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排序方式: 共有184条查询结果,搜索用时 15 毫秒
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Favella panamensis Kofoid and Campbell, 1929 is seasonally abundant in meso- to polyhaline waters of Chesapeake Bay and Indian River, Florida, USA, where it reaches densities of 103 cells l-1. During the summers of 1986–1992. F. panamensis populations of the two estuaries were commonly infected by the parasitic dinoflagellate Duboscquella aspida Cachon, 1964. The intracellular phase of the parasite reached maturity in 21 h (30 °C) and consumed 35% of the host's biomass. Infections were not typically lethal to F. panamensis, but sometimes forced the host from its lorica. Several D. aspida were found in the cytoplasm of many hosts, and the number of parasites infection-1 was directly related to infection level. Parasite prevalence averaged 24.0 and 11.5% with mean number of parasites infection-1 being 1.5 and 1.3 for Chesapeake Bay and Indian River samples, respectively. D. aspida was estimated to remove up to 68% of host standing stock d-1 with a mean of 10% for all samples. The average impact of parasitism on F. panamensis populations was somewhat less than would be expected from copepod grazing. 相似文献
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In this study a direct interaction of a metabolite of 3,4,3′,4′-tetrachlorobiphenyl with transthyretin (prealbumin) was observed, leading to reduced plasma levels of retinol, RBP and thyroxin in rats and mice. 相似文献
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Concentrations of dioxin-like PCB congeners in unweathered Aroclors by HRGC/HRMS using EPA Method 1668A 总被引:6,自引:0,他引:6
Rushneck DR Beliveau A Fowler B Hamilton C Hoover D Kaye K Berg M Smith T Telliard WA Roman H Ruder E Ryan L 《Chemosphere》2004,54(1):79-87
We have determined the congener compositions of nine commercial Aroclor products of polychlorinated biphenyls (PCBs) to the sub-part-per-million level using high-resolution gas chromatography combined with high-resolution mass spectrometry according to US Environmental Protection Agency (EPA) Method 1668A. These Aroclor composition data should allow improved characterization and risk assessment of PCB contamination at hazardous waste sites, particularly for dioxin-like PCB congeners. By combining the data on the concentrations of each dioxin-like congener with its World Health Organization toxicity equivalency factor, we have established dioxin toxic equivalent concentrations for each pure Aroclor product. 相似文献
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Åke Berg Bengt Ehnström Lena Gustafsson Tomas Hallingbäck Mats Jonsell Jan Weslien 《Conservation biology》1995,9(6):1629-1633
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The aim of this study was to analyse the occurrence of corncrakes in two Swedish meadow sites managed by mowing and grazing, but also with abandoned meadows. Most corncrakes (58%) on meadows were found in unmanaged areas without subsidies to the farmers (i.e. areas with tall vegetation). Several corncrakes (62%) were found in restored areas, managed for less than 10 of the last 40 years, fewer (38%) in areas under continuous management. Vegetation height was negatively associated with number of years of management the last 40 years, and the continuously managed areas were avoided by corncrakes. Sites where corncrake territories occur regularly should be managed to maintain tall vegetation suitable for the species, which requires increased use of mowing. However, the results from our study also suggest that yearly mowing might result in a vegetation structure that is avoided by corncrakes. To achieve a balance between tall grassy vegetation and prevention of succession to scrub a possible management regime would therefore be mowing at intervals of a few years. 相似文献
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Weight-specific contents of asorbic acid, thiamin, riboflavin, niacin, pantothenic acid, vitamin B6, biotin, folate and vitamin B12 were analysed in natural zooplankton collected from a sea water lagoon in a halibut fry production plant. The samples of
natural zooplankton were collected from April/May to the end of June during two consecutive spring blooms. For comparison,
the same vitamins were measured in nauplii of Artemia franciscana, just after hatching and after enrichment for 24 and 48 h with a commercial diet. The changes in vitamin content in zooplankton,
which consisted mainly of Temora longicornis, during the two spring blooms were <2.5-fold for each specific vitamin. The large number of high quality halibut fry produced
using the plankton as a dietary source suggests that the plankton contained sufficient amounts of all water-soluble vitamins.
With the exception of thiamin and ascorbic acid, Artemia– both newly hatched and enriched for 24 and 48 h – contained higher levels of water-soluble vitamins than natural zooplankton.
Enrichment feeding of Artemia for 48 h stabilised or increased the level of the water-soluble vitamins.
Received: 8 March 1999 / Accepted: 21 February 2000 相似文献
40.