Light intensity controls anti-predator defences inDaphnia: the suppression of life-history changes

Abstract

A huge variety of organisms respond to the presence of predators with inducible defences, each of which is associated with costs. Many genotypes have the potential to respond with more than one defence, and it has been argued that it would be maladaptive to exhibit all possible responses at the same time. Here, we test how a well-known anti-fish defence in Daphnia, life-history changes (LHC), is controlled by light. We show that the kairomone-mediated reduction in size at first reproduction is inversely coupled to the light intensity. A similar effect was found for the kairomonemediated expression of candidate genes in Daphnia. We argue that the light intensity an individual is exposed to determines the degree of LHC, which allows for plastic adjustment to fluctuating environments and simultaneously minimizes the associated costs of multiple alternately deployable defences. It is hypothesized that this allows for a coupling of multiple defences, i.e. LHC and diel vertical migration.

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

“…The highly significant linear relationship between life history and behavior in the present study may indicate a cost tradeoff between them. A relation between behavior and life history in which they constitute mutually exclusive anti-predator strategies has been reported previously (Effertz & Elert, 2014;Slusarczyk et al, 2005;Slusarczyk & Pinel-Alloul, 2010). In addition, different types of responses to specific kairomones are coupled, the relationship could be explained by a fine energy distribution was evoked by predation pressure (Sakwinska & Dawidowicz, 2005;Tollrian, 1995).…”

“…Such behaviors include diel vertical migration (DVM) (Bollens & Frost, ), phototaxis (Ringelberg, ), swarming (Pijanowska & Kowalczewski, ), and escape reactions (O'Keefe, Brewer, & Dodson, ). A previous study revealed that changes in life‐history traits and individual behavior in response to predator stress exhibit a mutually exclusive relationship in Daphnia (Effertz & Elert, ; Sell, ; Slos, Meester, & Stoks, ; Slusarczyk & Pinel‐Alloul, ; Weider & Pianowska, ). However, the relationships among different defense traits remain unclear.…”

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

“…Miyakawa et al (2010) sampled animals over a time period of 24 h starting with the hatching of the juvenile Daphnia and subsequently pooled all RNA for measurements of relative gene expression, whereas in this study, animals were sampled within an hour of hatching. The narrow time window chosen here is in accordance with the finding that fishborne kairomones have been shown to induce upregulation of a specific set of genes in Daphnia in a time frame of only 2 h (Effertz and von Elert, 2014). It was reasoned that, as neck-teeth induction takes place during the late phase of embryogenesis (Parejko, 1992), gene expression differences should be most prominent directly prior to the hatching of juveniles from the brood pouches of their mothers.…”

Carapace epithelia are rich in large filamentous actin bundles in Daphnia magna, Daphnia pulex, and Sida crystallina (Crustacea: Cladocera)

“…If the stress fibers in the pillars of D. pulex are primarily contractile, ACT2A and ACT2B may be the predominant actins incorporated into their arrays (Fig. In two separate studies in D. magna the abundance of an actin transcript identified as act3, as well as pillar diameter, increased in response to predator kairomones (Rabus et al 2013;Effertz & von Elert 2014). In two separate studies in D. magna the abundance of an actin transcript identified as act3, as well as pillar diameter, increased in response to predator kairomones (Rabus et al 2013;Effertz & von Elert 2014).…”