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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of estimates of the predatory impact of ctenophores by two independent techniques (1982)
    Springer
    Marine biology 68 (1982), S. 61-65 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The common methods for estimating food consumption in the environment involve either (1) performing experiments in the laboratory and relating food concentrations used to those in the environment, or (2) analyzing gut contents of animals directly from the environment and estimating food consumption by some knowledge of gut residence time. Both techniques involved compromises and assumptions. The greater precision and speed of the laboratory approach is counterbalanced by the impossibility of duplicating the natural feeding milieu. We compared predation rates of the ctenophores from gut content analysis of ctenophores in 1 300 m3 enclosures, with the estimates of expected predatory effects based on controlled laboratory experiments, over a wide range of ctenophore size and food concentration. Despite some larger discrepancies, the two methods often yielded results within a factor of two of each other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393141
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of copper and cadmium on growth, swimming and predator avoidance in Eurytemora affinis (Copepoda) (1983)
    Springer
    Marine biology 77 (1983), S. 299-306 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this study we demonstrate the sensitivity of swimming behavior and predator-escape responses of nauplii of the estuarine copepod Eurytemora affinis to sublethal doses of Cu and Cd. Behavior was generally altered at metal doses below those affecting growth rates or survival of the copepods. Swimming velocities of Cu-dosed nauplii were different from controls at all concentrations of Cu tested (10–50 μg l-1 total Cu) after 24- to 48-h exposure, whereas development rate of nauplii was significantly reduced only after 96 h at 25 μg l-1. The 96 h LC50 for Cu was approximately 30 μg l-1 Cu. Naupliar swimming velocity was also affected by Cd. Swimming speeds were reduced after 24 h at 130 μg l-1, and development was slowed after 48 h at 116 μg Cd l-1. The 96-h LC50 was 〉120 μg l-1. Little is known of the adaptive role of specific motile behaviors in the success of larval copepods. We investigated the relationship of swimming speed to predator — prey interactions of the nauplii using both real and simulated predators. Nauplii exposed to Cu for 24 h were observed to be generally hyperactive, a condition which could increase their encounter frequency with predators. Reduced numbers of escape responses of nauplii to a simulated predator, another indication of increased vulnerability to predation, were observed only after 48-h exposure to Cu. Nevertheless, feeding rates of non-dosed larval striped bass on dosed nauplii (24 h at 25 μg Cu l-1) were significantly higher than on control nauplii. Feeding rates of larval mysid shrimp, however, were not higher on similarly dosed nauplii; 24 h exposure of nauplii to 〉30 μg Cu l-1 did result in increased predation by mysids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395819
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A scanning electron microscope study of the mandibular morphology of boreal copepods (1975)
    Springer
    Marine biology 30 (1975), S. 175-182 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Morphological details of the mandibular blades of 11 species of copepods were examined with scanning electron microscopy. The micrographs improved our understanding of the complex toothed edge of the mandibular blade, which in turn aids in identification of the copepod prey of chaetognaths by gut-content analysis. Beklemishev's discovery of siliceous tooth crowns in calanoid copepods was confirmed for most of the species examined. Long, sharp projections on the crowns of herbivorous species, and the deep grooves into which they fit on the teeth of the opposite mandible, suggest a cracking rather than a grinding function for these teeth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391591
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanics of prey selection by ephyrae of the scyphomedusa Aurelia aurita (1997)
    Springer
    Marine biology 130 (1997), S. 213-222 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In situ feeding patterns of ephyrae of the jellyfish Aurelia aurita (Linnaeus) revealed the importance of relatively large (〉1 mm) prey in the diet of these scyphozoan predators. These studies were carried out in Narragansett Bay, Rhode Island, USA in March and April, from 1993 through 1996. Rotifers were the only small prey ingested in quantity, and then only when they were unusually abundant in the plankton. Copepod nauplii, similar in size to rotifers and equally abundant, were rarely consumed. Since copepods evince rapid escape responses, this observation suggested a role for prey escape in determining prey vulnerability, while the predominance of large prey in the diet suggested a role for prey size. Using two dimensional video observations of free-swimming ephyrae and their prey in the laboratory we tested hypotheses about the mechanisms underlying these dietary patterns, comparing mechanisms for capture of large versus small prey and for prey of equal size but differing escape behaviors. Capture efficiencies of ephyrae feeding on large prey were 4 to 12 times greater than for small prey taxa. Capture efficiencies for prey of equal size also differed significantly, indicating that other factors influence the outcome of predator–prey interactions. Most prey captures occurred while the ephyrae were swimming and creating fluid flows that entrained prey into the subumbrellar region. Even copepod nauplii were frequently drawn into the subumbrella of swimming ephyrae despite average potential escape velocities (25.7 mm s−1) that exceeded mean maximum velocity of fluid flows around the ephyrae (13.1 mm s−1). Large prey were more likely than small prey to contact nematocyst-bearing surfaces both before and after entrainment in flow fields. With regard to behavior, prey escape speeds were not the only predictor of prey vulnerability. Prey that continued swimming after entrainment (rotifers and brine shrimp) were captured more often than prey of equal size that ceased normal swimming (copepod nauplii and barnacle nauplii). Copepod nauplii were the prey least likely to be captured because they either “played dead” and were expelled from the subumbrella of the ephyrae before contacting a surface, or they eventually escaped at high velocity. These observations indicate that size-selective predation by ephyrae of A. aurita can be influenced by a variety of behavioral responses of the prey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050241
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  • 5
    Electronic Resource
    Electronic Resource
    Prey selection by the scyphomedusan predator Aurelia aurita (1994)
    Springer
    Marine biology 121 (1994), S. 335-341 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We describe feeding behavior of Aurelia aurita (Linnaeus) using gut content analyses of field-collected specimens and a mesocosm experiment. The field studies were conducted in Narragansett Bay, Rhode Island, USA from March to April 1988, and the mesocosm studies were done at the Marine Ecosystems Research Laboratory at the University of Rhode Island. Patterns of prey selection changed with medusa diameter. Smaller medusae (12 mm diameter) consumed mostly hydromedusan prey whereas larger medusae (up to 30 mm diameter) ingested greater numbers of copepod prey. While larger medusae did feed on copepods, their diet also contained more barnacle nauplii and hydromedusae than expected from the relative abundances of these prey types in plankton samples. A marginal flow mechanism of feeding by A. aurita provided an explanation for the patterns of prey selection we observed in medusae of different sizes and among widely divergent prey types. Our data indicated that large prey, with escape speeds slower than the marginal flow velocities around the bell margins of A. aurita, made up a substantial fraction of the daily ration when they were available. Such prey species may be more important to nutrition than the more abundant copepods and microzooplankton. Successful development of young medusae may depend upon an adequate supply of slowly escaping prey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346742
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  • 6
    Electronic Resource
    Electronic Resource
    Vulnerability of the copepod Acartia tonsa to predation by the scyphomedusa Chrysaora quinquecirrha : effect of prey size and behavior (1998)
    Springer
    Marine biology 132 (1998), S. 237-245 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although scyphomedusae have received increased attention in recent years as important predators in coastal and estuarine environments, the factors affecting zooplankton prey vulnerability to these jellyfish remain poorly understood. Current models predicting feeding patterns of cruising entangling predators, such as Chrysaora quinquecirrha (Desor, 1948), fail to account for the selection of fast-escaping prey such as copepods. Nevertheless, our analysis of gastric contents of field-collected medusae showed that this scyphomedusa fed selectively on the calanoid copepod Acartia tonsa (Dana, 1846) and preferentially ingested adult over copepodite stages. We measured feeding rates in a planktonkreisel while simultaneously videotaping predator–prey interactions. C. quinquecirrha consumed adult A. tonsa ten times faster than copepodites. Differences in prey behavior, in the form of predator–prey encounter rates or post-encounter escape responses, could not account for the elevated feeding rates on adults. Prey size, however, had a dramatic impact on the vulnerability of copepods. In experiments using heat-killed prey, feeding rates on adults (1.5 times longer than copepodites) were 11 times higher than on copepodites. In comparison, medusae ingested heat-killed prey at only two to three times the rate of live prey. These results suggest that during scyphomedusan–copepod interactions, prey escape ability is important, but ultimately small size is a more effective refuge from predation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050389
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  • 7
    Electronic Resource
    Electronic Resource
    The use of life-tables for evaluating the chronic toxicity of pollutants toMysidopsis bahia (1982)
    Springer
    Hydrobiologia 93 (1982), S. 179-187 
    Details
    ISSN: 1573-5117
    Keywords: Mysidacea ; life-tables ; populations ; toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examines the application of population statistics to laboratory-derived toxicological data for the purpose of developing a predictive model that assesses the population consequences of pollutant and environmentally-induced stress. Life tables are used to calculate age-specific survivorship, fecundity, intrinsic rate of population increase (r), and reproductive value (Va), for populations ofMysidopsis bahia chronically exposed, in separate tests, to mercury and nickel. The population statistics, r, and Va, and pollutant dose are defined quantitatively, and the critical value (r = 0) for the intrinsic rate of population increase is compared with traditional toxicological measures of acute and chronic toxicity. The effects of an environmental variable, predation, significantly reduce the critical value (r = 0) for the intrinsic rate of growth and demonstrate the interactions of multiple stressors. The use of the population statistic, r, is recommended for estimating the ecological significance of toxicological data and for facilitating the assessment of interactions between pollutant-stressed populations and dynamic environmental pressures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008111
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    Paper (German National Licenses)
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