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Waterkeyn A.,Charles University | Waterkeyn A.,Research Center for Mediterranean Wetlands Tour du Valat | Van Pottelbergh N.,Charles University | Vanoverbeke J.,Charles University | And 3 more authors.
Hydrobiologia | Year: 2012

Since cladocerans from the genus Daphnia are known to have evolved several inducible defenses (morphological and life history shifts) against the notostracan predator Triops, we investigated whether hatching was also altered in response to Triops. We tested whether dormant eggs of Daphnia magna are able to detect Triops cancriformis kairomones in the water as a signal of predation pressure and alter their hatching response accordingly to avoid predation. We predicted that, in the presence of Triops kairomones, hatching fractions might be reduced (postponing hatching to a next growing season) and/or that hatching might peak earlier (increasing chances to reproduce before Triops becomes predatory). We also tested whether this response depended on the origin of the population. Ephippia from three D. magna populations, originating from one permanent lake and two temporary pond systems, were exposed to Triops kairomone and control treatments. We observed significant population differences in hatching patterns, both in terms of the fraction of eggs that hatch as well as the timing of hatching, with evidence for within-season bet-hedging through delayed hatching in the populations inhabiting temporary habitats. However, no indication was found that the populations also adjust their hatching pattern to the presence of Triops kairomones. © 2012 Springer Science+Business Media B.V. Source


Waterkeyn A.,Charles University | Waterkeyn A.,Research Center for Mediterranean Wetlands Tour du Valat | Vanoverbeke J.,Charles University | Van Pottelbergh N.,Charles University | Brendonck L.,Charles University
Journal of Plankton Research | Year: 2011

Dormant egg banks provide a means for many species to survive adverse conditions. This study describes a short-term experiment evaluating predation by the notostracan Triops cancriformis on dormant eggs buried in sediment, i.e. Daphnia ephippia and Triops dormant eggs (cannibalism). Significant predation was recorded on both dormant stages, with no apparent selection. These results indicate that Triops could eradicate the dormant eggs in surface sediments and thereby impact the benthic-pelagic coupling in aquatic systems. © 2011 The Author. Source


Rabus M.,Ludwig Maximilians University of Munich | Waterkeyn A.,Charles University | Waterkeyn A.,Research Center for Mediterranean Wetlands Tour du Valat | Van Pottelbergh N.,Charles University | And 2 more authors.
Journal of Plankton Research | Year: 2012

In response to the predatory tadpole shrimp Triops cancriformis Bosc. (Notostraca), the cladoceran Daphina magna develops a "bulky" morphotype as an inducible morphological defence. The aim of this study is to provide further insight in the Triops-induced defences by revealing interclonal variation of the induced traits, the effectiveness of the defence and their effects on the preys population structure. In a clonal comparison experiment, we showed that clones of D. magna differed in their morphological response to T. cancriformis. By conducting predation trials with different combinations of Daphnia and Triops size classes, we could demonstrate that the morphological defences act as an effective protection throughout the entire life-span of D. magna. Finally, a long-term mesocosm study showed a significant, positive correlation between Triops density and the expression of the defensive traits. Thus, it confirmed that T. cancriformis is a strong agent in structuring D. magna populations through predation and induction of protective traits. Hence, this study provides further insight into this recently discovered predatorprey system, and might contribute to the knowledge of mechanisms of ecological interactions and evolutionary dynamics in aquatic communities. © 2011 The Author. Published by Oxford University Press. All rights reserved. Source


Waterkeyn A.,Catholic University of Leuven | Waterkeyn A.,Research Center for Mediterranean Wetlands Tour du Valat | Vanschoenwinkel B.,Catholic University of Leuven | Grillas P.,Research Center for Mediterranean Wetlands Tour du Valat | Brendonck L.,Catholic University of Leuven
Limnology and Oceanography | Year: 2010

In a large-scale outdoor mesocosm experiment we studied the effects of salinity on successional patterns, diversity, and relative abundances of Camargue (southern France) temporary pool crustaceans. Eighty mesocosms were inoculated with a mixed resting egg bank and exposed to four different salinity treatments (0.5, 1.0, 2.5, and 5.0 g L-1) for a period of 7 months. Salinity significantly altered crustacean communities hatching from the resting egg bank through a number of direct and indirect effects. Salinity had a significant negative effect on the establishment of large branchiopods and copepods. Both richness and density of cladocerans, especially chydorids, were positively related to salinity, possibly due to the absence of biotic interactions with large branchiopods at the highest salinity values. We hypothesize that the salinity-mediated presence of the large branchiopod keystone group can shift the whole wetland regime from a zooplankton-rich clear-water state to a zooplankton-poor turbid state. Crustacean succession was significantly altered by salinity, by slowing down development rates, population growth or maturation rates of some species. This suggests that in addition to salinity changes, any alteration of wetland hydroperiod (e.g., through aridification or inappropriate water management) could have a synergistic effect on community structure and diversity of invertebrate communities, including some keystone species. © 2010, by the American Society of Limnology and Oceanography, Inc. Source


Waterkeyn A.,Catholic University of Leuven | Waterkeyn A.,Research Center for Mediterranean Wetlands Tour du Valat | Vanschoenwinkel B.,Catholic University of Leuven | Vercampt H.,Catholic University of Leuven | And 2 more authors.
Limnology and Oceanography | Year: 2011

In a large-scale and long-term outdoor mesocosm (400-liter) experiment, we studied the interacting effects of salinity and disturbance (hydrological) regime on the active and dormant crustacean communities of Mediterranean temporary wetlands (Camargue, southern France). Sixty-four mesocosms, inoculated with a regional species pool (mixed dormant egg banks), were exposed to a full factorial treatment combination of four salinity levels and four disturbance regimes during three consecutive years. Both in the active and dormant community component, considerable shifts in community composition occurred because of direct and probably also second-order effects of the treatments. All large branchiopod species had low long-term salinity tolerances and showed species-specific preferences for disturbance regimes according to their life cycle strategy. The highest salinity (5) was not limiting for cladocerans and ostracods, which thrived in the absence of the competitively stronger, predatory, and bioturbating large branchiopods. Copepods were negatively associated with salinity and coped better with the imposed biotic pressure. Zooplankton diversity and density peaked in intermediatedisturbance regimes, probably because only specialized species survived the high-disturbance regimes, whereas at low-disturbance frequencies high densities of predatory Triops controlled zooplankton communities. Although crustacean dormant egg banks can temporarily buffer against unfavorable conditions, persisting bad conditions may lead to their exhaustion within 4 to 10 yr. Predicted aridification (leading to more intense disturbance regimes) may result in the loss of late successional species (chydorids and ostracods), whereas salinization may wipe out sensitive freshwater species such as large branchiopods. © 2011, by the American Society of Limnology and Oceanography, Inc. Source

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