308,566 research outputs found

    Taxonomy of the spring dwelling amphipod Synurella ambulans (Crustacea: Crangonyctidae) in West Russia: with notes on its distribution and ecology

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    This study deals with taxonomic problems of the semi-subterranean crangonyctid amphipod Synurella ambulans (F. Müller, 1846), well-known from various freshwater habitats in Europe. The taxonomy of the species S. ambulans and the generic diagnosis for the genus Synurella are revised. A new synonymy is proposed: Synurella ambulans (F. Müller, 1846) = Synurella ambulans meschtscherica Borutzky, 1929, syn. nov. The affinity with the related groups, distribution and ecology of the species are examined

    Taxonomy of the spring dwelling amphipod Synurella ambulans (Crustacea: Crangonyctidae) in West Russia: with notes on its distribution and ecology

    Get PDF
    This study deals with taxonomic problems of the semi-subterranean crangonyctid amphipod Synurella ambulans (F. Müller, 1846), well-known from various freshwater habitats in Europe. The taxonomy of the species S. ambulans and the generic diagnosis for the genus Synurella are revised. A new synonymy is proposed: Synurella ambulans (F. Müller, 1846) = Synurella ambulans meschtscherica Borutzky, 1929, syn. nov. The affinity with the related groups, distribution and ecology of the species are examined

    Nineteenth-century Ship-based Catches of Gray Whales, Eschrichtius robustus, in the Eastern North Pacific

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    The 19th century commercial ship-based fishery for gray whales, Eschrichtius robustus, in the eastern North Pacific began in 1846 and continued until the mid 1870’s in southern areas and the 1880’s in the north. Henderson identified three periods in the southern part of the fishery: Initial, 1846–1854; Bonanza, 1855–1865; and Declining, 1866–1874. The largest catches were made by “lagoon whaling” in or immediately outside the whale population’s main wintering areas in Mexico—Magdalena Bay, Scammon’s Lagoon, and San Ignacio Lagoon. Large catches were also made by “coastal” or “alongshore” whaling where the whalers attacked animals as they migrated along the coast. Gray whales were also hunted to a limited extent on their feeding grounds in the Bering and Chukchi Seas in summer. Using all available sources, we identified 657 visits by whaling vessels to the Mexican whaling grounds during the gray whale breeding and calving seasons between 1846 and 1874. We then estimated the total number of such visits in which the whalers engaged in gray whaling. We also read logbooks from a sample of known visits to estimate catch per visit and the rate at which struck animals were lost. This resulted in an overall estimate of 5,269 gray whales (SE = 223.4) landed by the ship-based fleet (including both American and foreign vessels) in the Mexican whaling grounds from 1846 to 1874. Our “best” estimate of the number of gray whales removed from the eastern North Pacific (i.e. catch plus hunting loss) lies somewhere between 6,124 and 8,021, depending on assumptions about survival of struck-but-lost whales. Our estimates can be compared to those by Henderson (1984), who estimated that 5,542–5,507 gray whales were secured and processed by ship-based whalers between 1846 and 1874; Scammon (1874), who believed the total kill over the same period (of eastern gray whales by all whalers in all areas) did not exceed 10,800; and Best (1987), who estimated the total landed catch of gray whales (eastern and western) by American ship-based whalers at 2,665 or 3,013 (method-dependent) from 1850 to 1879. Our new estimates are not high enough to resolve apparent inconsistencies between the catch history and estimates of historical abundance based on genetic variability. We suggest several lines of further research that may help resolve these inconsistencies

    A double main sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud

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    We report on HST/ACS photometry of the rich intermediate-age star cluster NGC 1846 in the Large Magellanic Cloud, which clearly reveals the presence of a double main sequence turn-off in this object. Despite this, the main sequence, sub-giant branch, and red giant branch are all narrow and well-defined, and the red clump is compact. We examine the spatial distribution of turn-off stars and demonstrate that all belong to NGC 1846 rather than to any field star population. In addition, the spatial distributions of the two sets of turn-off stars may exhibit different central concentrations and some asymmetries. By fitting isochrones, we show that the properties of the colour-magnitude diagram can be explained if there are two stellar populations of equivalent metal abundance in NGC 1846, differing in age by approximately 300 Myr. The absolute ages of the two populations are ~1.9 and ~2.2 Gyr, although there may be a systematic error of up to +/-0.4 Gyr in these values. The metal abundance inferred from isochrone fitting is [M/H] ~ -0.40, consistent with spectroscopic measurements of [Fe/H]. We propose that the observed properties of NGC 1846 can be explained if this object originated via the tidal capture of two star clusters formed separately in a star cluster group in a single giant molecular cloud. This scenario accounts naturally for the age difference and uniform metallicity of the two member populations, as well as the differences in their spatial distributions.Comment: 9 pages, 8 figures, accepted for publication in MNRAS. A version with full resolution figures may be obtained at http://www.roe.ac.uk/~dmy/papers/MN-07-0441-MJ_rv.ps.gz (postscript) or at http://www.roe.ac.uk/~dmy/papers/MN-07-0441-MJ_rv.pdf (PDF

    How and Why the Marketplace of Ideas Fails

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    It Ain\u27t Etiquette

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    ...I do not condone coarseness at the table, but its adversary, delicacy, has risen to such prominence that if the Duchess of Tweedleborn were to give vent to a belch, no matter how tiny or how Bacchanalian, the scandal would be earth-shaking..

    Observations on web-invasion by the jumping spider Thyene imperialis in Israel (Araneae: Salticidae)

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    Observations on Thyene imperialis (Rossi, 1846) in Israel, Negev desert, invading a web of Cyclosa deserticola Levy, 1998 are reported. The female leapt into the orb-web to catch Cyclosa spiders. Photographs are provided, and a link to additional film material is given
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