal predilection. Analysis noted an accidental cooperative relationship between the invertebrates and vertebrates scavenging on the corpses. Certain vertebrates gained access to the internal tissues by utilizing openings in the corpses caused by invertebrate and other vertebrate scavenging. Alternately, carrion-frequenting insects were afforded access to previously inaccessible colonization sites as a result of scavenging vertebrate activities. [source]

    Evolution and Biogeography of Australasian Vertebrates

    AUSTRAL ECOLOGY, Issue 1 2008
    No abstract is available for this article. [source]

    Seed Dispersal of the Palm Syagrus romanzoffiana by Tapirs in the Semi-deciduous Atlantic Forest of Argentina

    BIOTROPICA, Issue 4 2009
    Mariano I. Giombini
    ABSTRACT Vertebrates play a fundamental role in the dispersal of Neotropical trees, generating different seed shadows according to their physical and behavioral features. Tapirs are capable of consuming great quantities of large fruits, and they defecate seeds far from parent trees. For instance, intact seeds of the palm Syagrus romanzoffiana have been found in tapir dung piles in the Atlantic Forest of southeastern Brazil, suggesting that tapirs effectively disperse this species. However, recruitment was not examined therein. We studied tapir endozoochory of large and medium seeds in the semi-deciduous Atlantic Forest of Argentina by examining dung piles found within Iguazu National Park. We recorded dung-pile positions to evaluate the spatial distribution. We also counted the number of juveniles in 2 × 2 m quadrats placed on old dung piles in latrines, beneath adults and in random sites to estimate recruitment levels. Syagrus romanzoffiana seeds were present in 98 percent of dung piles, averaging >200 seeds/dung pile, indicating that this species constitutes the main fruit component in the tapir's diet. Dung piles showed a clumped deposition pattern reflecting the use of latrines. Juvenile recruitment in latrines was 21 times higher than that of under-adult sites and 500 times greater than in random sites, and correlated with the frequency of use of the areas. We concluded that the lowland tapir is a major disperser of S. romanzoffiana. Given that this palm can be considered a keystone species, a disruption of this interaction might affect the entire community of frugivores in the long term. [source]

    The , isotypes of tubulin in neuronal differentiation,

    CYTOSKELETON, Issue 7 2010
    Jiayan Guo
    Abstract The differences among the vertebrate , isotypes of tubulin are highly conserved in evolution, suggesting that they have functional significance. To address this, we have used differentiating neuroblastoma cells as a model system. These cells express the ,I, ,II, and ,III isotypes. Although there is no difference prior to differentiation, a striking difference is seen after differentiation. Both ,I and ,III occur in cell bodies and neurites, while ,II occurs mostly in neurites. Knocking down ,I causes a large decrease in cell viability while silencing ,II and ,III does not. Knocking down ,II causes a large decrease in neurite outgrowth without affecting viability. Knocking down ,III has little effect on neurite outgrowth and only decreases viability if cells are treated with glutamate and glycine, a combination known to generate free radicals and reactive oxygen species. It appears, therefore, that ,I is required for cell viability, ,II for neurite outgrowth and ,III for protection against free radicals and reactive oxygen species. © 2010 Wiley-Liss, Inc. [source]

    Kinesin-5 is not essential for mitotic spindle elongation in Dictyostelium

    CYTOSKELETON, Issue 11 2008
    Irina Tikhonenko
    Abstract The proper assembly and operation of the mitotic spindle is essential to ensure the accurate segregation of chromosomes and to position the cytokinetic furrow during cell division in eukaryotes. Not only are dynamic microtubules required but also the concerted actions of multiple motor proteins are necessary to effect spindle pole separation, chromosome alignment, chromatid segregation, and spindle elongation. Although a number of motor proteins are known to play a role in mitosis, there remains a limited understanding of their full range of functions and the details by which they interact with other spindle components. The kinesin-5 (BimC/Eg5) family of motors is largely considered essential to drive spindle pole separation during the initial and latter stages of mitosis. We have deleted the gene encoding the kinesin-5 member in Dictyostelium, (kif13), and find that, in sharp contrast with results found in vertebrate, fly, and yeast organisms, kif13, cells continue to grow at rates indistinguishable from wild type. Phenotype analysis reveals a slight increase in spindle elongation rates in the absence of Kif13. More importantly, there is a dramatic, premature separation of spindle halves in kif13, cells, suggesting a novel role of this motor in maintaining spindle integrity at the terminal stages of division. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source]

    Conserved RARE localization in amphioxus Hox clusters and implications for Hox code evolution in the vertebrate neural crest

    Hiroshi Wada
    Abstract The Hox code in the neural crest cells plays an important role in the development of the complex craniofacial structures that are characteristic of vertebrates. Previously, 3, AmphiHox1 flanking region has been shown to drive gene expression in neural tubes and neural crest cells in a retinoic acid (RA)-dependent manner. In the present study, we found that the DR5-type RA response elements located at the 3, AmphiHox1 flanking region of Branchiostoma floridae are necessary and sufficient to express reporter genes in both the neural tube and neural crest cells of chick embryos, specifically at the post-otic level. The DR5 at the 3, flanking region of chick Hoxb1 is also capable of driving the same expression in chick embryos. We found that AmphiHox3 possesses a DR5-type RARE in its 5, flanking region, and this drives an expression pattern similar to the RARE element found in the 3, flanking region of AmphiHox1. Therefore, the location of these DR5-type RAREs is conserved in amphioxus and vertebrate Hox clusters. Our findings demonstrate that conserved RAREs mediate RA-dependent regulation of Hox genes in amphioxus and vertebrates, and in vertebrates this drives expression of Hox genes in both neural crest and neural tube. This suggests that Hox expression in vertebrate neural crest cells has evolved via the co-option of a pre-existing regulatory pathway that primitively regulated neural tube (and possibly epidermal) Hox expression. Developmental Dynamics 235:1522,1531, 2006. © 2006 Wiley-Liss, Inc. [source]

    Frontal nasal prominence expression driven by Tcfap2a relies on a conserved binding site for STAT proteins

    Amy L. Donner
    Abstract The AP-2 transcription factor family is linked with development of the head and limbs in both vertebrate and invertebrate species. Recent evidence has also implicated this gene family in the evolution of the neural crest in chordates, a critical step that allowed the development and elaboration of the vertebrate craniofacial skeleton. In mice, the inappropriate embryonic expression of one particular AP-2 gene, Tcfap2a, encoding AP-2,, results in multiple developmental abnormalities, including craniofacial and limb defects. Thus, Tcfap2a provides a valuable genetic resource to analyze the regulatory hierarchy responsible for the evolution and development of the face and limbs. Previous studies have identified a 2-kilobase intronic region of both the mouse and human AP-2, locus that directs expression of a linked LacZ transgene to the facial processes and the distal mesenchyme of the limb bud in transgenic mice. Further analysis identified two highly conserved regions of ,200,400 bp within this tissue-specific enhancer. We have now initiated a transgenic and biochemical analysis of the most important of these highly conserved regions. Our analysis indicates that although the sequences regulating face and limb expression have been integrated into a single enhancer, different cis -acting sequences ultimately control these two expression domains. Moreover, these studies demonstrate that a conserved STAT binding site provides a major contribution to the expression of Tcfap2a in the facial prominences. Developmental Dynamics 235:1358,1370, 2006. © 2006 Wiley-Liss, Inc. [source]

    Genome-wide identification of female-enriched genes in zebrafish

    Chaoming Wen
    Abstract Characteristic differences in morphology, physiology, and behavior between a male and female are correlated to the differential selection of sex-dependent transcriptomes. By using a cDNA array carrying ,9,000 zebrafish unique genes, we identified a group of genes whose expression are enriched in the female fish. A subset of these genes have been confirmed and further grouped as egg-enriched genes, as both somatic- and egg-enriched genes or as somatic-enriched genes by means of RNA gel blot hybridization. Most importantly, a significant proportion of these genes are either functionally unknown or are novel genes. Thus, future studies of this group of genes will help us greatly to understand more about sex-determination and sex-related physiology and behavior. In addition, comparison of zebrafish female-enriched genes with that in Drosophila, we found that only germline genes are shared between vertebrate and invertebrate, suggesting that the process of oogenesis is highly conserved during the evolution. Developmental Dynamics 232:171,179, 2005. © 2004 Wiley-Liss, Inc. [source]

    Adult neurogenesis in the crayfish brain: Proliferation, migration, and possible origin of precursor cells

    Yi Zhang
    Abstract The birth of new neurons and their incorporation into functional circuits in the adult brain is a characteristic of many vertebrate and invertebrate organisms, including decapod crustaceans. Precursor cells maintaining life-long proliferation in the brains of crayfish (Procambarus clarkii, Cherax destructor) and clawed lobsters (Homarus americanus) reside within a specialized niche on the ventral surface of the brain; their daughters migrate to two proliferation zones along a stream formed by processes of the niche precursors. Here they divide again, finally producing interneurons in the olfactory pathway. The present studies in P. clarkii explore (1) differential proliferative activity among the niche precursor cells with growth and aging, (2) morphological characteristics of cells in the niche and migratory streams, and (3) aspects of the cell cycle in this lineage. Morphologically symmetrical divisions of neuronal precursor cells were observed in the niche near where the migratory streams emerge, as well as in the streams and proliferation zones. The nuclei of migrating cells elongate and undergo shape changes consistent with nucleokinetic movement. LIS1, a highly conserved dynein-binding protein, is expressed in cells in the migratory stream and neurogenic niche, implicating this protein in the translocation of crustacean brain neuronal precursor cells. Symmetrical divisions of the niche precursors and migration of both daughters raised the question of how the niche precursor pool is replenished. We present here preliminary evidence for an association between vascular cells and the niche precursors, which may relate to the life-long growth and maintenance of the crustacean neurogenic niche. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source]

    Drosophila neuromuscular synapse assembly and function require the TGF-, type I receptor saxophone and the transcription factor Mad

    Joel M. Rawson
    Abstract Transforming growth factor-,s (TGF-,) comprise a superfamily of secreted proteins with diverse functions in patterning and cell division control. TGF-, signaling has been implicated in synapse assembly and plasticity in both vertebrate and invertebrate systems. Recently, wishful thinking, a Drosophila gene that encodes a protein related to BMP type II receptors, has been shown to be required for the normal function and development of the neuromuscular junction (NMJ). These findings suggest that a TGF-,-related ligand activates a signaling cascade involving type I and II receptors and the Smad family of transcription factors to orchestrate the assembly of the NMJ. Here we demonstrate that the TGF-, type I receptor Saxophone and the downstream transcription factor Mothers against dpp (Mad) are essential for the normal structural and functional development of the Drosophila NMJ, a synapse that displays activity-dependent plasticity. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 134,150, 2003 [source]

    Integrating highly diverse invertebrates into broad-scale analyses of cross-taxon congruence across the Palaearctic

    ECOGRAPHY, Issue 6 2009
    Andreas Schuldt
    Our knowledge on broad-scale patterns of biodiversity, as a basis for biogeographical models and conservation planning, largely rests upon studies on the spatial distribution of vertebrates and plants, neglecting large parts of the world's biodiversity. To reassess the generality of these patterns and better understand spatial diversity distributions of invertebrates, we analyzed patterns of species richness and endemism of a hyperdiverse insect taxon, carabid beetles (ca 11 000 Palaearctic species known), and its cross-taxon congruence with well-studied vertebrates (amphibians, reptiles) and plants across 107,units of the Palaearctic. Based on species accumulation curves, we accounted for completeness of the carabid data by separately examining the western (well-sampled) and eastern (partly less well-sampled) Palaearctic and China (deficient data). For the western Palaearctic, we highlight overall centers of invertebrate, vertebrate and plant diversity. Species richness and endemism of carabids were highly correlated with patterns of especially plant and amphibian diversity across large parts of the Palaearctic. For the well-sampled western Palaearctic, hotspots of diversity integrating invertebrates were located in Italy, Spain and Greece. Only analysis of Chinese provinces yielded low congruence between carabids and plants/vertebrates. However, Chinese carabid diversity is only insufficiently known and China features the highest numbers of annual new descriptions of carabids in the Palaearctic. Even based on the incomplete data, China harbors at least 25% of all Palaearctic carabid species. Our study shows that richness and endemism patterns of highly diverse insects can exhibit high congruence with general large scale patterns of diversity inferred from plants/vertebrates and that hotspots derived from the latter can also include a high diversity of invertebrates. In this regard, China qualifies as an outstanding multi-taxon hotspot of diversity, requiring intense biodiversity research and conservation effort. Our findings extend the limited knowledge on broad-scale invertebrate distributions and allow for a better understanding of diversity patterns across a larger range of the world's biodiversity than usually considered. [source]

    Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

    1. Predation-exclusion experiments have highlighted that top-down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. 2. We conducted 1-year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. 3. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant-excluded than in control trees, whereas only dermapterans were more abundant in bird-excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. 4. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator,prey system. [source]

    Predation by an exotic lizard, Anolis sagrei, alters the ant community structure in betelnut palm plantations in southern Taiwan

    Abstract 1.,Predators can affect prey directly by reducing prey abundance and indirectly by altering behavioural patterns of prey. From previous studies, there is little evidence that ant community structure is affected by vertebrate predation. 2.,Researchers tend to consider the interactions between vertebrate predators and ants to be weak. The present study examined the impact of the exotic invasive lizard, Anolis sagrei, on the ant community structure by manipulating the density of lizards within enclosures. The natural density of A. sagrei in the field was surveyed and used as the stocking density rate in the lizard-present sub-enclosures. 3.,Before the lizard density was manipulated, there was no difference in the ant diversity between sub-enclosures. After the lizard density manipulation, the ant diversity in sub-enclosures with A. sagrei present was significantly different from that of enclosures where the lizards were absent, although the overall ant abundance did not differ significantly. 4.,The ant diversity difference was generated by a significant reduction of the ant species Pheidole fervens in sub-enclosures with A. sagrei present. Such an abundance change might be the result of direct predation by the lizards, or it might be generated by a foraging site shift by this ant. 5.,The results of this study thus demonstrated that the invasion of an exotic vertebrate can significantly alter the community structure of ants, perhaps through the combined direct and indirect effects of lizards on ants. [source]

    Informed dispersal, heterogeneity in animal dispersal syndromes and the dynamics of spatially structured populations

    ECOLOGY LETTERS, Issue 3 2009
    Jean Clobert
    Abstract There is accumulating evidence that individuals leave their natal area and select a breeding habitat non-randomly by relying upon information about their natal and future breeding environments. This variation in dispersal is not only based on external information (condition dependence) but also depends upon the internal state of individuals (phenotype dependence). As a consequence, not all dispersers are of the same quality or search for the same habitats. In addition, the individual's state is characterized by morphological, physiological or behavioural attributes that might themselves serve as a cue altering the habitat choice of conspecifics. These combined effects of internal and external information have the potential to generate complex movement patterns and could influence population dynamics and colonization processes. Here, we highlight three particular processes that link condition-dependent dispersal, phenotype-dependent dispersal and habitat choice strategies: (1) the relationship between the cause of departure and the dispersers' phenotype; (2) the relationship between the cause of departure and the settlement behaviour and (3) the concept of informed dispersal, where individuals gather and transfer information before and during their movements through the landscape. We review the empirical evidence for these processes with a special emphasis on vertebrate and arthropod model systems, and present case studies that have quantified the impacts of these processes on spatially structured population dynamics. We also discuss recent literature providing strong evidence that individual variation in dispersal has an important impact on both reinforcement and colonization success and therefore must be taken into account when predicting ecological responses to global warming and habitat fragmentation. [source]

    Scale dependence of the correlation between human population presence and vertebrate and plant species richness

    ECOLOGY LETTERS, Issue 1 2007
    Marco Pautasso
    Abstract Human presence is generally negatively related to species richness locally, but the relationship is positive at coarse scales. An increase in the strength of the latter correlation with increasing study resolution has been documented within studies, but it is not known whether such a scale dependence is present across different studies. We test this with data on the spatial co-occurrence of human beings and the species richness of plants and vertebrates from a continuum of scales. The correlation coefficient between human presence and species richness is positively related to study grain and extent. The correlation turns from positive to negative below a study grain of c. 1 km and below a study extent of c. 10 000 km2. The broad-scale positive correlation between human presence and species richness suggests that people have preferentially settled and generally flourished in areas of high biodiversity and/or have contributed to it with species introductions and habitat diversification. The scale dependency of the correlation between people and biodiversity's presence emphasizes the importance of the preservation of green areas in densely populated regions. [source]

    The evolutionary ecology of Plasmodium

    ECOLOGY LETTERS, Issue 9 2003
    R. E. L. Paul
    Abstract Plasmodium, the aetiological agent of malaria, imposes a substantial public health burden on human society and one that is likely to deteriorate. Hitherto, the recent Darwinian medicine movement has promoted the important role evolutionary biology can play in issues of public health. Recasting the malaria parasite two-host life cycle within an evolutionary framework has generated considerable insight into how the parasite has adapted to life within both vertebrate and insect hosts. Coupled with the rapid advances in the molecular basis to host,parasite interactions, exploration of the evolutionary ecology of Plasmodium will enable identification of key steps in the life cycle and highlight fruitful avenues of research for developing malaria control strategies. In addition, elucidating the extent to which Plasmodium can respond to short- and long-term changes in selection pressures, i.e. its adaptive capacity, is even more crucial in predicting how the burden of malaria will alter with our rapidly evolving ecology. [source]

    Abnormalities in sexual development of the amphipod Gammarus pulex (L.) found below sewage treatment works

    Melanie Yvette Gross
    Abstract Increasing numbers of widely used industrial, agricultural, and natural chemicals are known to elicit endocrine-disrupting effects in a wide range of vertebrate and invertebrate species. The objective of this study was to determine whether the sexual development of the freshwater crustacean Gammarus pulex (L.) was affected below sewage treatment works (STW) previously known to contain endocrine-disrupting chemicals in their effluent. The gonadal structure, external sexual characteristics, and size of gammarids from exposed sites were compared to those of gammarids from a reference site. No significant difference was found in the gonadal structure of males collected below two STW. However, a highly significant number of females collected from a site known to elicit high estrogenic responses in vertebrates displayed an abnormal structure of oocytes in vitellogenesis. Body size was significantly shorter and male/female size differential was significantly reduced below one of the STW. Analysis of gnathopod and genital papillae length data suggests that different allometric relationships of these organs to body size exist between sample sites. [source]

    A novel role for polyamines in adult neurogenesis in rodent brain

    Jordane Malaterre
    Abstract Although neurogenesis in the adult is known to be regulated by various internal cues such as hormones, growth factors and cell-adherence molecules, downstream elements underlying their action at the cellular level still remain unclear. We previously showed in an insect model that polyamines (putrescine, spermidine and spermine) play specific roles in adult brain neurogenesis. Here, we demonstrate their involvement in the regulation of secondary neurogenesis in the rodent brain. Using neurosphere assays, we show that putrescine addition stimulates neural progenitor proliferation. Furthermore, in vivo depletion of putrescine by specific and irreversible inhibition of ornithine decarboxylase, the first key enzyme of the polyamine synthesis pathway, induces a consistent decrease in neural progenitor cell proliferation in the two neurogenic areas, the dentate gyrus and the subventricular zone. The present study reveals common mechanisms underlying birth of new neurons in vertebrate and invertebrate species. [source]


    EVOLUTION, Issue 2 2002
    Nadia A. Chuzhanova
    Abstract Complexity analysis is capable of highlighting those gross evolutionary changes in gene promoter regions (loosely termed "promoter shuffling") that are undetectable by conventional DNA sequence alignment. Complexity analysis was therefore used here to identify the modular components (blocks) of the orthologous ,-globin gene promoter sequences of 22 vertebrate species, from zebrafish to humans. Considerable variation between the ,-globin gene promoters was apparent in terms of block presence/absence, copy number, and relative location. Some sequence blocks appear to be ubiquitous, whereas others are restricted to a specific taxon. Block similarities were also evident between the promoters of the paralogous human ,-like globin genes. It may be inferred that a wide variety of different mutational mechanisms have operated upon the ,-globin gene promoter over evolutionary time. Because these include gross changes such as deletion, duplication, amplification, elongation, contraction, and fusion, as well as the steady accumulation of single base-pair substitutions, it is clear that some redefinition of the term "promoter shuffling" is required. This notwithstanding, and as previously described for the vertebrate growth hormone gene promoter, the modular structure of the ,-globin promoter region and those of its paralogous counterparts have continually been rearranged into new combinations through the alteration, or shuffling, of preexisting blocks. Some of these changes may have had no influence on promoter function, but others could have altered either the level of gene expression or the responsiveness of the promoter to external stimuli. The comparative study of vertebrate ,-globin gene promoter regions described here confirms the generality of the phenomenon of sequence block shuffling and thus supports the view that it could have played an important role in the evolution of differential gene expression. [source]

    The origin of the endothelial cells: an evo-devo approach for the invertebrate/vertebrate transition of the circulatory system

    R. Muñoz-Chápuli
    Summary Circulatory systems of vertebrate and invertebrate metazoans are very different. Large vessels of invertebrates are constituted of spaces and lacunae located between the basement membranes of endodermal and mesodermal epithelia, and they lack an endothelial lining. Myoepithelial differentation of the coelomic cells covering hemal spaces is a frequent event, and myoepithelial cells often form microvessels in some large invertebrates. There is no phylogenetic theory about the origin of the endothelial cells in vertebrates. We herein propose that endothelial cells originated from a type of specialized blood cells, called amoebocytes, that adhere to the vascular basement membrane. The transition between amoebocytes and endothelium involved the acquisition of an epithelial phenotype. We suggest that immunological cooperation was the earliest function of these protoendothelial cells. Furthermore, their ability to transiently recover the migratory, invasive phenotype of amoebocytes (i.e., the angiogenic phenotype) allowed for vascular growth from the original visceral areas to the well-developed somatic areas of vertebrates (especially the tail, head, and neural tube). We also hypothesize that pericytes and smooth muscle cells derived from myoepithelial cells detached from the coelomic lining. As the origin of blood cells in invertebrates is probably coelomic, our hypothesis relates the origin of all the elements of the circulatory system with the coelomic wall. We have collected from the literature a number of comparative and developmental data supporting our hypothesis, for example the localization of the vascular endothelial growth factor receptor-2 ortholog in hemocytes of Drosophila or the fact that circulating progenitors can differentiate into endothelial cells even in adult vertebrates. [source]