| 1. |
- Pavia, Henrik, 1964, et al.
(författare)
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Chemical defences against herbivores
- 2012
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Ingår i: Chemical ecology in aquatic systems. - New York, US : Oxford University Press. - 9780199583096 ; , s. 210-235
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Bokkapitel (refereegranskat)abstract
- In recent years it has become increasingly clear that chemical interactions play a fundamental role in aquatic habitats and have far-reaching evolutionary and ecological consequences. A plethora of studies have shown that aquatic organisms from most taxa and functional groups respond to minute concentrations of chemical substances released by other organisms. However, our knowledge of this 'chemical network' is still negligible. Chemical interactions can be divided into two larger sub-areas based on the function of the chemical substance. First, there are interactions where chemical substances are toxic to other organisms and are used as a defense against consumers (including both herbivores and predators) or a weapon against competitors (allelopathy). Second, chemical substances mey be used as a source for information of the environment; for example: how can I find the optimal habitat, the best food, the nicest partner, and avoid being eaten? Aquatic organisms are able to detect and respond to extremely low concentrations of chemical cues to answer all these questions. The book aims at connecting these intriguing chemical interactions with traditional knowledge of organism interactions. Chemical ecology in aquatic systems covers a wide range of studies, both plant and animal, from different geographic regions and habitats-pelagic as well as benthic. Most of the chemical interactions are similar in freshwater and marine habitats and this book therefor strives at integrating work on both systems. This accessible, research-level text is aimed at graduate students and professional researchers in the fields of limnology, marine ecology, evolutionary biology, behavioral ecology, and chemical ecology.
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| 2. |
- Bergkvist, Johanna, 1980, et al.
(författare)
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Grazer-induced chain length plasticity reduces grazing risk in a marine diatom
- 2012
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590. ; 57:1, s. 318-324
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Tidskriftsartikel (refereegranskat)abstract
- We show that Skeletonema marinoi suppresses chain formation in response to copepod cues. The presence of three different copepod species (Acartia tonsa, Centropages hamatus, or Temora longicornis) significantly reduced chain length. Furthermore, chain length was significantly reduced when S. marinoi was exposed to chemical cues from caged A. tonsa without physical contact with the responding cells. The reductions in chain length significantly reduced copepod grazing; grazing rates on chains (four cells or more) were several times higher compared to that of single cells. This suggests that chain length plasticity is a means for S. marinoi to reduce copepod grazing. In contrast, chain length was not suppressed in cultures exposed to the microzooplankton grazer Gyrodinium dominans. Size-selective predation may have played a key role in the evolution of chain formation and chain length plasticity in diatoms.
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| 3. |
- Heuschele, J., et al.
(författare)
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The chemical ecology of copepods
- 2014
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 36:4, s. 895-913
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Forskningsöversikt (refereegranskat)abstract
- An increasing number of studies show the importance of chemical interactions in the aquatic environment. Our understanding of the role of chemical cues and signals in larger crustaceans has advanced in the last decades. However, for copepods, the most abundant metazoan zooplankton and essential for the functioning of the marine food web, much is still unknown. We synthesize current knowledge about chemical ecology of copepods including foraging, survival and reproduction. We also compile information on the sensory apparatus and new analytical approaches that may facilitate the identification of signal molecules. The review illustrates the importance of chemical interactions in many aspects of copepod ecology and identifies gaps in our knowledge, such as the lack of identified infochemicals and electrophysiological studies to confirm the function of sensory structures. We suggest approaches that are likely to further our understanding of the role of chemical interactions in the pelagic ecosystem.
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| 4. |
- Kiorboe, Thomas, et al.
(författare)
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Havets dufte
- 2013
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Ingår i: Aktuel naturvidenskab. - 1399-2309 .- 1602-3544. ; :3, s. 30-33
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Lombard, F., et al.
(författare)
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Active prey rejection in the filter-feeding appendicularian Oikopleura dioica
- 2011
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590. ; 56:4, s. 1504-1512
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Tidskriftsartikel (refereegranskat)abstract
- We describe different modes of prey rejection in a filter-feeding appendicularian, Oikopleura dioica. Nonselective prey rejection occurs by intermittent rejection through reversal of the feeding current of all particles when the pharyngeal filter is overloaded, AND by accidental loss through the spiracles of all particles that have entered the house when the pharyngeal filter occasionally breaks. In addition, selective prey rejection of individual particles may occur in the mouth by reversal of the ciliary current in the spiracle: the unwanted particle is expelled with a small amount of water. Up to four rejections of individual particles may occur per second. This active rejection is based on both the size and the chemical characteristics of the individual particle. A significantly higher rejection rate was found for toxic dinoflagelate (68%) compared to similar sized nontoxic ones (34%); exponentially growing algae were less rejected than senescent ones; and nutrient-depleted algae were more rejected than nutrient-replete cells. For nontoxic particles, prey size relative to the size of the appendicularian was the main prey selection criterion and the optimal prey size (> 80% acceptance) for O. dioica is between 0.4% and 2% of their own size, whereas the minimum and maximum particle sizes that they can ingest range from 0.04% to 20% of their own size. This prey size spectrum is much broader than that found in most other planktivorous organisms and demonstrates that appendicularians are simultaneous microphageous and macrophageous planktonic grazers. © 2011, by the American Society of Limnology and Oceanography, Inc.
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| 6. |
- Selander, Erik, 1973, et al.
(författare)
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Fight and flight in dinoflagellates? Kinetics of simultaneous grazer-induced responses in Alexandrium tamarense
- 2012
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 57:1, s. 58-64
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Tidskriftsartikel (refereegranskat)abstract
- We monitored the kinetics of grazer-induced responses in the marine dinoflagellate Alexandrium tamarense. Chemical cues from each of three calanoid copepods (Calanus sp., Centropages typicus, and Acartia tonsa) induced increased toxicity and suppressed chain formation in A. tamarense. Both chemical and morphological responses augmented over 3 d. Toxicity subsequently averaged 299% higher than controls, and average biovolume 24% lower than controls because of suppression of chain formation in grazed treatments. Grazer-induced toxicity returned to control levels after approximately 11 d, equivalent to five cell divisions, and average biovolume returned to control levels within 1 to 4 d (one to two cell divisions). This suggests that dinoflagellates simultaneously reduce grazer encounter rates and increase chemical defense levels in the presence of copepod grazers. Media replacement experiments showed that the inducing cue(s) attenuate rapidly in seawater, which allows A. tamarense to adjust resource allocation to grazer-induced responses to follow fluctuations in grazer density. Grazer-induced responses, however, develop too slowly to be accounted for in short-term grazing experiments with laboratory cultures.
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| 7. |
- Selander, Erik, 1973, et al.
(författare)
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Grazer cues induce stealth behavior in marine dinoflagellates
- 2011
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 108:10, s. 4030-4034
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Tidskriftsartikel (refereegranskat)abstract
- Chain formation is common among phytoplankton organisms but the underlying reasons and consequences are poorly understood. Here we show that chain formation is strongly impaired by waterborne cues from copepod grazers in the dinoflagellate Alexandrium tamarense. Chains of Alexandrium cells exposed to copepod cues responded by splitting into single cells or shorter chains. Motion analysis revealed significantly lower swimming velocities for single cells compared with chains, with two- to fivefold higher simulated predator encounter rates for two- and four-cell chains, respectively. In addition, the few remaining two-cell chains in grazed treatments were swimming at approximately half the speed of two-cell chains in treatments without grazers, which reduced encounter rates with grazers to values similar to that of single cells. Chain length plasticity and swimming behavior constitute unique mechanisms to reduce encounters with grazers. We argue that dinoflagellates can regulate the balance between motility and predator avoidance by adjusting chain length. The high predator encounter rate for motile chains may have contributed to the low prevalence of chain formation in motile phytoplankton compared with in nonmotile phytoplankton where chain formation is more common.
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| 8. |
- Selander, Erik, 1973, et al.
(författare)
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Parasitic anemone infects the invasive ctenophore Mnemiopsis leidyi in the North East Atlantic
- 2010
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Ingår i: Biological invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 12:5, s. 1003-1009
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Tidskriftsartikel (refereegranskat)abstract
- We report of the first finding of parasitic sea anemone larvae infecting the invasive ctenophore Mnemiopsis leidyi in the North East Atlantic. Parasitic anemone larvae are common in the native habitat of Mnemiopsis, but have not previously been reported from any of the locations where Mnemiopsis has been introduced. General morphology and 18S rRNA sequences support the identification of the larvae as Edwardsiella sp. Excised anemone larvae were reared through metamorphosis and confirmed the identification of the parasite. Both Mnemiopsis and Edwardsiella larvae were monitored weekly during 2007 and 2008 and parasitic larvae were recorded from September to November both years. The highest density was observed in September 2008 when Edwardsiidae larvae reached 2.3 ind m(-3). In 2008 total density of the parasite occasionally exceeded 40% of the host density and the potential consequences for Mnemiopsis population dynamics are discussed.
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| 9. |
- Sjoqvist, C., et al.
(författare)
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Effects of Grazer Presence on Genetic Structure of a Phenotypically Diverse Diatom Population
- 2014
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 67:1, s. 83-95
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Tidskriftsartikel (refereegranskat)abstract
- Studies of predator-prey systems in both aquatic and terrestrial environments have shown that grazers structure the intraspecific diversity of prey species, given that the prey populations are phenotypically variable. Populations of phytoplankton have traditionally considered comprising only low intraspecific variation, hence selective grazing as a potentially structuring factor of both genetic and phenotypic diversity has not been comprehensively studied. In this study, we compared strain specific growth rates, production of polyunsaturated aldehydes, and chain length of the marine diatom Skeletonema marinoi in both grazer and non-grazer conditions by conducting monoclonal experiments. Additionally, a mesocosm experiment was performed with multiclonal experimental S. marinoi populations exposed to grazers at different levels of copepod concentration to test effects of grazer presence on diatom diversity in close to natural conditions. Our results show that distinct genotypes of a geographically restricted population exhibit variable phenotypic traits relevant to grazing interactions such as chain length and growth rates. Grazer presence affected clonal richness and evenness of multiclonal Skeletonema populations in the mesocosms, likely in conjunction with intrinsic interactions among the diatom strains. Only the production of polyunsaturated aldehydes was not affected by grazer presence. Our findings suggest that grazing can be an important factor structuring diatom population diversity in the sea and emphasize the importance of considering clonal differences when characterizing species and their role in nature.
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| 10. |
- Smith, B.C., et al.
(författare)
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Toxin profile change in vegetative cells and pellicle cysts of Alexandrium fundyense after gut passage in the eastern oyster Crassostrea virginica
- 2011
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Ingår i: Aquatic biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 13:2, s. 193-201
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Vegetative cells and pellicle cysts of the toxic dinoflagellate Alexandrium fundyense Balech were fed to the eastern oyster Crassostrea virginica Gmelin under controlled conditions. Para lytic shellfish toxins (PSTs) were measured in vegetative cells and pellicle cysts prior to feeding and directly after passage through the oyster alimentary canal and defecation as intact cells. Oysters fed with vegetative cells and those fed with pellicle cysts accumulated toxins. One experimental treatment tested for direct uptake of toxins from the water (oysters and A. fundyense cells were separated by a screen); PSTs were not accumulated from the water by the oysters. There were no significant changes in total, per-cell toxicity after passage through the oyster alimentary canal, suggesting limited transfer of toxins from intact cells to the oysters. However, there were statistically significant changes in the toxin composition of cells following gut passage. Vegetative cells and pellicle cysts from feces had increased amounts of saxitoxin (STX) and decreased amounts of gonyautoxin 4 (GTX4) per cell, compared to amounts prior to gut passage. Following gut passage, pellicle cysts showed better survival in the feces than vegetative cells, which is consistent with the view of pellicle-cyst formation as a successful survival strategy against adverse conditions.
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