| 1. |
- Grebner, Wiebke, 1985, et al.
(författare)
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Induction of defensive traits in marine plankton—new copepodamide structures
- 2019
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 64:2, s. 820-831
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Tidskriftsartikel (refereegranskat)abstract
- Marine zooplankton release chemical cues, which trigger defenses in unicellular phytoplankton, such as increased toxin production and changes of colony sizes. Here, we identify the structure of two novel alarm cues belonging to the group of copepodamides. Similar to the known copepodamides, one of the compounds described is shown to trigger both amnesic and paralytic shellfish toxin production and chain length shortening in Skeletonema marinoi. In addition, we report the putative structures of another 21 copepodamides, which constitute 28% of the total copepodamides extractable from whole animals, suggesting that the copepodamide concentrations have been underestimated in earlier studies. We introduce a structure‐based nomenclature to handle the increasing number of copepodamides. Analysis of 12 copepod species showed that marine calanoid and freshwater cyclopoid copepods contain copepodamides. The only harpacticoid included in the analysis, Tigriopus californicus, did not appear to produce detectable amounts of copepodamides. Feeding experiments revealed that copepodamide compositions depend on both diet and species‐specific properties. Copepodamides induce both morphological and biochemical defensive traits in phytoplankton and may drive large‐scale trait–mediated effects in marine food webs. The more comprehensive list of copepodamides reported here makes it possible to explore the role of the copepodamide signaling system in the pelagic ecosystem in greater detail.
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| 2. |
- 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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| 3. |
- Trapp, Aubrey, et al.
(författare)
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Eavesdropping on plankton-can zooplankton monitoring improve forecasting of biotoxins from harmful algae blooms?
- 2021
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 66:9, s. 3455-3471
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Tidskriftsartikel (refereegranskat)abstract
- Harmful algae bloom (HAB) forecasting has developed rapidly over recent decades, but predicting harmful levels of marine biotoxins in shellfish is still a challenge. New discoveries suggest that predator-prey interactions may be an important driver in the formation of HABs. Key species of harmful algae respond to copepod infochemicals with increased toxin production. In addition, copepods feed selectively on less defended prey, which may further promote harmful taxa. Here we explore if eavesdropping on predator-prey dynamics by monitoring zooplankton can improve HAB forecasting. We first examine an 8-yr time series including copepod biomass, harmful algae cells (Dinophysis spp.), and diarrhetic shellfish toxins in blue mussels (Mytilus edulis) using generalized additive models. Models including copepod biomass more accurately predicted okadaic acid in mussels than phytoplankton alone. We then apply this connection more narrowly by analyzing the specific copepod exudates known to induce toxin production, copepodamides, from the mussels sampled in biotoxin monitoring. Adding copepodamide data from shellfish extracts increased model performance compared to copepod biomass. Results suggest that including grazing effects through copepodamide measurements may provide a cost-efficient way to improve accuracy and lead time for predicting the accumulation of microalgal toxins in shellfish.
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| 4. |
- 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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| 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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