Inducible morphological defenses of Daphnia similis against Triops cancriformis and Notonecta maculata

Sven Ritschar1, Christian Laforsch1, Max Rabus1
1 Department of Animal Ecology I, University of Bayreuth

O 4.3 in BayCEERversity: Across scales, compartments & communities

12.10.2017, 16:00-16:15, H36, NW III

The expression of inducible morphological defenses in cladocerans of the genus Daphnia is a well-known and extensively studied phenomenon. However, so far unrecognized inducible defenses and novel defense mechanisms are still reported on a regular basis. These new findings are especially made in species inhabiting temporary ponds. In the present study, we investigated whether the pond-dwelling species Daphnia similis responds to predators with the expression of inducible morphological defenses. Therefore, a clone of D. similis was exposed to kairomones of the tadpole shrimp Triops cancriformis and the backswimmer Notonecta maculata, which are dominant predators in temporary waters. Here we show, that D. similis expresses distinct inducible morphological defenses against both predators: Triops-induced individuals expressed a significantly longer tail-spine, while body width decreased in comparison to non-induced individuals. Additionally, they also expressed so called micro defenses, i.e. significantly longer spinules and a larger spinulae bearing area (SBA) on the dorsal ridge and a shorter SBA on the ventral carapace margins. The Notonecta-induced D. similis expressed a significantly longer tail-spine, longer spinules and a larger SBA on the dorsal ridge than non-induced individuals. Additionally, a morphometric analysis of the head shape revealed significant, predator-specific changes in this trait. Thereby, Triops-induced individuals expressed a relatively flattened head with a pronounced dorsal edge, while Notonecta-induced individuals developed a high and strongly rounded head shape. Therefore, this study reveals the so far undescribed inducible defenses of D. similis against two top predators in temporary waters. Furthermore, the predator-dependent change in head shape is concordance with the “concept of modality” which takes the qualitative aspect of natural selection caused by predators into account. 


Keywords: Daphnia, inducible defenses, shape analysis, predation

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