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  • 1
    Electronic Resource
    Electronic Resource
    Capillary gas chromatography with ultraviolet spectrometric detection (1980)
    s.l. : American Chemical Society
    Analytical chemistry 52 (1980), S. 736-740 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac50054a032
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  • 2
    Electronic Resource
    Electronic Resource
    Ammonium excretion by gelationous zooplankton and their contribution to the ammonium requirements of microplankton in Chesapeake Bay (1993)
    Springer
    Marine biology 116 (1993), S. 451-458 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ammonium excretion rates of recently collected specimens of gelatinous zooplankton, the scyphomedusan Chrysaora quinquecirrha DeSor and the etenophore Mnemiopsis leidyi A. Agassiz, were correlated with body mass and water temperature in measurements made from April to October 1989 and 1990. Rates ranged between 3.5 and 5.0 μg atoms NH 4 + -N (g dry wt)-1h-1 for C. quinquecirrha and 3.0 to 4.9 μg atoms NH 4 + -N (g dry wt)-1h-1 for M. leidyi. Excretion rate equations and in situ data on the size distributions and biomasses of gelatinous zooplankters and water temperature were used to estimate the contribution of ammonium by medusae and ctenophores to mesohaline Chesapeake Bay waters on several dates during April to October 1989 and 1990. We then compared the estimated contributions to direct measurements of 15NH 4 + uptake by microplankton. The maximum estimated regeneration by gelatinous zooplankton was 5.8 μg atoms NH 4 + -N m-3h-1 at night in August 1990, when medusae biomass was greatest. This represents about 4% of the ammonium required by the microplankton. During the daytime on all dates, less than 1% of the ammonium required by microplanktion was supplied by gelatinous zooplankton. Therefore, gelatinous zooplankton appear to play a minor role in the ammonium cycle of Chesapeake Bay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350062
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  • 3
    Electronic Resource
    Electronic Resource
    Escape of the ctenophore Mnemiopsis leidyi from the scyphomedusa predator Chrysaora quinquecirrha (1997)
    Springer
    Marine biology 128 (1997), S. 441-446 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ctenophore Mnemiopsis leidyi A. Agassiz, 1865 is known to be eaten by the scyphomedusan Chrysaora quinquecirrha (Desor, 1948), which can control populations of ctenophores in the tributaries of Chesapeake Bay. In the summer of 1995, we videotaped interactions in large aquaria in order to determine whether M. leidyi was always captured after contact with medusae. Surprisingly, M. leidyi escaped in 97.2% of 143 contacts. The ctenophores increased swimming speed by an average of 300% immediately after contact with tentacles and 600% by mid-escape. When caught in the tentacles of C. quinquecirrha, the ctenophores frequently lost a portion of their body, which allowed them to escape. Lost parts regenerated within a few days. The striking ability of M. leidyi to escape from C. quinquecirrha may be critically important in maintaining ctenophore populations in situ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050110
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  • 4
    Electronic Resource
    Electronic Resource
    Swimming and feeding by the scyphomedusa Chrysaora quinquecirrha (1997)
    Springer
    Marine biology 129 (1997), S. 355-362 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The semaeostome scyphomedusa, Chrysaora quinquecirrha (Desor, 1848), is an abundant and important planktonic predator in estuaries and coastal waters of the eastern USA during the summer. We videotaped free-swimming medusae in the laboratory and in the field in order to determine the relationship between swimming motions and prey encounter with capture surfaces. Medusae were collected from the Choptank River (Chesapeake Bay) in September 1992 and in the Niantic River, Connecticut, USA in July 1994. We used newly hatched Artemia sp. nauplii and fluorescein dye to trace water motions around swimming medusae. Swimming results in a pulsed series of toroids which travel along the medusan oral arms and tentacles. Prey are entrained in this flow and the location of naupliar encounter was influenced by the phase of the pulsation cycle during which entrainment occurred. Flow-field velocities, measured by tracking particles adjacent to the bell margin during contraction, increased with bell diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050175
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  • 5
    Electronic Resource
    Electronic Resource
    Selective predation and caloric consumption by the siphonophore Rosacea cymbiformis in nature (1981)
    Springer
    Marine biology 63 (1981), S. 283-294 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Individuals of the siphonophore Rosacea cymbiformis (Chiaje, 1822) were collected in surface waters of the Gulf of California during July/August 1978, off Southern California during May 1980, and in the Sargasso Sea during July 1979. Specimens were preserved within 30 min after capture, and the ingested prey in the gastrozooids were examined microscopically and identified to the closest practical taxon. Most gastrozooids (50 to 84%) contained recognizable prey organisms. The prey were primarily copepods, but crab zoeae, pelagic molluscs, juvenile shrimps and mysids were also commonly eaten. There were significant differences between the sizes and types of prey organisms that had been ingested and that were available in the environment of the siphonophores. Electivity indices for the prey demonstrated that the large and/or active prey were selected. The feeding selectivity exhibited by the siphonophores probably depends upon speed and diameter of the prey, which affect the frequency of contact with the siphonopore tentacles. Behavioral observations suggest that R. cymbiformis feeds primarily in the light. Digestion experiments indicate that most prey remain in the gastrozooids for 8 h or more before egestion. The caloric values of common prey types were derived from their length to dry weight regressions. The caloric consumption of R. cymbiformis during the 4 to 6 h feeding period following sunrise was estimated to be from 0.109 to 0.365 cal per gastrozooid; the daily caloric consumption was projected to be at least 2.4 to 8.2 times that required to balance metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395998
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  • 6
    Electronic Resource
    Electronic Resource
    Digestion rates and assimilation efficiencies of siphonophores fed zooplankton prey (1983)
    Springer
    Marine biology 73 (1983), S. 257-261 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Digestion times and assimilation efficiencies are critical factors used in calculations of carbon and nitrogen budgets. Digestion times of natural copepod prey differed significantly among 4 genera of siphonophores (P〉0.001), from a minimum of 1.6 h to a maximum of 9.6 h. Assimilation efficiencies, in contrast, were uniformly high; 87 to 94% for carbon and 90 to 96% for nitrogen. Nitrogen assimilation was consistently greater than carbon assimilation. Assimilation efficiencies calculated according to dry weight substantially underestimated assimilation of carbon and nitrogen, while calculations using ash-free dry weights and ash-free to dry weight ratios approached values for carbon assimilation. These values are appreciably higher than most of the assimilation efficiencies previously measured for a few other planktonic carnivores. These results indicate very efficient digestion of food by siphonophores in oceanic environments where prey densities are low.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392251
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  • 7
    Electronic Resource
    Electronic Resource
    Prey, feeding rates, and asexual reproduction rates of the introduced oligohaline hydrozoan Moerisia lyonsi (1999)
    Springer
    Marine biology 134 (1999), S. 317-325 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Moerisia lyonsi Boulenger (Hydrozoa) medusae and benthic polyps were found at 0 to 5‰ salinity in the Choptank River subestuary of Chesapeake Bay, USA. This species was introduced to the bay at least 30 years before 1996. Medusae and polyps of M. lyonsi are very small and inconspicuous, and may occur widely, but unnoticed, in oligohaline waters of the Chesapeake Bay system and in other estuaries. Medusae consumed copepod nauplii and adults, but not barnacle nauplii, polychaete and ctenophore larvae or tintinnids, in laboratory experiments. Predation rates on copepods by medusae increased with increasing medusa diameter and prey densities. Feeding rates on copepod nauplii were higher than on adults and showed no saturation over the range of prey densities tested (1 to 64 prey l−1). By contrast, predation on copepod adults was maximum (1 copepod medusa−1 h−1) at 32 and 64 copepods l−1. Unexpectedly, M. lyonsi colonized mesocosms at the Horn Point Laboratory during the spring and summer in 4 years (1994 to 1997), and reached extremely high densities (up to 13.6 medusae l−1). Densities of copepod adults and nauplii were low when medusa densities were high, and estimated predation effects suggested that M. lyonsi predation limited copepod populations in the mesocosms. Polyps of M. lyonsi asexually produced both polyp buds and medusae. Rates of asexual reproduction increased with increasing prey availability, from an average total during a 38 d experiment of 9.5 buds polyp−1 when each polyp was fed 1 copepod d−1, to an average total of 146.7 buds polyp−1 when fed 8 copepods d−1. The maximum daily production measured was 8 polyp buds and 22 medusae polyp−1. The colonizing potential of this hydrozoan is great, given the high rates of asexual reproduction, fairly wide salinity tolerance, and existence of a cyst stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050549
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  • 8
    Electronic Resource
    Electronic Resource
    Dietary composition and diel feeding patterns of epipelagic siphonophores (1981)
    Springer
    Marine biology 65 (1981), S. 83-90 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Prey consumption patterns are described for 24 species of epipelagic siphonophores studied during 1977–1980 in the Gulf of California, off Southern California, in the Sargasso Sea, and in Friday Harbor, Washington. Of the species, 7 were studied by day and at night, 15 were studied only by day, and 2 were studied only at night. Each of the 3 suborders of siphonophores had a characteristic diet. Siphonophores in the suborder Cystonectae, which had large gastrozooids, fed primarily on fish larvae. Species in the suborder Physonectae, which generally had few, large gastrozooids, consumed some small copepods, but consumed mainly large copepods and a variety of large, noncopepod prey. Species in the suborder Calycophorae, which generally had many small gastrozooids, fed mainly on small copepods, and also on other small prey organisms. The maximum size of prey tended to be correlated with gastrozooid length for all the siphonophores studied. For a given siphonophore species, the number of ingested prey was greatest at localities where prey organisms were most abundant in the surrounding seawater. For siphonophore species collected both day and night, there was a tendency for more prey to be consumed at night. Behavioral observations in the laboratory indicated that of 7 siphonophore species tested, 2 fed only in the light, and another fed only in the dark.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397071
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  • 9
    Electronic Resource
    Electronic Resource
    Vulnerability of larval herring (Clupea harengus pallasi) to capture by the jellyfish Aequorea victoria (1987)
    Springer
    Marine biology 94 (1987), S. 157-162 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gut-content analysis of Aequorea victoria collected in Kulleet Bay, Vancouver Island, British Columbia, Canada, in 1983, showed that the jellyfish consumed herring (Clupea harengus pallasi) larvae, primarily yolksac [≦8mm notochord length (NL)] and post-yolksac larvae (≦12mm NL). Behavioral experiments with laboratory-reared larvae showed that the ability to escape after contact with a jellyfish tentacle increased dramatically from yolksac through pre-metamorphic larvae (up to 20 mm NL). Early yolksac larvae were captured in 91% of the contacts with a tentacle, but the largest larvae in only 13%. Unfed larvae were more vulnerable to jellyfish predation than fed larvae of the same age. Our results indicate that A. victoria is most important as a predator of herring larvae during a short period after the larvae hatch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392927
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  • 10
    Electronic Resource
    Electronic Resource
    Separation of Permanent Gases by Open Tubular Adsorption Columns (1964)
    [s.l.] : Nature Publishing Group
    Nature 201 (1964), S. 1321-1322 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Petitjean and Leftault1, and Mohnke and Saffert2, described open tubular adsorption columns prepared by activating the inner walls of capillary tubing. More recently, Halasz and Horvath3, Schwartz, Brasseaux and Shoemake4, and Kirkland5 discussed the preparation of open tubular adsorption columns ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2011321b0
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