35 research outputs found

    Endemicity, Biogeography, Composition, and Community Structure On a Northeast Pacific Seamount

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    The deep ocean greater than 1 km covers the majority of the earth's surface. Interspersed on the abyssal plains and continental slope are an estimated 14000 seamounts, topographic features extending 1000 m off the seafloor. A variety of hypotheses are posited that suggest the ecological, evolutionary, and oceanographic processes on seamounts differ from those governing the surrounding deep sea. The most prominent and oldest of these hypotheses, the seamount endemicity hypothesis (SMEH), states that seamounts possess a set of isolating mechanisms that produce highly endemic faunas. Here, we constructed a faunal inventory for Davidson Seamount, the first bathymetric feature to be characterized as a ‘seamount’, residing 120 km off the central California coast in approximately 3600 m of water (Fig 1). We find little support for the SMEH among megafauna of a Northeast Pacific seamount; instead, finding an assemblage of species that also occurs on adjacent continental margins. A large percentage of these species are also cosmopolitan with ranges extending over much of the Pacific Ocean Basin. Despite the similarity in composition between the seamount and non-seamount communities, we provide preliminary evidence that seamount communities may be structured differently and potentially serve as source of larvae for suboptimal, non-seamount habitats

    Discretized rotation has infinitely many periodic orbits

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    For a fixed k in (-2,2), the discretized rotation on Z^2 is defined by (x,y)->(y,-[x+ky]). We prove that this dynamics has infinitely many periodic orbits.Comment: Revised after referee reports, and added a quantitative statemen

    Symmetry Decomposition of Chaotic Dynamics

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    Discrete symmetries of dynamical flows give rise to relations between periodic orbits, reduce the dynamics to a fundamental domain, and lead to factorizations of zeta functions. These factorizations in turn reduce the labor and improve the convergence of cycle expansions for classical and quantum spectra associated with the flow. In this paper the general formalism is developed, with the NN-disk pinball model used as a concrete example and a series of physically interesting cases worked out in detail.Comment: CYCLER Paper 93mar01

    Role of IP3 Receptors during Early Zebrafish Development.

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    Fluctuations in cytosolic Ca2+ are crucial for a variety of cellular processes including many aspects of development. Mobilization of intracellular Ca2+ stores via the production of inositol trisphosphate (IP3) and the consequent activation of IP3-sensitive Ca2+ channels is a ubiquitous means by which diverse stimuli mediate their cellular effects. Although IP3 receptors have been well studied at fertilization, information regarding their possible involvement during subsequent development is scant. In the present study we examined the role of IP3 receptors in early development of the zebrafish. We report the first molecular analysis of zebrafish IP3 receptors which indicates that, like mammals, the zebrafish genome contains three distinct IP3 receptor genes. mRNA for all isoforms was detectable at differing levels by the 64 cell stage, and IP3-induced Ca2+ transients could be readily generated (by flash photolysis) in a controlled fashion throughout the cleavage period in vivo. Furthermore, we show that early blastula formation was disrupted by pharmacological blockade of IP3 receptors or phospholipase C, by molecular inhibition of the former by injection of IRBIT (IP3 receptor-binding protein released with IP3) and by depletion of thapsigargin-sensitive Ca2+ stores after completion of the second cell cycle. Inhibition of Ca2+ entry or ryanodine receptors, however, had little effect. Our work defines the importance of IP3 receptors during early development of a genetically and optically tractable model vertebrate organism
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