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Diel vertical migration (DVM) is a common behavior in zooplankton to avoid visual predation as well as potentially hazardous light wavelengths. In deep transparent lakes of Patagonia, the dark pigmented mixotrophic ciliate Stentor araucanus inhabits the upper layers of the epilimnion and is resistant to ultraviolet radiation (UVR). Here, we investigated if the ciliate pigment called stentorin increases oxidative stress in its predators. We studied the DVM behavior of Mesocyclops araucanus and the presence of stentorin in field‐collected copepods and evaluated in the laboratory the rate at which the copepod releases stentorin. S. araucanus has a C : P ratio ∼ 170 (atomic), which is one half of that of the bulk seston of the lake resulting in a very good food source in a system with very low food quality. Compared to an alternative prey without stentorin, when feeding on Stentor, the copepod suffered high oxidative stress (increased glutathione S‐transferase activity) and the reduced glutathion levels increased from dark to visible and ultraviolet radiation. However, we also determined that exposure to only visible light was sufficient to cause oxidative stress. In the field, we observed that M. araucanus displays a larger amplitude DVM than other crustaceans, while the ciliate Stentor remained in the upper levels of the epilimnion. The DVM protects the copepods from stentorin‐induced oxidative stress during daytime. Our findings are the first to show that a compound of a zooplankton prey item can influence the vertical behavior of predators in order to minimize the negative effect.

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When eating a prey is risky: Implications for predator diel vertical migration

Modenutti

Wolinski

Souza

et al. 2017

Limnology & Oceanography

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Beyond body mass: how prey traits improve predictions of functional response parameters

Kalinoski

DeLong

2015

Oecologia

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Understanding the factors that determine the strength of predator-prey interactions is essential to understanding community structure and stability. Variation in the strength of predator-prey interactions often can be attributed to predator mass and prey mass, or abiotic factors like temperature. However, even when accounting for these factors, there remains a considerable amount of unexplained variation that may be attributed to other traits. We compiled functional response data from the literature to investigate how predator mass, prey mass, prey type (taxonomic identity), temperature, and prey defenses (hard vs soft integument) contributed to the variation found in the predator-prey interactions between freshwater cyclopoid copepods and their prey. Surprisingly, our results indicate that prey identity (taxonomic group) and defenses (hard vs soft integument) are more important for generating variation in interaction strengths than body mass and temperature. This suggests that allometric functions can only take us so far when attempting to better understand variation in individual predator prey interactions, and that we must evaluate how other traits influence interaction strengths. Identifying additional factors such as prey defenses may enable us to better predict potential changes in the structure and function of planktonic and other food webs by better accounting for the variation in the interactions between generalists and their many prey types.

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Predatory interactions between a cyclopoid copepod and three sibling rotifer species

et al. 2002

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SUMMARY 1. Cyclopoid copepod predation on rotifers affects the dynamics and structure of zooplankton communities. We address the differential vulnerability of three sympatric rotifer sibling species belonging to the Brachionus plicatilis species complex. These co‐occur with their cyclopoid predator, Diacyclops bicuspidatus odessanus. 2. Using video recording and tracking, we analysed the steps in predation including attack distance, attack angle, and rotifer species swimming in the presence and absence of the predator. Our results show the greater vulnerability of B. rotundiformis (the smallest species) to D. b. odessanus predation, which is associated with a high percentage of attacks after contact. Brachionus plicatilis (the biggest species) is the less vulnerable prey, with low percentage of attacks after contact and captures after attacks. Branchionus ibericus, the intermediate sized species, had also intermediate vulnerability. 3. The differential vulnerability provides insight into the coexistence and seasonal succession of these competing rotifer species. Our results show that the competitive superiority of B. rotundiformis may be balanced by its greater vulnerability to copepod predation.

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Cited by 7 publications

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When eating a prey is risky: Implications for predator diel vertical migration

When eating a prey is risky: Implications for predator diel vertical migration

Beyond body mass: how prey traits improve predictions of functional response parameters

Predatory interactions between a cyclopoid copepod and three sibling rotifer species

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