Phenotypic plasticity in threeDaphniagenotypes in response to predator kairomone: evidence for an involvement of chitin deacetylases

Abstract

The genetic background of inducible morphological defences in Daphnia is still largely unknown. Dissolved infochemicals from the aquatic larvae of the phantom midge Chaoborus induce so-called 'neck-teeth' in the first three post-embryonic stages of Daphnia pulex. This defence has become a textbook example of inducible defences. In a target gene approach, by using three Daphnia genotypes which show a gradient of neck-teeth induction in response to equal amounts of kairomone, we report a high correlation of neck-teeth induction in Daphnia pulex and relative gene expression of two chitin deacetylases. Further, previous studies suggested genes from both the juvenoid and the insulin hormone signalling pathways as well as several morphogenetic genes downstream to be responsible for neck-teeth induction in D. pulex. However, these data were not supported by our study. None of the three D. pulex clones showed an upregulation of these previously proposed candidate genes as a response to predator kairomone, which is interpreted as the result of refined methods used for both RNA sampling and kairomone enrichment yielding unambiguous results compared with earlier studies. The assessment of a clonal gradient of Daphnia in the presence and absence of infochemicals provides a promising approach to identify further genes involved in the induction of morphological defences by correlating gene expression and morphology.

Bayesian updating during development predicts genotypic differences in plasticity

“…; Christjani et al. ). However, when animals are exposed to cues from predators, changes in antipredator behavior typically occur more rapidly than changes in morphological antipredator defenses (Van Buskirk ; Hossie and Murray ; Orizaola et al.…”

“…For instance, many organisms express antipredator traits at the beginning of independent life, for example, as hatchlings, neonates, and seedlings (Osborn and Jaffe 1998;Laforsch and Tollrian 2004;Bosak et al 2013;Garla et al 2015). The expression of such traits can vary across genotypes prior to any exposure to cues from predators, and genotypes can differ with respect to the plasticity of those traits in response to cues from predators (Fischer et al 2014b;Sjoqvist et al 2014;Otte et al 2015;Christjani et al 2016). However, when animals are exposed to cues from predators, changes in antipredator behavior typically occur more rapidly than changes in morphological antipredator defenses (Van Buskirk 2002;Hossie and Murray 2012;Orizaola et al 2012).…”

Knowing the Enemy: Inducible Defences in Freshwater Zooplankton

“…Secondly, the expression of morphological defences may reduce predation losses as these morphological changes may interfere with the catching and/or feeding process of the predator or may prevent an attack. However, despite a sometimes high genetic variation of traits (e.g., [39][40][41]), freshwater zooplankton prey show a variety of inducible defences in different traits, between species and between clones. The reasons for this variance may be manifold.…”

Predator‐specific responses of Moina macrocopa to kaironmones from different fishes

“…Cladocera is an important group of model organisms for studying aquatic ecology and evolution, and is a textbook example of inducible defenses against predators (Lampert, ). Several Daphnia species display remarkable morphological changes in response to predators, including crowns of thorns (Petrusek, Tollrian, Schwenk, Haas, & Laforsch, ), spines (Tollrian, ), “twist” (Herzog, Rabus, Ribeiro, & Laforsch, ), and neck‐teeth (Christjani, Fink, & Von, ; Weiss et al, ). In addition to morphological changes, Daphnia exhibit predator‐induced changes in life‐history traits, such as size and age at maturity, size and number of eggs produced (Mikulski, Czernik, & Pijanowska, ), production of sexual eggs (Slusarczyk, Dawidowicz, & Rygielska, ), and changes in individual behaviors.…”