Interclonal variation, effectiveness and long-term implications of Triops-induced morphological defences in Daphnia magna Strauss

Abstract

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.